Synthetic vs. Regular Oil
 

I have seen various claims about synthetic vs. regular oil. An article in the local newspaper stated a 20% improvement in fuel economy; it is also claimed that synthetic oil's change interval is twice that of regular oil (3000 vs. 6000?).

Do these claims hold water? Is synthetic oil worth the additional cost? Would it be worth my while to use it in my '92 VX? Let's face it. I'm such a miser that I'll try just about anything within reason to boost my fuel economy even further than my present 46-47 mpg (other than ridiculous infomercials :D ).

Usually I have seen claims of 1-5% increase in gas mileage when using synthetic oil. I went from regular to synthetic, and I haven't seen any difference that I can attribute to synthetic oil.

I change mine at approximately the same intervals as I would regular oil...3-5k depending on other life pressures. What I have noticed is that my intervals where I need to ADD oil seem to be getting longer...

JB, how in the world do you get 21 mpg out of a Cadillac Eldorado? Just curious.

I run synthetic in all of my vehicles. When I ran conventional oil I changed it every 3,000 miles. On synthetic I go every 5,000. I can probably go farther, but I find it convenient to get my oil changed when the mileage is divisible by 5,000. It is easy to remember when it needs to be done. For example, I did my last oil change on the Beast at 150,000 miles. I know when I get to 154,500 I will make plans to take it in for an oil change within the next week or 2.

-Jay

Hadn't thought about the change in intervals. I use 3k with regular oil right now, and it's handy to keep track of tire rotations; I rotate tires every other oil change (6000 miles per switch). Going to 5k would throw a monkey wrench into that...6k would work just perfect. Could always get some of those window stickers to keep track.

I always do my oil change and tire rotation at 5,000 miles. Its just easier for me.

-Jay

I did a 20k mile test with 5w-30s. One was M1, the other was Quaker State conventional.

10k miles each, over all conditions each, over all seasons each.

The difference wasn't even a full tenth of an MPG.

I change at 5k mile intervals and don't really like to go further. Modern conventional oils are pretty darn good now. I don't think I'll buy any more synthetics.

Your newspaper writer is on crack. Those claims are ridiculous.

You can check out BITOG, the generally accepted authority on oil, for more information than you ever wanted to know.

I use synthetic in my VW because it's what the manufacturer designed it for, so I wouldn't expect it to do so well on dinosaur juice -- and anyway, VW specifies 10,000 mile oil change interval on synth, no way I'd want to reduce that! :) In my other vehicles I use dinosaur juice at the manufacturer's recommended interval (in my truck, it's when the "Change oil" light comes on, at 5 to 8 thousand miles).

I've never had an engine fail or wear due to insufficient oil habits, and I can often be forgetful, cheap, and careless about it. I don't even KNOW anyone who should have changed their oil more often or used better oil. I suspect that most cars go to the junkyard without any problem attributable to oil habits, even if the owner didn't have good habits.

I've been working with synthetics for about 25 years. From my personal experience and a fleet I managed for 5 years the gains varied from 1.5-8% depending on winter/summer and/or short trip versus highway driving.

Bottom line is yes, synthetics can give some added mileage.

Per extended drains? Absolutely, no question. The length will vary on the type of oil used, the type of driving done and to some extent the vehicle.

Most of my personal equipment gets an oil change once a year which is on average about 10K miles and I also use a synthetic based filter versus the cheaper or OEM filter when possible.

Will synthetics save you money? In my case it does.

One thing too about synthetics is we simply use less oil & fewer filters to clog the landfills where recycling filters isn't available.

It can depend on the mileage and type of driving you do. This should be handled on a case by case basis. To many variables are involved to make a blanket statement.

1. I drive the car mostly on the freeway.
2. I keep between 55 and 60 as much as possible.
2a. Don't tromp on the foot feed.
3. Run 42 psi in the tires.
4. Relax (don't let others get my goat).
5. No A/C. Broken. The wife, however, is after me to fix it, so that will change soon.
6. Coast whenever possible.
7. Draft (at a safe distance, of course...if there is a choice between gas savings and safety, safety should come first) whenever possible.
8. This is an '83 Eldorado...3800 lbs (smaller by far than the old school Eldos), and a 250 cu. in. engine instead of a 500 cu. in. engine. Also overdrive transmission, and lock-up torque converter. The car was designed to get better mileage.
9. Always use the fuel economy readout...keeps you mindful, if nothing else.

According to the readout (the car comes with a sort of stone-age scangauge built-in) on trips to LA and back I have been getting about 25 mpg...mileage drops with a few trips in town to the grocery store...

The car, as it stands, is an aerodynamic nightmare (except for the really sloped windshield)...I've wondered how it would do with some streamlining...

Was rushed for time last night & I should add something.

During my years of fleet maintenance it was found the biggest mileage gains, thru oil useage was in changing all the drive line fluids to synthetic.

In every case where we changed all the drive line fluids to synthetic gains were realized. The biggest gains were seen in the winter, which common sense should suggest as well when doing a proper flush to synthetics in both the trany and final drive for units that had both.

We also used synthetic grease on wheel bearings that weren't sealed and synthetic oil in hubs that required oil baths.

This fall I'll be flushing the trany on our 5 speed Kia Optima 07 vintage W/I-4 that has been averaging 38 MPG at 65 MPH on the Interstate during fair weather. Should be interesting to see what this does. I doubt if the gains will be dramatic since most of the miles logged are on the highway but other benefits will be obtained with the change over.

I've never used synthetic, but have always used regular 10w40 of various brands changing it at 3K-4K intervals. Over the life of the '88 Escort with 477,000+ miles I would say I have changed brands 5 or 6 times so I don't think there is much difference in conventional oils.

yeee gads - that's about 120-160 oil changes . . . lets see if you ran Synlube you would have changed it 4 times.

Now at 17868 miles on Synlube and still running great with one oil change.

You're going to leave the same oil in for 100,000 miles? Not me!

I think most believers change their filter on a regular basis and replace however much oil came out with the filter.

I've also heard of people doing this with conventional motor oil, but I never had the nerve to try it.

I've heard of the opposite... Changing the filter with every other oil change. I'd never do it though.

-Jay

I obtained slightly over 20 in my 89 Cadillac Eldorado. If only I could have fewer left hand turns on the way home and more highway miles.

This actually part of the maintenance routine in some cars now. Honda is one.

Even if the filter was still "good" I don't like the idea of mixing 4 quarts of fresh, new oil with 1 Qt of old, used oil... I'm really anal about my oil changes. I always pour 1 quart in the top of the engine, and let it run until clear, then reinsert the drain plug. I also fill up my oil filter with oil before installing it too.

-Jay

In general synthetics do seem to improve FE some, however 20% seems to be on the high end of things. However, it might be possible to get that much FE gain from a synthetic if/when the higher quality synthetic also lets you go with a lighter (lower viscosity) oil. And better oil filtration also can help with FE (by keeping more of the friction causing dirt out of the oil), so if you take the opportunity to use premium/expensive oil filters with the synthetic, that could also help factor into the FE. i.e. Synthetic oil and premium oil filters can potentially help FE these ways.

1) In general synthetic oils run a little easier, and are a little more "slick" (then conventional oils) at the same oil weight. Both of these factors tend to cause a minor (maybe a few percentage points total) gain in FE over a conventional oil. OTOH while a few percentage points gain is apparently common in this area, some have reported no gain at all at this level.

2) IMHO you really should use premium oil filters with synthetic, as one of your biggest enemies (for both FE and the length of time the oil can safely be used) is dirt in the oil. So why put in expensive synthetic oil that can last a long time, and then cut that benefit short by conventional oil filtration? And again, good oil filtration will often make a little difference in FE, by lowering engine friction by dirt in the oil.

3) And its common (and fairly safe) for quality synthetics to go with a "cold weight" (1st number, before the "W") lower than the conventional oil. i.e. instead of using 10w30 oil (or 5w30 oil), you may instead use a 0w30 synthetic. This is safe because almost all oils are too thick when first starting out (i.e. the "cold" setting), but the lower first number is still less thick (when "cold") then the more conventional oil weights. And because of the quality ingredients used (in the synthetic oil mix), a good synthetic can have a wider temp range than a conventional oil and still be able to hold up to abuse. Which is why you might as well go with a "0w" oil (vs the 5w or 10w oils you are used to) if/when you switch to a synthetic (as doing so shouldn't harm your car any, and it will help FE a bit until the car gets up to temperature).

4) And some have even taken the fact that synthetics generally hold up better, to go with a lighter weight oil AT TEMPERATURE (to help FE even more). For example, my CRX was originally speced for 5w30 conventional oil. However, I currently run a mix of 0w30 and 0w20 synthetic in it. i.e. At temperature, I'm probably getting about a 23 weight synthetic, instead of the 30 weight my car calls for. This means I get slightly less friction (and therefore slightly better FE) after the engine warms up (over a normal 30 weight oil the car calls for). However, it also means that I risk having a "too thin" oil that isn't sufficiently doing the job and will therefore cause extra engine wear. In my case, I happen to think that the extra ability of the synthetic to not get thinner as it wears out (unlike conventional oils that do thin out as they wear out) keeps me sufficiently "safe" against problems. And I also monitor this issue (with oil analysis testing) occasionally (and so far so good). But keep in mind that (unlike lowing the 1st/cold number) lowering the 2nd/hot number is not without its risks (as it is possible to get an oil "too thin" for it to do its job in the engine)! But if you can safely lower this number, it will help a bit with FE.

So yes, if/when you factor in the FE gains from all of the above, it might be possible for it to be as high as 20% gain. But in general the gain will be less than that. Which doesn't mean that switching to synthetic isn't a good idea, or that it won't help. It just might not help as much as that article suggests.

It varies a LOT with the quality of the synthetic (the quality of the synthetic oils vary even more than the quality of conventional oils), but in general synthetic oils are much more prepared to hold up over longer driving intervals. In fact, I've currently got over 14,000 miles on my synthetic oil mix.

BUT, you will only really get long OCIs (Oil Change Intervals) if you combine quality synthetics with premium oil filtration. Because most oil filters on the market leave a LOT of dirt behind, and that dirt will kill your oil long before other factors. So if you really like the idea of 10,000+ mile oil changes, you really have to use both quality synthetic oil and quality filters.

If you do things correctly, the fewer oil changes will actually make the cost LESS than you would do with conventional oil.

i.e. Each oil change will be more costly, but you will need to do fewer of them, making the cost per mile (of the oil changes you need to do) less than the conventional oil (but more frequent oil changes) approach.

So when deciding upon synthetic or not, you really have a "pay me now" (more expensive synthetic oil changes now), or "pay me later" (more total cost of conventional oil changes, due to more of them being needed) decision.

I don't see why not. I'm using a mix of quality synthetics in my 91 CRX for example. However, how well it will work will depend upon which synthetics and filters you use, and also if you clean the engine of crud before switching. If I was doing it (knowing what I currently know), I would:

1) All oils work better in a cleaner engine, but this is especially true of synthetic oils. So I personally would first clean the engine using the Auto-RX product ( https://www.auto-rx.com/ ) as directed (and yes, you need to use conventional oil while doing auto-RX cleaning, as synthetic oil tends to interfere with the auto-rx cleaning process).

NOTE: There are cheaper engine cleaning products on the market, but I like auto-RX because (unlike most other products) it cleans while maintaining lubrication (i.e. it's a much more "gentle" cleaning product, with much less risk of harming your engine while cleaning).

2) If your car calls for 5w30 oil, switch to the premium 0w30 oil (for both technical reasons, and personal experience, I'm most fond of Amsoil's synthetic, but then again I'm technically an Amsoil dealer so I'm not unbiased).

3) As to oil filters, get the best filtration on the market (to keep the dirt out), which for most vehicles seems to be Amsoil's EAO line of fully synthetic media oil filters (and no that's not just Amsoil hype, it's been independently tested by various folks).

4) Keep an eye on your oil levels, adding "make up oil" as needed. Since synthetic oil runs easier, you often lose oil quicker with synthetic, especially when you first switch over. Also, as you make your OCI (Oil Change Interval) longer, you have a longer period of time to lose oil (i.e. few cars lose enough oil over a 3000 mile oil change to cause harm to the engine, but most cars will lose enough oil over 10,000 miles to harm an engine). So keep a periodic eye on your car's dipstick, and make sure you keep the oil level up to where it needs to be (i.e. add "make up oil" as needed, to keep the oil level up).

5) And it wouldn't hurt to make the first couple oil changes (with full synthetic oil) shorter OCIs than you will eventually go with, to give the engine a chance to get used to the differences (in lubricating and cleaning properties) of the synthetic over the conventional oil you have been using. Because while synthetic is generally better (some in the industry debate if its enough better to justify the cost, but few argue that synthetic is an overall better oil), it is none-the-less "different" (in how it cleans and lubricates) as well. And since machinery can get somewhat used to the properties of the fluids you use, its helpful to stress things less hard during a "break in period" (in this case getting the engine used to the properties of the synthetic oil you use). Since almost all oils work best when "fresh" (first put in), the easiest way to accomplish this goal is simply to make the synthetic oil change intervals shorter at first (so as not to depend upon the full benefits of the synthetic, until the engine is used to that mix). For example, I might change out my 1st synthetic oil change at roughly the same mileage as conventional oil (i.e. the 3000-5000 mile range), boost up my 2nd synthetic oil change to maybe 7500 miles, and only go 10,000+ miles on the 3rd+ oil changes with a good synthetic.

NOTE: I'm technically an Amsoil dealer (even though I'm currently buying more Amsoil stuff for myself, than I am for the few "customers" I have). However, (being a dealer) I would be happy to help Gassavers members with discounts (on Amsoil products). So give me a PM should you decide you want some Amsoil products (such as their synthetic oil or filters).

I already run 5W30 synthetic in the Beast, and 10W30 synthetic in Rusty and The Buick. I may consider switching the Beast to 0W30 and see what happens with my FE since I do a lot of short trip city driving. It may increase my city mileage. I'm not due for another oil change (5K) for about 3,500 miles yet though... I figure that will probably be late summer/early fall unless I take the Beast on a roadtrip. The Beast is my highway crusier. It is so comfortable to drive. With the ample legroom and headroom, power seats, power adjustable lumbar support, tilt & cruise you can almost sit back and let the truck drive you there :)

-Jay

IMHO you have little to lose by doing so.

Yes, the higher FE (and lower engine wear) from using a 0w oil only helps for a few minutes (i.e. once the oil and engine are up to temperature, its the "high number" that dominates the FE effects), But since we all have to start our cars sometimes (especially if you make a lot of short trips), we all do end up having some of our driving dominated by the "warm up period" (and therefore also dominated by the 1st/lower number of our engine oils).

NOTE:
With conventional oils, you have to be careful about going with a too wide viscosity range (difference between the 1st and 2nd numbers). This is because the traditional "viscosity modifiers" techniques used to get a wide temp range with conventional oils actually make the oils "weaker" (more likely to wear out quicker, especially when abused). So with a conventional oil, something like a 10w30 (20 point range) actually still makes a little sense (as it will stand up better than a 5w30 conventional, much less a 0w30 conventional if you even could find/purchase that).

However, most synthetics aren't made using the traditional "viscosity modifiers" that conventional oils use (i.e. different techniques are generally used to make a wide viscosity range in a synthetic). As a result, many synthetics can have a much wider temp range and still hold up to a lot of abuse. And since a wider temp range in a synthetic doesn't typically pay the same "price" (of much quicker wearing out of the oils) that conventional oils suffer from, going with a quality 0w synthetic pretty much gives you all the gain with none of the down-sides (that a 0w conventional oil would have).

BTW: The "holy grail" of multi-viscosity oils, is an oil that maintains the same thickness at any temperature it will be used under, and we aren't there yet. i.e. Even a quality 0w30 synthetic oil, while much less thick "when cold" than a 10w30 oil, is none-the-less still thicker cold than when it warms up to temperature. However, the research seems to be moving us in that direction. So eventually, we might end up (some day) getting an "oil" that is the same thickness at -30F that it is at 260F (or any temperature in between). And ideally, that sort of "constant thickness" oil (that runs the same no matter what the temperature is within its operating range) is what we ideally would like for an engine oil for our cars.

Makes sense to me. After all, why do another oil change right now, when you can (instead) get some more life out of your existing oil (and just change products at the next oil change)?

Actually I will probably leave the "oil" in for 150,000 miles and change just the filter 2 more times. Keep in mind that Synlube is NOT oil so the same rules do not apply. Next filter change is at 36,000 miles maybe sometime next year.

I used to change the filter every other time - they held less than a quart - I cranked the engine over a little when the drain plug was out to empty the filter a little. Cars alway rusted away before any engine failure occured and that was with 6-8k change intervals and oil filter every other change.

Now I don't have to change it at all . . . seems really weird . . . the "oil" level also doesn't seem to be going down at all either.

Not that I would blindly suggest re-using a filter. It was simply a "matter of fact" statement as to what some of the auto manufacturers are now doing.

However, in our fleet we did re-use our Amsoil filters for 2 oil change cycles to see what harm would be involved. The vehicles used for this were the late 90s 5.7 Ltr. GM V-8 with over 100 K miles logged, mostly highway driving.

To make a long story short.

The process involved dumping the filters on 2 vehicles and leaving the 1/2 or so qt. of oil in the filter on 2 others. In all cases very little difference was seen in the used oil analysis between the 2 after 2 oil changes. On average the vehicles were hitting 20K miles before the filter was ditched.

Much of the above was due to the synthetic filter used, which the current filter is far superior to what we were using a few years ago.

Again, this was an experiment that yielded favorable results yet Honda and some others are now doing a similar procedure but not dumping the used oil from the filter. Again, just a "matter of fact". I am though doing a similar experiment on a car that has nearly 150 K miles by using an Amsoil EAO filter thru 3 cycles.

We also pre-filled filters during services, used or new. This I still do on my personal equipment and it only makes sense. Many think it's a waste of time that I'll strongly disagree with.

As per dumping fresh oil thru during a change, not enough exposure is given to flushing out internal passage ways and surface areas to make this of any benefit but to each their own.

More info can be found on my home page about lubrication and I'll update as time allows.

Going to 0W30 synthetic from 5W30 conventional oil was worth between 5 and 10% on Wile-E. I "only" used the cheap walmart/supertech/tech 2000 synthetic and discovered it was amazing stuff. I put 10,000 miles on the one change, and it looked, smelt, felt like I'd only just put it in, and through the whole change interval it maybe went down the stick an 1/8th ... and half of that useage was probably me wiping it off the stick every week :D

Synthetic is different than conventional oil in that it fails in the opposite manner. A 5W30 synth is a 30 weight oil with viscosity modifiers that make it runnier when cold. When those wear out, you've still got a 30 weight oil protecting your motor at high temps and rpms. In a conventional oil, a 5W30 is a 5 weight oil with viscosity modifiers that thicken the oil up when it's hot. So when those wear out, you're left with 5 weight oil when your engine is warm and needs the most protection.

As regards power increases, and we may infer economy benefits, David Vizard, a well known author of performance books, says he dyno tested synthetics and conventional oils and various blends and discovered that all the power benefits are there with only 25% synthetic in the motor. So if you have a motor that uses or loses oil, and synth is too expensive to have to keep topping it up, you could try just a quart of synth in a change. (presuming your changes are about 4 quarts) Theoretically then, you'd see the same gains as running full synth. This may go for powertrain fluids as well., but remember a pan drop and fill only gets about 50% out and typical capacities are in the 2 gallon range, so you'd want 2 quarts of synth fluid in there.

However, leaky smoky motors have a better option, "High Mileage" blend oils, these I have found, run very nicely and reduce smoking and burnoff significantly, you can cut your consumption to a quarter or less. They have seal conditioners also that really seal up. No "snake oil" I've found is even half as good as these oils. In fact most of those I have observed to sludge a motor up, the HM oils clean it!. These are also usually a synthetic blend, and will give you better fuel economy than sticking in 20W50 and 3 cans of thick goop to try and get your smoking or leakage under control. If you're just burning oil and not leaking any, then consumption is likely to slow a lot with a straight synth, because they resist burnoff a lot better. The detergent propertied in synth or HM oils may also unstick rings, which may be causing a smoking problem, whereas "snake oil" type stuff will just keep adding to the problem by building up the carbon trying to seal it that way.

I bought a lifetime billet aluminum oil filter with stainless steel mesh and 1000psi bypass for my 3000gt vr4. Took out the synthetic oil and put in Shell Rotella 15-40. Was $8.88 at Walmart but is now $9.37 for 4 quarts. I can remove the filter and basket and clean it and reinstall it without any leakage. I do this about every 1000miles. Went from 4 lbs pressure to 16 lbs pressure with the new filter.
Paid $219.00 for it. I found it at a race shop in Huntington Beach that supports Bonnieville race cars. It works great.

While going through college I worked at a gas station in ND. One really cold night a lady asked me to put some oil in her car for her. I grabbed the oil from her trunk and tried to poor it, but it wouldn't come out it was so thick! I ended up exchanging it for a warm one from inside.

I decided to do a test that night. I took a container of 5w30 quaker state and a quart of 5w30 mobil 1 and put them outside. After a while I checked them with our thermometer and they were both -15 degrees F. The quaker state was so think you couldn't get it out of the bottle (much like I had seen earlier). The Mobil 1 was thin enough that you could still get it to slosh in the can.

Ever since then I have run Mobil 1 in all of my vehicles (without problems). I have watched it cure cold weather starting issues on lots of vehicles including cars, motorcycles and diesel trucks. I also had 2 early broncos. I had put Mobil 1 gear lube in one, and the other was dyno oil. At -10F I could easily push the one with Mobil 1, it took 2 people to move the other one. This was inside my storage shed on flat ground with the transfer cases in neutral, so the only appretiable difference was the gear lube.

So, its not a bad idea to run synthetic oils all around, but there is an unquestionable gain to be had for those who live in the frozen north.

Mr_C in MN

You might have to get used to it, many of the new type motorcycles, watercraft, boats,and autos that now use a dry sump type of lubrication system , it is all but impossible to get out all the oil , in a yamaha that holds 4.1 quarts the most you can get out even with a filter change is 3.3 to 3.5 quarts leaving 1/2 quart of used oil in it.THat is why in those vehicles they only use sythetic oil and stick to regular maint.I cant off hand name the autos that come with this type of dry sump system, but it definately is the route of the future ,as more and more are switching to it, as the oil is cleaned cooled.Hey just an obsevation,arent most sythetics still made from petroleum ??>Marvin

I may have to deal with it, but it doesn't mean I have to like it... :D

-Jay

amsoil and mobile 1(fully synthetic) use a PAO(poly-alpha-olefin) base, which seperates them in quality from petroleum base oils.

this link is long, but you can scroll down to the synthetic section.

https://www.calsci.com/motorcycleinfo/Oils1.html

Actually, I thought Mobil 1 was one of the first Synthetics to switch away from being true synthetic (PAO) to highly processed dinosaur juice.

From your link above:
(Emphasis added) (Hey, he calls it dino-juice too! :) )

mobile produces both, trying to attract all consumers(believers and non-believers of synthetics) presumeably. and of course a variety of pricing(quality) is subsequently offered.

it's been said that of the fully synthetic oils, amsoil uses the best and most expensive PAO base however.

According to your own link, Mobil does not make a true synthetic PAO-based oil.

very interesting! i must admit, i do not buy mobile 1 any more.

it used to be as follows:

mobile 1 5000 and 7500 were synthetic blends. if it had a guarantee of 10k miles(or more), it was a full synthetic(presumeably PAO based).

if this is true, i have no reason to go back to mobile 1!

I run syn and a mopar factory filter in one vehicle With 4.500 - 5,000 mile change intervals. All other fluids (both diff's - t case and tranny are syn also from the factory). I changed the motor oil over to syn at about 9,800 miles after sufficient engine break-in. No noticable difference in gas mileage. I have used both Mobil 1 and Valvoline syn which are both brand names. The Valvoline is less than $20 for a 5 quart jug.

My other vehicle gets dino and a ac delco filter since the day it was new. (150,000 or so miles on it). It will keep getting dino. I usually buy quart bottles since it takes 4 1/2 quarts and the oil cost is somewhere around $12 or so depending which brand and if it is on sale or if I buy a case or what.

I always do my own maintenance - and there is not that much cost difference for whatever that is worth.

While I do believe that syn has superior lube qualities and less friction I really saw no difference in gas mileage.

Your results could vary, depending on the variables involved. This is just my experience with dino and syn.

I run Amsoil and gained 1.5 MPG in my 01 Chevy Impala!