So how much oil for best fuel economy?

[philmcneal]

What is the usual recommended amount of oil to use in your car? Isn't that recommendation for the "average" driving conditions? What happens if my driving conditions are unique from everyone else? (Never heavy throttle, never going past a certain rpm, coasting with no engine (cools down the engine no?), having engine off at a stoplight and restarting it with the key, and driving like I have no brakes (when I can).


Basically I drive for mileage and I heard that some people (like Wayne but I haven't heard it from his own words yet) that you only need half a litre to fully lubricate everything. Now is that true??... because usually the factory recommended amount is 4 to 5 litres, and if I only put not even half of that... aren't I risking a lot? Sure the engine doesn't have heavy oil to drag along with the car, but now it doesn't have enough lubrication to fully protect itself! How do I know the balance between enough and too much? My friend said something about the engine getting too hot and expanding to the point where not enough oil cannot protect it and that amount (1/2 litre) is totally ridculous. Even if you try to dip stick your stick to check the oil, none will even be displayed!


Hm...... I've been a sucker to Honda service since from day one since I owned my car. (I'm extremely noob when it comes to car maintainence) They always used some bulk 5-20W oil and now I just got myself some Mobil 1 0-20W at a expensive price. (4 litres for 40cnd) I've never done my own oil change before and it looks like I have to if Honda won't accept my specifications. (Blah blah about warrenty and such, even if I try to convince them I don't drive like they do)

What's a fuel economy nerd suppose to do ;(? Did you guys managed to go to a car service shop and managed to convince the workers there to do the way you want it to? Damn I hate how this world was set up!!!


Thanks for reading guys! I appreicate it

[krousdb]

Originally Posted by philmcneal

Basically I drive for mileage and I heard that some people (like Wayne but I haven't heard it from his own words yet) that you only need half a litre to fully lubricate everything

I'd be interested where you heard that 1/2 liter is sufficient. I haven't heard that from Wayne.

I don't understand why using less oil would effect FE. As long as it is not overfilled, there will be no difference in FE if you use 1/2 liter or the recommended amount. In fact, IMO it will be worse because your engine will not be fully lubricated.

[JanGeo]

From my personal experiance what happens if you run the engine low on oil is on a high G turn the oil pump with cavitate meaning that the oil in the pan will flow up the sides of the oil pan and engine and the pump pickup will suck air. It will also happen on a steep hill and while braking and accelerating hard. Oil also provides cooling to internal parts not reached by water in the cooling system - and that relies on having the oil at a low temperature - the "extra" oil in the pan allows the oil to cool a little before it gets pumped back through the motor. Running low on oil reduces the time it has to cool in the pan and may cause an overheating problem. Guess what cools the pistons . . . oil sprayed up from the wrist pins and crank bearings!

Run a liter low and you can get away with it - rabbit held 3 quarts and I used to run it down to 2 quarts before an oil change (including filter). Geo was the same and no harm.

If you are running Mobil One you can leave it in longer and maybe change the filter without the oil change as the filter clogs and has zinc in it to neutralize the acids in the oil which gets expended after a while. Only sure way to know it to TAKE A FILTER APART after you change it to see how dirty it is.

[n0rt0npr0]

Okay first off the half liter thing is silly, anyone can go to the junk yard and just by glancing at ANY post 1970's vehicles oil pan you will see where a half liter will put you. It's got to submerge the oil sump. Half liter won't do it unless your total oil capacity is around 1.5 liters.

I'm not worried where that half liter rumor came from at all.

Since the 70's ended, 99% of engines no longer have crankshafts that dip into the oil. Therefore reducing the amount of oil in your pan by, I'd guess, 35% will have no effect from the old school "crank dips into the oil" theory. This one still gets passed around like candy.

However I do know from testing that oil pressure WILL drop the lower you go on your dipstick. There is a minimum of oil pressure that the engine will need. If you can get that number, and you have an oil pressure gauge on your dash (or have access to one) you can increase FE.

There are jets of oil that spray the crank down for cooling purposes. Well its more complicated than that, but I don't want this post to be too long....
If you reduce the pressure on those jets then you reduce the size of the explosion that occurs when the crank "collides" with the stream. That collision is the biggest thing that creates oil vapor, and the less oil vapor you have in the crankcase the more "freely" the crank will spin. Less oil vapor friction = Fuel Economy.

Anyway, the improvement you can get from this very very sensitive test and hence modification is vehicle dependant. When I had a vehicle with an oil gauge I got 4% improved FE from this.

Yeah I won't mess with that again really, testing took too long and because I've never had the fortune of scangauge how can I pinpoint that my mod was even the cause. Anyway, I figured out below 2mm of the "add" oil mark on the dipstick was the sweetspot. Below that made the pressure too low and inconsistant.

After the testing I am doing I'll be back with a new thread on how we can "safely" increase FE with a heavy modification to our engines.

You taking that step and doing your oil change yourself with synthetic is bound to get you some more FE!

JanGeo! Great post complimenting mine! But running the oil low will not directly contribute to overheating. It will overheat the oil and hence not last as long. Only by sucking air and starving the oil sump will you have an overheating issue along with others...

[JanGeo]

However I do know from testing that oil pressure WILL drop the lower you go on your dipstick.

Lower the car not the oil level!!! LOL

Seriously did you have an oil temp gauge when you ran this test?? Never heard of the pressure dropping due to oil level in the pan.

[n0rt0npr0]

I did have a "coolant temp gauge." Never an oil temp as those are mostly for very large trucks if I am not mistaken.

And yes the pressure did drop in my testing. I can't say for sure why, but just maybe it was due to the surface of the oil being very close to the sump pickup and there was high cavitation present reducing the amount of dense clean oil in that area...verses the less dense cavitated oil.

[JanGeo]

The reason I asked about an oil temp is that it can run a lot hotter than water temp as it pertains to the piston side of the cooling system which as we know can get a lot hotter than the water cooled head side of the combustion. My thinking is that your oil temperature was getting hotter thus lowering the pressure and not from the lower level in the pan. Is why you should always limit your rpm when the engine is cold - the oil will not flow as easily and you are forcing the excess pressure through the relief valve to dump the excess oil flow back into the crank case pan.

Note some oil filters had a safety valve when the oil would not flow through them they would bypass the filter element.

[Compaq888]

I'd never mess with the amount of oil in the engine. The best way to go around this is to use some rare oils that have better lubrication=fuel economy.

Mobil 1 isn't exactly full synthetic, it's like half synthetic. Also the synthetic part of the oil only helps on start up.

It's been proven time and time again that it doesn't matter how much the car weighs(to a certain extent) if the car is airdonamic and the engine is tuned right then you'll get good mpg. Your biggest enemy is not the amount of oil in the engine it's the air around the car. I garantee it that you will see more improvement with airdonamic stuff than messing with the engine oil level.

[n0rt0npr0]

Mobil One is fully Synthetic. Synthetics are defined by the basestock and Mobil 1 is 100% PAO
Amsoil is too.
The others that use the most PAO is Royal Purple and Redline.

No one else is fully synthetic.

The diehard racing guys will tell you that the pour point is the sole indicater of a full synthetic. In that case, only Mobil 1 and Amsoil hit the mark of -54°C or lower...

[philmcneal]

oh ok, i just found out my real answer. It wasn't half a litre, it was fill between "too much and too little"


Had to search up old posts on greenhybrid to find me out that answer but thanks for the handful of replies! Half a litre would have been killer for sure!

Now the hard part is convincing honda...

edit: well honda says my km are too low for an oil change since mine is expected at 40000 km and I only have 36000 km on the odometer. Although funny its more expensive to provide my own oil rather than using honda's so when the time comes I'll get mine done at wal mart or something since they have cheap prices for providing your own oil.

At least the service desk guy was impressed with my mileage, and I told him my future mods. He thinks the savings are not that big enough to start driving like I do though but he was interested in improving the mileage of his Honda Pilot... unfortnately I had nothing to offer but what I know of my own car.