First Post. New car. Ways to increase mileage cheaply.

[GasSavers_w9awx]

Hey everyone. Finally got my wish after getting my truck stolen. I have bought a car that gets decent gas mileage. Now, this is no Prius or Civic VX, but for me, double the gas mileage is a big improvement.

Just bought a 1995 Eagle Summit DL, 1.5L 5 speed. The car only has AC for options, no power steering, which I actually haven't even missed. I am not looking at opening up the engine or anything big like that. What I am looking for is some basic ideas for improving my car's fuel economy. Here is what I am thinking. Feel free to add to my ideas.

1. baseline gas mileage on a highway drive this week. 31.4mpg doing about 80% interstate driving at 65mph.
2. looking at doing a full tune-up (plugs, cap, rotor, pvc, oil and filter, trans oil)
3. replace tires with new tires once the snow is gone and I can take off the snow tires. (originally P165/80R13, currently has P175/70R13 tires from the previous owner). Keep the same size or go back to the original size?

I have seem several mentions of pulse and glide. What is that? When I drive traffic is fairly light for a metro area so there are times and also some big long hills that I go down going to work that I could possibly use. Coming home, i change the route to go on a less hilly road, but, I use the same roads all the time for consistency.

Any other ideas inexpensive ideas? Not really into changing the bodywork. My driving habits will change with time, I am sure.

Gregg

[thisisntjared]

if the majority of your driving is highway or at least speeds of over 50mph then you should look into a few aerodynamic modifications.

but, i think, for now, the most fruitful thing for you to do is item 2. a full tuneup on a 10yr+ old car is usually the best thing to do, even if the car was decently cared for. dont forget to do both air filter and fuel filter, as both have quite an impact on fuel economy after a good many miles.

EDIT: and welcome to gas savers!

[theholycow]

Welcome! Congratulations on changing to a more practical vehicle. You don't need to have a Prius or a Civic VX to work on improving your fuel economy. You also don't need to worry about opening up the engine -- we don't do much of that sort of thing here. Manufacturers have done a pretty decent job inside the engine for a long time, and even on a 1995 model it's often not worth investing money in upgrades to engine parts.

Does your baseline represent your usual driving? Do you usually drive 80% interstate at 65mph?

Pulse & Glide (abbreviated to P&G) is a driving technique where you accelerate to a little faster than you want to go, then put it in neutral and coast until you're going a little slower than you want to go. This is more efficient for a few reasons:
- Engines produce work more efficiently under higher load (google for BSFC fuel economy for some measurements and explanations)
- While idling, the engine turns fewer revolutions for the same distance, so it loses less energy to engine friction
- P&G may result in a lower average speed, which means less energy lost to aerodynamic drag

Some people turn their engine off during the "Glide" portion of a P&G cycle, a strategy which I call P&EOC (Pulse & Engine Off Coasting). Some people mean that when they talk about P&G, others mean doing it with the engine still on.

Light traffic and long hills are good for P&G. Highway driving makes P&G difficult for me, because I don't like to go too slow or too fast on the highway, and also because the car loses speed much faster on the highway.

For lots of highway driving it may be worthwhile to do some aerodynamic modifications. It may be worthwhile to block part or all of your upper and/or lower grilles, which can help aerodynamically, can help keep under-hood temperatures warmer, and can maybe even increase intake air temperature (IAT)...all things that are known to increase FE (Fuel Economy) for some people.

A free modification is to increase your tire pressure. There's lots of info about it (how/why it works, safety, etc) in the tire pressure link in my sig. Basically, try increasing it from the car manufacturer's recommended pressure, but don't exceed the tire's rated maximum pressure as stamped on the side of the tire. Use the highest pressure that's comfortable and handles well and keep an eye on wear; if you get center wear, back off the pressure a little. For me, I always have good results at maximum pressure, except the rear tires on my truck which suffer from bad wet traction above 72psi.

Driving habits are where the biggest improvements can be made, and that's most of what we discuss here.

There are a couple links in my sig (a FAQ, and my "sig meta thread" which has lots of stuff including a link to my own intro to hypermiling) and a glossary link at the top of the page that can explain acronyms and techniques commonly discussed here.

[GasSavers_Pete]

Welcome from me as well.

Less wide tyres will both add to the aero benefits and rolling resistance as well so 165 would be my choice. Have a look for Low Rolling Resistance (Usually abbreviated to LRR) specs as well.
Also have a wheel alignment done as well and get an accurate tyre pressure gauge. Gas station ones are useless.

Take out everything you do not need to keep the weight down. Extra tools , spare parts etc. Leave them in the garage. Remove any thing obvious like ski racks , luggage boxes.
I know this is obvious stuff but it is astounding the number of people who have this junk attached.

Take the least hilly routes when you can and avoid peak traffic times of possible. Easier said than done but it can make a huge difference.
Before anything else , get a tune up done and replace the oil (if it looks dirty or if it is due) , filters , spark plugs , distributor cap etc.
Each take a little from the economy as they age.

Keep accurate records so you can tell what is working and what isn't

Good luck , Pete.

[Geonerd]

The tune up sounds good.
A good synthetic transmission oil is worth the extra few $. You should enjoy smoother shifting, lower wear, and slightly improved mileage as compared to standard MTF.

Syn motor oil is usually worth while too, for the same reasons. Personally, I'd stick with the mfg's suggested grade, and give the extra thin (0-20, 5-20) 'fuel saving' stuff a pass. If you dig around the BITOG used oil analysys results, you'll sometimes see slightly higher wear occurring with these mixes. M1 and Penzoil Platinum, among others, work great.

It won't hurt to set the spark plug gap a few thousandths wider. Some peeps report minor FE improvement.


Tires
Consider buying slightly taller tires, to lower the overall gearing of the car.
http://www.miata.net/garage/tirecalc.html
Mild overinflation will help FE. Inflate to around 5 PSI over mfg's suggested value and see how it rides.


Pulse and Glide works, at least for me.
The idea is to give the car healthy throttle (~40to ~80%) at low-medium revs, where the engine is most efficient, then coast or glide as far as possible (or until you become a traffic menace. ) Don't be afraid to slip the transmission into N, or just hold the clutch in when gliding down gentle hills or coming up to a stop sign, red light, etc. Starting and stopping the engine at every opportunity will certainly increase MPG, but at the cost of extra wear and tear on the car. Starters, ignition switches, and clutch plates aren't free, and the oil film that protects your engine's bearings collapses every time the engine is stopped.

Hills are not necessarily a bad thing, so long as you don't need to brake much on the downhill side. They can act as natural P+G-like energy accumulators. If you can arrange a long glide down a gentle slope, you're mileage will soar.

Anticipate traffic lights. You should keep half an eye on any stoplights ahead of you, and have some idea where they are in their cycle. The idea is not to predict the damn things with absolute accuracy, but to minimize the odds of needing to stop or brake heavily.

[GasSavers_w9awx]

I should have noted that it was a trip I had taken doing the 80% highway. My daily drive is about 80% city, 20% highway. Almost all on a divided highway with speeds between 45-50mph.

[theholycow]

A few things that I would disagree on, and why...

Originally Posted by Pete

Less wide tyres will both add to the aero benefits and rolling resistance

Tire width will help slightly with aero but may increase rolling resistance. Good data is difficult to come by, but the theory is that with a given weight at a given inflation pressure, you're going to have the same size contact patch; and if you make the tire narrower, that means the contact patch will be longer. The longer contact patch means more sidewall deformation which means more rolling resistance.

It was discussed at length in the tire width link in my sig, and the results were inconclusive due to some interesting data that others were able to come up with which shows that the real world effect doesn't necessarily match the theory. However, I'm not sure I know of a theory why narrower tires would help; I think that's always just been an intuitive thing that people think of, perhaps from remembering skinny-tired road bicycles (whose tires are narrow for entirely different reasons).

Take out everything you do not need to keep the weight down. Extra tools , spare parts etc. Leave them in the garage. Remove any thing obvious like ski racks , luggage boxes.
I know this is obvious stuff but it is astounding the number of people who have this junk attached.

While I agree that extra ballast should not be dragged around, I think the importance of weight reduction is far overestimated by most people. In my experience, and in lots of others' experience that has decent data behind it, it has zero effect; a few others have reported real gains with decent data to back it up. It seems that very lightweight cars with little power are the most likely candidates to improve from weight loss. There's a link in my sig meta thread about this, too.

Take the least hilly routes when you can and avoid peak traffic times of possible. Easier said than done but it can make a huge difference.

Actually, I agree with Geonerd on this one:

Originally Posted by Geonerd

Hills are not necessarily a bad thing, so long as you don't need to brake much on the downhill side. They can act as natural P+G-like energy accumulators.

but question this one:

A good synthetic transmission oil is worth the extra few $. You should enjoy smoother shifting, lower wear, and slightly improved mileage as compared to standard MTF.

Syn motor oil is usually worth while too, for the same reasons.

There's lots of great reasons to go synthetic, but if you do it for fuel economy I wouldn't suggest holding your breath waiting for it to pay for itself.

That said, I did spend more money on oil for fuel economy purposes in my last oil change. My car specifies synthetic, and instead of specifying a grade and type, VW has a test that oil must pass to be approved for use in their cars. I found one approved oil that was a 0W30 when most of the rest are 5W40, and spent a few more dollars on that oil instead. I doubt it has paid for itself and I have no way of knowing for sure.

Consider buying slightly taller tires, to lower the overall gearing of the car.

Good idea (for some cars, I don't know if it's good for the OP's car), but you got the terminology wrong. Taller tires make higher overall gearing.

[Geonerd]

Originally Posted by theholycow

A few things that I would disagree on, and why...

There's lots of great reasons to go synthetic, but if you do it for fuel economy I wouldn't suggest holding your breath waiting for it to pay for itself.

I didn't say it would save a lot!
IMO, I've heard enough anecdotal evidence of slightly increased mileage when running syn that I wouldn't rule out the possibility. I suspect synthetics display different shear vs. viscosity behavior, and that this may result in slightly lower drag at a given speed, temperature, and base viscosity.

Good idea (for some cars, I don't know if it's good for the OP's car), but you got the terminology wrong. Taller tires make higher overall gearing.

Whatever.....