What With Gas Prices Now Well Over Two Bucks a Gallon....

[CO Liberal]

...I'm looking for ways to boost my gas mileage. I drive a 2002 Chevy S10 with a 4-cyl engine and a 5-speed. I currently get between 25 and 27 MPG on the highway, which is where I do most of my driving.

With a daily commute of close to 100 miles a day, any improvement in mileage would be appreciated. Anyone know of anything that actually works to boost mileage?

[Orsino]

1. Drive more slowly?

I'm trying to maximize the mileage in my Prius, and am breaking myself of the left-lane habit. I'm using gradual acceleration, too, and MPG is creeping toward 50.

Higher-octane fuel may help?

[CO Liberal]

4. I Filled Up With Unleaded Plus This Morning

I'll see in a few days if my mileage improves.

[Orsino]

10. Might Slow Engine Wear, Too?

I've never heard anyone confirm my theory, but I figure that if higher octane means more power per gallon, we burn less fuel to do the same work. That would have to be better for the engine, wouldn't it?

[HamstersFromHell]

12. Actually, higher octane just burns slower...

It contains more "anti-knock" ingredients (used to be more tetraethyl lead before the unleaded days of now) to slow down the combustion a bit.

Higher compression engines (or older ones with not very efficient cylinder head designs) need a gasoline which won't literally "explode" in the cylinder...that's a "knock" or "ping" and can do serious damage to the engine.

Gas additives to raise the octane merely prevent the explosion from happening...it spreads as s smooth flame front from the spark plug outward.

Now what you say is true if you vehicle needs a better grade gas to begin with...the smooth burning is more efficient than knocking or pinging your way down the road.

[trogdor]

13. Not exactly.

Gasoline is a blend of various closely-related hydrocarbon molecules that have different characteristics when burned. The correct ratio of these causes more complete combustion, and thus the most "bang" for your buck. There is an old Standard Oil film over at archive.com that explains it, using a ball-peen hammer and a rubber hammer to explain the difference. When you kit the piston with the hard steel hammer, it only moves a little bit, but when you hit it with the rubber one, the energy from the impact is more completely transferred to the piston and it moves a whole bunch of times.

Octane number merely refers to the energy potential of the fuel.

[HamstersFromHell]

2. Not necessarily driving slower, but...

...driving at the engine rpm that is it's torque peak. That's the "spot on the tach" where you engine is at it's most efficient. Of course, this only applies to vehicles that are reasonably aerodynamic to begin with. :)

Of course, all the other tricks apply...

Don't use your a/c. Same applies to defrost on GM cars, as it briefly runs the a/c compressor.

Keep windows rolled up - in many cars the aerodynamic drag of a window down hurts mileage more than running the a/c does.

On pickups, if you don't have a camper shell or tonneau cover, opening the tailgate or removing it in favor of a cargo net will greatly reduce aero drag from that big empty "box" you're hauling around.

Inflate tires to the high side of recommended pressures. Most cars on the road nowdays run on underinflated tires through negligence of their owners. Not only does it cause premature wear to the tires and an increased chance of major tire failure due to heat buildup (see Ford Explorer), but it hurts mileage as it increases rolling resistance. Most any car can get a bit more mileage by running tires in the 32-36psi range instead of the "nice riding" 26-30psi recommended. Ride will be a bit rougher, but you may actually like the way the vehicle feels as it'll also be more responsive to steering input.

Use the lightest grade of motor oil your vehicle manual recommends. If you can use a 10w-30 instead of a 10w-40 or 20w-50, do so. It decreases internal engine drag by lightening the viscosity of the oil when the engine is warm.

Accelerate smoothly and brake smoothly, of course.

Do not let your vehicle sit to warm it up. Get in, start it up and let it run 30 seconds to get oil circulating, then start driving. I Hold engine rpms down less than 1/3 of redline until the water is up to temp., then use no more than 2/3 of redline for another 10 minutes until the oil is fully warm before ever using the redline or anything near full throttle. Note that this isn't so much saving fuel as saving wear on the engine. The quick warm up will save gas over letting it sit till it's fully warmed up, as with no load, the engine warms up very slowly.

Hope this helps!

[CO Liberal]

3. I Do Most of That Stuff Already

I'm getting the oil changed tomorrow, because my wife and I will be using the truck to drive to Texas next week. I'll make sure they use either 5W-30 or 10W-30, and set the tire pressure to the top end of the range.

I have a camper shell, and I'm thinking of getting a bug deflector - I'm wondering if that will reduce drag, since the shell sticks about an inch above the roof of the cab.

I filled up with Unleaded Plus this morning. It cost me about $150 more to fill the tank, but I want to see if I get meter mileage with the better gas.

[HamstersFromHell]

5. Don't know about the bug deflector, but...

mounting a similar deflector on the top of the roof right at the windshield might help a bit. (Similar to what semis use to "flow" the air over the trailer.)

One other thing I didn't mention before that will make a difference.

Buy some Chevron Techron fuel injector cleaner. I've tried a bunch of others and none seem to work worth a damn. It's pricey compared to the other brands as well (about $7.00 - $10.00 or so for a bottle to treat 20 gallons). I usually add a bottle each oil change, and yes, it *does* make a difference. Injectors can be partially clogged and your performance goes down so slowly you never notice it until you compare it to really clean injectors. Most folks use the lowest grade gas their vehicle will run decently with, and lower grade gas contains less detergents to help keep injectors clean.

[arkie dem]

15. Chevron Techron is well worth the $.

I use it about twice a year in my 96 Toyota Tacoma.Never had a problem in 7yrs with injectors or anything else. I average around 25MPG combined city and highway driving, strictly highway driving I'm pushing 30MPG.

[CO Liberal]

16. No Chevron Stations in Colorado

We have Conoco, Diamond Shamrock, Phillips 66, and Shell. Plus a few independents and supermarket gas stations.

[arkie dem]

18. You can purchase Chevron Techron at most auto parts

stores. The concentrated costs more, but it's worth it.

Wal-Mart also sells it, just hold your nose and run into the automotive section and grab a bottle and exit as quick as possible. (insert smiley face)

[CO Liberal]

19. I'll Have to Look For It

:-)

[trogdor]

14. They even have 5w20 now.

Newer Hondas use it. I would imagine your engine would have to be engineered pretty damn tight to use something that thin, but the mechanics say it's cool. I think they said any Honda 1998 or newer can use it, but 2001 and newer MUST use it.

[Longhorn]

6. How about synthetic oil?

I was advised to use synthetic oil in my Mustang. I already have to use premium gasoline. I do try to accelerate and decelerate slowly (though there are times when it's fun to take off at the light! ;))

I suppose driving with the top down isn't good for gas mileage, huh? Especially when it's so hot here in Texas that I also run the AC! I have a soft tonneau that I use in the summer when it rarely rains here that covers the back seat and I have a wind guard that fits under the light bar. Do they help with resistance?

Thanks!

[HamstersFromHell]

7. Synthetic oil will help.

I used Mobil-1 myself. I just don't change it as often, since it allows for extended drain intervals as well. I change filter every 3-4k, and oil and filter every 3rd filter change. (9-12k miles)

As for top down vs top up, I'd suspect top down does create additional drag. The tonneau should help. If you're getting wind coming up between the seats it's from the air "curling" into the low pressure area after it goes up the windshield. I know at 70mph raising my headlights on my Miata will produce a very noticable drag.

It varys from car to car...chrysler claimed in their ads once that their convertibles were "windproof" in the cabin at as low as 30mph - mostly due to the extreme windshield rake they use in their "cab forward" design. The better you can cut the air, the less likely it is to "close up" before the rear of the car.

I'd suspect the only way to know in the real world would be to hook a vacuum gauge to the intake and hold a steady speed on a given flat long road with top up and with top down, along with any other variables you might want to try. A lower manifold vacuum reading means you're working the engine harder, so given the same road and speed and weather conditions, that would equal more drag.

Another thing as an afterthought...using cruise control will usually cost you gas mileage, as it tries too hard to keep a set speed, rather than to keep a given manifold vacuum. If you just keep your foot from pressing harder on uphills and let the car slow down a bit as it climbs, you'll save gas over trying to maintain speed.

We had this discussion on the miata owner's list once and holding a steady foot on the pedal vs. maintaining speed can give as much as 3-4mpg more on the highway. (I average 29mpg cruising at 70-75, while one guy tried it on a long trip and averaged 34, with one tank giving him almost 38.)

[Book Lover]

17. Just a quick note

All of my RX-7 manuals strongly declared that you should never use synthetic oil in their engines; of course that is for a rotary where the oil is injected into the combustive mixture. But you should just check to make sure.

[CO Liberal]

8. Can You Change To Synthetic After Using Conventional Oil???

My Chevy has over 60,000 miles on it.

[HamstersFromHell]

9. Sure you can!

I wouldn't advise it if your truck leaks or burns oil, it's too pricey to just pour it through like that.

That said, it won't "fix" any existing engine wear, but it will help slow down future wear.

There was a problem originally with Mobil-1 when it was first introduced with it being so slick it literally got past the seals on older vehicles, but they reformulated it to include a seal conditioning agent to keep seals "swelled" like traditional dinosaur juice does.

[Blue_Tires]

11. a new chip or tune, maybe?