Getting better gas mileage

[Tom63050]

Ways to get better mileage:

1. air up your tires to 32 PSI or higher. The extra tire wear is more than offset by the gas savings, if you do as many of these steps as possible.

2. a good tune-up, of course--including plug wires

3. advance your ignition, and use higher-octane gas if necessary (10 cents more = about 3 percent these days)

4. use a 40,000-volt coil and gap your plugs wider, for a bigger spark; do a search for the writeup on what coils are reliable

5. remove water pump fan, don't use A/C--both are drags on the motor. Windows up if possible, when on the highway. Below 40 MPH air drag is not a big factor, so for sure windows down when it's hot and you're not on the highway.

6. Most important is how you drive. 55 - 60 on the highway; moderate acceleration & low RPMs; coast down hills (with the motor off on long hills); motor off at stop lights, or better yet when approaching them; avoid braking if you will need to speed up again (longer following distances in traffic).

7. I also have larger diameter tires--Kumho 795 A/S 185/80x13, which are 8% taller than 175/70x13s, on aluminum wheels, which are lighter so require less gas to get them rolling from stop. Taller diameter means lower RPM at highway speeds.

 

With "normal" driving my Loyale 4WD wagon gets 28-29 MPG, with tires at 28 PSI. I have all the mods listed above, and with airing up the tires and driving as in paragraph 6, I got it up to 34.6--on a 4WD vehicle! This is a 20% improvement--turning $3.00/gal gas into $2.40/gal gas, and costs nothing to do.

 

Next I will remove the rear halfshafts and report any improvement, since they create friction in the rear diff and also rotate the front-to-rear driveshaft. It may not be worth the trouble, but I gotta know.

[Nug]

The only problem I have with coasting with the engine off is that you lose power brakes and steering, if equipped. Not to mention you can accidently lock the steering wheel (this is a great sensation).

 

Finally, it's illegal in some areas.

 

BTW the air pressure in my Tacoma's tires are all the way up to 50psi for the same reasons listed above.

[Tom63050]

The only problem I have with coasting with the engine off is that you lose power brakes and steering, if equipped. Not to mention you can accidently lock the steering wheel (this is a great sensation).

 

Finally, it's illegal in some areas.

 

BTW the air pressure in my Tacoma's tires are all the way up to 50psi for the same reasons listed above.

Oh yeah, I forgot to mention that you only turn the key one click left to cut out the ignition. If you turn it any more you will lock the steering wheel.

 

Power steering loss is no problem as long as you are moving, and have normal strength. I barely notice it not being there. I also haven't found loss of power brakes to be a problem either. Shutting off the ignition is done only in city driving, so speeds are lower.

 

As for legality--normally I'm big on being law-abiding, but as long as you're careful there should be no problems. Plus, saving gas is patriotic, good for the environment, and gives the middle digit to Hugo Chavez and his buddies in the Middle East. And we can all put the money saved to better use.

[mikeshoup]

The fuel injected cars shutoff fuel with the throttle closed and engine above a certain speed, or at least really leans it out. This can be verified with an A/F meter. It will drop completely off with the throttle closed. I'd debate the negligibility of shutting ignition off while coasting.

 

Motor off at stop lights, see nothing wrong with that if its a long stop light.

 

+1 on 185/80/13 tires. That's what my T-Wag runs and it helped a lot.

[nipper]

Coasting with the engine off is just down right dangerous. There are three ways to avoid an accident, the big pedal, the little pedal, and the steering wheel. Even if you dont have power steering, you have power brakes. YOu also lost the option of applying power to maintain control of the car. Power is not only for acceleration, but for handling.

 

The engine driven fan has a clutch on it usually. The clutch cuts out at highway speed by either a centrifigal or thermostat. Is a blown head gasket worth the risk?

 

You forgot to to mention two other things, bith have a huge impact.

 

Take all the junk out of the car.

 

Install a vacum gauge. the higher you can keep the needle, the better your gas mileage. Oyt of everything on your list, the three with the largest impact are:

AC Use

Tire Pressure

Your right foot.

 

 

nipper

[P K]

I met Dave Stall (The Car Guy) last month. He said tire pressure should be at 5 psi under the max tire rating cold for best safe mpg, and is the single best improvement. Aerodynamics and excess vehicle weight were next. These of course after ensuring you car is running in top form (plugs and air cleaner a must).

 

Get this > (I'm not endorsing) he said the Turbonator actually works on many vehicles as do magnets on the fuel lines. Go figure. Let's not get in a discussion too much about those, but I thought I'd pass his research/opinion.

 

+1 on the vacuum gauge. r/ PK.

[nipper]

There is always one. I guess all those EPA and consumer reprts tests, along with all those chemists, engineers and physics guys dont really know what they are talking about.

 

 

i just lost all respect for the guy (for which i had almost none to begin with) :-p

 

he also claims cars after 1985 dont need tuneups anymore either.

 

Here is something i found on the net

http://www.safetycenter.navy.mil/MEDIA/seashore/issues/fall06/letterstotheeditor.htm

 

If he is the local expert in the area, no wonder everyone is a mess in souther cal.

 

 

 

 

nipper

[ZRX Doug]

Anyone else hear that thud? I believe "the car guy's'' credibility just fell thru the floor..

[GeneralDisorder]

Ways to get better mileage:

1. air up your tires to 32 PSI or higher. The extra tire wear is more than offset by the gas savings, if you do as many of these steps as possible..

 

True - especially if you buy used tires like me. Most tires will be "ok" to nearly twice their spec'd pressure rating. Be careful though as the reduced contact patch can spell bad times on wet pavement.

 

2. a good tune-up, of course--including plug wires..

 

Plug wires rarely do anything but cost money unless they are actually bad (rare) or poor qulity and arcing (less rare). A good cleaning of the air filter and properly gapped plugs should be about all you need

 

3. advance your ignition, and use higher-octane gas if necessary (10 cents more = about 3 percent these days).

 

I don't, but if you must.... the savings is negligible because while the 3 percent seems low, the savings is equally low and thus rarely works out anything more than a break-even.

 

4. use a 40,000-volt coil and gap your plugs wider, for a bigger spark; do a search for the writeup on what coils are reliable)

 

Again - the original coils are 100% adequate to do the job required of them. You will not save a penny by doing this, and you may end up stuck because of it (and out $40).

 

5. remove water pump fan, don't use A/C--both are drags on the motor. Windows up if possible, when on the highway. Below 40 MPH air drag is not a big factor, so for sure windows down when it's hot and you're not on the highway.

 

Actually that's a misconception - A/C will save you money because the drag of having the windows down will cost you more in mileage than the A/C itself will. Mythbusters had an episode about it - don't take my word for it.....

 

6. Most important is how you drive. 55 - 60 on the highway; moderate acceleration & low RPMs; coast down hills (with the motor off on long hills); motor off at stop lights, or better yet when approaching them; avoid braking if you will need to speed up again (longer following distances in traffic)..

 

I agree on the slow speed but not the rest. For one thing we know for a fact that the SPFI system shuts off all fuel flow under closed throttle coasting conditions so that saves you nothing. Stopping at lights happens quickly enough that it's not a savings because of the ECU's startup parameters in open-loop operation. It uses more fuel to start the engine and it takes time for the ECU to enter closed-loop operation - durring that time it uses more fuel.

 

7. I also have larger diameter tires--Kumho 795 A/S 185/80x13, which are 8% taller than 175/70x13s, on aluminum wheels, which are lighter so require less gas to get them rolling from stop. Taller diameter means lower RPM at highway speeds.

 

This makes very little difference in practice, and while taller tires seem like a good idea, it would be better to have shorter tires and still retain the alloy rims as a smaller diameter means less rolling resistance. a 175/70r13 like the 2WD's came with will generally result in higher fuel econemy. I switched my GF's 2WD 87 coupe over to 185's and saw the mileage drop because of it - it has stock 13" X alloys.

 

With "normal" driving my Loyale 4WD wagon gets 28-29 MPG, with tires at 28 PSI. I have all the mods listed above, and with airing up the tires and driving as in paragraph 6, I got it up to 34.6--on a 4WD vehicle! This is a 20% improvement--turning $3.00/gal gas into $2.40/gal gas, and costs nothing to do..

 

I regularly get 28-29 with my sedan - it's got a Weber carbs and I drive like a bat out of hell. Just slowing down alone will save you 10%. The rest is probably the aired up tires and the tune up.

 

If you really want to save draft a semi - 100ft behind a semi will save you 17%. 10ft will save you 37%

 

Next I will remove the rear halfshafts and report any improvement, since they create friction in the rear diff and also rotate the front-to-rear driveshaft. It may not be worth the trouble, but I gotta know.

 

About every 6 months someone on the board comes along and thinks this is the next great thing in fuel econemy. You will find out like they all have that it does nothing at all. The "friction" of the rear diff is so tiny compared to the wheight of the vehicle as to be virtually unmeasurable. You would be wise to just leave it alone.

 

GD

[dave valiant]

Will eliminating the PCV sytem help fuel economy. I live in a state that does not have emissions testing so it would not be a problem.

[daeron]

One thing that I will say..

 

About a year ago I had a thread asking about the more economical way to coast to a redlight; leave it in gear and engine brake, or pop it inot neutral and just coast. Leaving it in gear is the better way, because as has been said already here, at zero throttle, the SPFI injects zero fuel.

 

Since then I have GREATLY altered my driving habits, based on the in-gear coast to redlights.. and have at the same time, increased my average trip time. If you can do your best to notice a redlight as far down the road as possible, and lose speed sooner than you would think to, then I have found that you can VERY VERY FREQUENTLY wind up not coming to a complete stop at all. If the lane was empty, you can simply gas it through the intersection and get ahead of that prosche that blew by you 2 miles back simply because he stopped, and you never did.

 

I hope my anecdote gets its point across; NOT stopping for redlights is another excellent thing that you can do for fuel economy.

[Nug]

Electric fans are more efficient than thermostatic clutch fans any day of the week.

[cd45]

I have tried most of this. I have a big gap on my plugs, running 8.5mm high output wires, MSD coil, tune up every March, 87 octane gas, new tires, straight wheels, and I still only get 23-24 MPG. I don't care any more, this is the best car I have ever owned, given to me by me brother, in 3 years, I have put about $3K into it. It is one of the most reliable cars ever. I have also dicovered that I enjoy working on it, maintenence was a chore on my other cars, this one is a reason spend time with a friend. MPG is nice but, there is a line that has to drawn, I will NOT worry about milage unless it drops to 20 or less. Just drive and enjoy.

[drsubaru]

if you wanna save on gas, get citroen saxo diesel. thats all.

 

60 MPG, with A\C on.

[mikeshoup]

This makes very little difference in practice, and while taller tires seem like a good idea, it would be better to have shorter tires and still retain the alloy rims as a smaller diameter means less rolling resistance. a 175/70r13 like the 2WD's came with will generally result in higher fuel econemy. I switched my GF's 2WD 87 coupe over to 185's and saw the mileage drop because of it - it has stock 13" X alloys.

I agree... to an extent. My T-Wag back when it still had the 3AT, switching from 175/70/13 tires that were on it to the 185/80/13 that are on it now actually helped. Went from around 18mpg to 22mpg. I needed the gearing at highway speeds more than anything with the 3AT.

 

Now that I have the 4spd though, it may be different.

[Bucky92]

My little FWD Loyale gets good enough gas mileage for me...gets as good if not better then most of the hybrids...and at the same time has super low emmissions.. Basically ..you want good gas mileage out of your older subaru...go with a 5 spd FWD and keep it tuned...we carry a good bit less weight..have a slightly different gear ratio ( I believe I read somewhere) and are still perfectly good in the snow with snow treads on....This is my main reason for keeping and loving my Loyale.. put $20 in this and my XT6 when they were both around empty.( $3.27 a gallon at the time) got 165 miles out of the XT6 and got 218 out of the Loyale..and I drive alot of stop and go so thats not all too bad..might put and electric fan in the Loyale someday but for now I am fine with what it has

[Manarius]

Actually that's a misconception - A/C will save you money because the drag of having the windows down will cost you more in mileage than the A/C itself will. Mythbusters had an episode about it - don't take my word for it.....

A/C at speeds above 55-ish mph for savings.

 

I agree on the slow speed but not the rest. For one thing we know for a fact that the SPFI system shuts off all fuel flow under closed throttle coasting conditions so that saves you nothing. Stopping at lights happens quickly enough that it's not a savings because of the ECU's startup parameters in open-loop operation. It uses more fuel to start the engine and it takes time for the ECU to enter closed-loop operation - durring that time it uses more fuel.

Maybe that's the way it is on the older cars, but I just tested it on a tank with my 91 Legacy; +2mpg to shut off the car at long lights.

About every 6 months someone on the board comes along and thinks this is the next great thing in fuel econemy. You will find out like they all have that it does nothing at all. The "friction" of the rear diff is so tiny compared to the wheight of the vehicle as to be virtually unmeasurable. You would be wise to just leave it alone.

Agreed. The weight is already there - the friction is negligible.

[nipper]

From an engineering point of view, mythbusters misses the mark on a lot of mechanical engineering points. As the old addage goes, don't beleive everything you see on TV.

 

nipper

[Virrdog]

Plug wires rarely do anything but cost money unless they are actually bad (rare) or poor qulity and arcing (less rare). A good cleaning of the air filter and properly gapped plugs should be about all you need

I'll have to disagree on this point. Quite a few cars still have the original factory spark plug wires, since its the one things owners never think needs to be replaced. Same thing happened with my Legacy, 10+ year old plugs. It made QUITE a difference in power. I didn't know my car could spin its tires with the AWD, until it happened on accident a couple times after replacing the wires.

 

On top of that, when the typical owner of an older car gets parts for it, they cheap out - especially when they see the price of a good set of plug wires. So right there you have a great majority of cars with incredibly old wires or a cheapo set. I've personally seen numerous times where people had old or crappy wires that were making their Subaru run like crap. So I don't know if I would call that rare. And I don't know of anything that handles thousands of volts for hundreds of thousands of cycles that does not eventually start to break down in some way...

 

Lastly, in the tune-up portion, don't forget to change the PCV valve. If that is stuck open/closed it will affect your engine. Most people don't know where it is, not to mention how easy and cheap it is to replace. I'm pretty sure this is what brought my Sport Sedan out of the middle teens into middle twenties for highway driving. Everything else had already been replaced.

[nipper]

I'll have to disagree on this point. Quite a few cars still have the original factory spark plug wires, since its the one things owners never think needs to be replaced. Same thing happened with my Legacy, 10+ year old plugs. It made QUITE a difference in power. I didn't know my car could spin its tires with the AWD, until it happened on accident a couple times after replacing the wires.

 

On top of that, when the typical owner of an older car gets parts for it, they cheap out - especially when they see the price of a good set of plug wires. So right there you have a great majority of cars with incredibly old wires or a cheapo set. I've personally seen numerous times where people had old or crappy wires that were making their Subaru run like crap. So I don't know if I would call that rare. And I don't know of anything that handles thousands of volts for hundreds of thousands of cycles that does not eventually start to break down in some way...

 

Lastly, in the tune-up portion, don't forget to change the PCV valve. If that is stuck open/closed it will affect your engine. Most people don't know where it is, not to mention how easy and cheap it is to replace. I'm pretty sure this is what brought my Sport Sedan out of the middle teens into middle twenties for highway driving. Everything else had already been replaced.

 

 

Agreed. Wires DO go bad quite often with age. Its a very harsh enviorment under the hood. The insulation breaks down. Not only does this mean that the wires are more succeptable to electrical leakage, but they are exposed to heat (electricity' enemy) moisture, induced spark, and increeased internal resistance. They can also get brittle and break.

 

I used to test ignition wires, the cheap ones would break down in less then 100 hours of testing (some as little as 20). The test is 300 hours at 300 degrees F with 100,000 volts. This is about 7 years running time. (it may have been increased due to newer emission laws)

 

Anything that makes for a weaker spark is a detriment to performance, emissions and mileage.

 

Wires is part of the reason that you are seeing more and more coil over plug systems. 4-8 less parts to maintain. Hotter spark over 7 years, no degredation of high voltage to the spark plugs.

 

i disagree with Subarus interval for wires, but after 10 years they should be replaced.

 

nipper

[PonchoCatalina]

*WARNING - Boring math post to follow*

I know this may be a bit of warped logic, but here's the way I look at it: my '91 Loyale 4WD wagon averages 24 MPG according to the new EPA ratings (I haven't figured out what it's really getting, but that figure will work for this discussion). A new Prius gets 46 MPG based on the same rating system. I paid $900 for my Loyale. A 2007 Prius costs $20,419 - $21,171 (invoice) according to MSN Autos. Now let's do the math...at an average of $20,795, the Prius costs $19,895 more than my Loyale. Today, gas is averaging $3.02 a gallon nationwide. So, to drive my Loyale 1000 miles, it costs $125.83. To drive a Prius 1000 miles, it costs $65.65. That means it costs $60.18 more to drive the Subaru 1000 miles. Thus, I would have to drive a new Prius 330,592 miles to break even on fuel costs vs. purchase price.

 

In conclusion, I would rather pay a little extra for gasoline and have 4wd capability in a vehicle I can fix myself WITH NO CAR PAYMENTS than have a new super-fuel-efficient, super-complex gas-electric hybrid that costs me $300-400 month to buy plus comprehensive insurance as long as the bank owns it. When I think about what I'm NOT paying to a finance company for my Loyale, it makes me almost giddy enough to drive rather than coast down hills, and enjoy a little A/C on a 100 degree day, even if it costs me three or four cents per mile!

[Manarius]

Don't forget to consider that the Prius' batteries need replaced after like 5 years of use. That can be done to the tune of $8000.

[backwoodsboy]

I would rather pay a little extra for gasoline and have 4wd capability in a vehicle I can fix myself WITH NO CAR PAYMENTS than have a new super-fuel-efficient, super-complex gas-electric hybrid that costs me $300-400 month to buy plus comprehensive insurance as long as the bank owns it.

 

 

All I have to say is yes!

[nipper]

Don't forget to consider that the Prius' batteries need replaced after like 5 years of use. That can be done to the tune of $8000.

They seem to have that managed pretty well, its almost ten years in real world testing, and who wants to won a ten year old computer?

 

 

nipper

[Bucky92]

+1000000000000000000 on the comments of the Prius...plus they are Ugly...I will keep my old Subaru any day FWD 4WD ..it doesnt matter they are still a much more versitile car anyway:grin: