Improving Gas Mileage

[Smith1000]

What are 5-7 things, mechanically, that I could do, in the order of importance, to improve gas mileage?

I have a 2002 PA. I am getting about 22.5 mpg, highway and city combined. This is mostly highway as I drive about 30 miles to work. My old Lesabre used to get about 25 mpg for this type of driving. It has been very cold recently, which may have some impact. I think it it might do better than 22.5 mpg? The terrain is relatively flat. Thanks.

[imidazol97]

Originally Posted by Smith1000

What are 5-7 things, mechanically, that I could do, in the order of importance, to improve gas mileage?

I have a 2002 PA. I am getting about 22.5 mpg, highway and city combined. This is mostly highway as I drive about 30 miles to work. My old Lesabre used to get about 25 mpg for this type of driving. It has been very cold recently, which may have some impact. I think it it might do better than 22.5 mpg? The terrain is relatively flat. Thanks.

You probably are losing the most gasoline through the cold starts. Let the motor idle for part of a minute and then start moving, gently and slowly at first, to get maximum mileage. But the cold transmission and motor oil along with the low coolant temp for a couple minutes will hurt mileage. Using 5W-30 in times when temps won't go above 60 deg. F. for a time is allowed in the owners manual for my 1998 leSabre. The lighter weight equivalent at lower temps for a cold start might help. Long cold warmup times really hurt mileage.

Changing transmission fluid to Dexron VI (if it didn't already have that -- check the manual in glovebox) will make the transmission fluid less viscous at cold temps.

Plugs and wires should be changed by 100K miles.

Drive gently getting into 4th gear as soon as possible for maximum mileage ( when cold the trans won't lockup the torque converter in 4th gear until the coolant temp reaches a certainn level). Getting into 4th gives the highest mileage cruise.

[MagicRat]

^^ Good advice.

Also, it may be time for new oxygen sensors (especially the one upstream of the cat), and new air filter.

Make sure the tires are inflated properly and don't carry unnecessary stuff in the trunk.

Drive with 'hypermiling in mind, including anticipating stops from hundreds of yards away, so you can coast up to them, with a minimum of braking.

Look here for more info: http://www.hypermiling.com/car-mpg.html

[Smith1000]

Thanks. This is great information. I didn't even think about changing the oil and transmission fluid to improve gas mileage. Makes sense though. We have a Sable that calls for 5W-20 oil. I didn't even realize there was a 5w-20 until we go the car. It says to run it year round.

As soon as it warms up some, I'll change the transmission fluid, oil and will do a few of these suggestions.

[ZiggyPA]

Originally Posted by imidazol97

Drive gently getting into 4th gear as soon as possible for maximum mileage ( when cold the trans won't lockup the torque converter in 4th gear until the coolant temp reaches a certainn level). Getting into 4th gives the highest mileage cruise.

I noticed this and thought it was a minor problem with the transmission. But now I know it's a feature, thanks !

[C man]

On my recent fill-up I only averaged 16.6mpg the lowest I've seen in years. Mostly citly traffic, 6 miles one way. Don't know its mostly the cold weather which is colder than usaul for this area (15degrees lows) or my p0341 and p0342 code (cam/crank sensor).I usually average anywhere from 19-21mpg so you seem to be in the average range.

And the magic number for normal functions seems to be 122 degrees. The engine goes into close loop at that tempture. The the heat won't come on until it reaches that temp if you have climate control, the idle stay high until then and the torque convertor doesn't lock up till then. Lower RPMs = slower warm up. Seems that the pcm is designed to make sure the engine gets to close loop as fast as possible. Usaul only takes about 1.5 miles for this to happen even in cold weather from my observations.

[dab1123]

Originally Posted by Smith1000

Thanks. This is great information. I didn't even think about changing the oil and transmission fluid to improve gas mileage. Makes sense though. We have a Sable that calls for 5W-20 oil. I didn't even realize there was a 5w-20 until we go the car. It says to run it year round.

As soon as it warms up some, I'll change the transmission fluid, oil and will do a few of these suggestions.

If you're going to do it, may as well do it right. Flush your Engine w/AMSOIL Engine Flush, then install the correct (see your owners manual) AMSOIL 100% pure Synthetic Motor Oil & AMSOIL Oil Filter. You'll gain between 4% up to 10% (or more) MPG!

[RT Jam]

Originally Posted by ZiggyPA

I noticed this and thought it was a minor problem with the transmission. But now I know it's a feature, thanks !

I'm pretty sure most cars have been doing this for years. I've noticed the same thing on a 94 LHS and a 95 Thunderbird 4.6.

As for 22.5 mixed mileage in the winter. You could still do the mentioned improvements but I wouldn't expect too much gain. 22.5 is pretty good for cold weather mixed in a Park Ave.

I also think LeSabre have in edge in mileage. My Father has a 00 LeSabre. I was impressed with the mileage of that car. So I bought myself a 00 Park Ave. I do not get the numbers he gets.

[bunchacrappyfords]

Where plausible, diving slower improves gas mileage. I'm also a semi truck owner/operator, and though its on a much larger scale (my freightliner holds 300 gallons of fuel), over the course of a trip, i can get about 1600 miles on a tank at 70-75mph and about 1750 miles on a tank at 55mph. That's a HUGE difference considering fuel prices!
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[Smith1000]

I have stopped warming up the car and I am now averaging 25.1 mpg. It seems to do much better out on the highway at about 70 mph. I go about 6 miles on slower (35-40 mph) roads before hitting the highway. For this part of my drive, the mileage is only about 17-21 per the fuel info. Once on the open road, it will read 27-28 mpg.

[Mag00]

Originally Posted by C man

On my recent fill-up I only averaged 16.6mpg the lowest I've seen in years. Mostly citly traffic, 6 miles one way.

Recently I've filed up and had an average of 17.1 - which was the lowest I've seen as well. But it was intense city driving (lots of stop sights and lights). with short-mileage drives as well.

[C man]

Originally Posted by Mag00

Recently I've filed up and had an average of 17.1 - which was the lowest I've seen as well. But it was intense city driving (lots of stop sights and lights). with short-mileage drives as well.

Funny thing, on my last fill-up I averaged 17.1mpg.

This past week,one day we had weather that you could blow the a/c in and the next day we had freezing rain that froze later on that night.

So I drove like "grandpa" in the buick. Down here we can't drive in snow or on ice, its almost like its something from Mars.

[Jrs3800]

Wow... I am gonna go off the wall a little here... This isn't a good example But...

My 1995 Transport has a series III 3800 with the Series II Cable drive Parts... Comp Performance NA Cam, Gasket matching on the heads and lower intake... ZZP stainless PLOG( front exhaust manifold ), Magnaflow High Flow cat and Muffy.. 4T60-E with 3.33 Gears, using a 1997 PCM with 98 Tables... Its not really tuned..

Now keep in mind I am toting about 4000 Lbs with me in the van... 6000 Rpm shift 6200 fuel cutoff... 180F Big Mouth thermostat... Bla Bla Bla..

When we had a cold week here in FL I still pulled down a 17 and was having Thermostat issues, was sticking open too long and sending the PCM back into closed loop... Now with the TPS and Thermostat corrected I am back to 19 Mpg.. In town.. Pretty good for a performance minded 3800 moving a van.. and all of out fuel here is E10, but you guys also get some different blends...

03 Bonneville is doing 21.7 average, cold weather average was 20.0
95 Bonneville is doing 22

But again its an off the wall comparison

[Smith1000]

Out of curiosity, how much is your gas running in your area currently? It is 2.41 to 2.42 around here. There was one place that is 2.49. Seems like the 89 octane is always cheaper than the 87 at the place I gas up.

[C man]

$2.58 in my area. The gas is an E10 blend here also.