40mpg Possible in a 98 Buick Lesabre 3.8?

[99LeCouch]

Also, 3/8" thick weatherstripping along the bottom of the hood and grille makes a difference. My engine bay doesn't get as dusty anymore since installing that.

Small individually, large effects when taken together.

[MadisonMPG]

Do those have the 3800 engine in them?
My impala has that engine and I don't get that good gas mileage on the highway.

[99LeCouch]

Yep, 3800 Series II/4T65-E combination.

The W-bodies such as your Impala are capable of getting the same mileage. First thing I'd recommend is deleting the crimp GM put in your Impy's exhaust so it's even diameter the whole length like the H-body, ie LeSabre and Bonneville, exhaust is.

[MadisonMPG]

Get rid of a crimp? Where is it and how do I get rid of it?

[gascort]

Originally Posted by 99LeCouch

Yep, 3800 Series II/4T65-E combination.

The W-bodies such as your Impala are capable of getting the same mileage. First thing I'd recommend is deleting the crimp GM put in your Impy's exhaust so it's even diameter the whole length like the H-body, ie LeSabre and Bonneville, exhaust is.

Interesting; my wife has a W body (98 Intrigue) with the 3.8. She's only gotten as high as 28 mpg with highway only trips, even with my driving. I'm all ears about this crimp in the exhaust from a GM person. I only know Fords.

[99LeCouch]

ZZ Performance

An explanation of the U-bend. Not all 3800-powered cars have this. My LeSabre has a straight exhaust after the cat.

Also, these engines like copper-core plugs changed every 30k miles and hate Bosch O2 sensors. Plus maintaining the transmission every 30k as well.

[MadisonMPG]

How much does it cost to fix?

[99LeCouch]

I don't know, my car doesn't have this. It's likely not much more than a few dollars for a piece of pipe with an O2 bung and a few clamps.

[MadisonMPG]

Originally Posted by 99LeCouch

I don't know, my car doesn't have this. It's likely not much more than a few dollars for a piece of pipe with an O2 bung and a few clamps.

I see, thanks.

[wagonman76]

The Impala might have a sportier final drive ratio like 3.33, which would likely cut into mileage if the 2.84 or 3.06 is sufficient to move the car down the highway.