I'm on my 4th vehicle with the 3800 (two L36s and two L67s) and none of them got less than 30mpg on the highway. The RWD L36 was at 35mpg and still on the stock tune (the 96 PCM on the Camaros was unflashable). I could have pushed 40 with a better tune I'm sure.

 

Mine must need some work then, because I can't break 24 mpg. It's always 23.xx mpg.

 

Wow really? I get about 21 or so in town bone stock on my Monte. My L67s did upper teens in town too. Got 32 on the highway the other day. Got 415 miles on my last tank and the last 135 miles of that was all in town and a lot of stop and go cause i have bad luck with red lights in this town. You definitely need to check things over if that's what you're getting on the highway.

 

It's 23.xx all the time, highway or not, that's the weird thing. Usually my cars get slightly better (1-2 mpg maybe?) mileage on the highway. I thought it was normal because it runs so great. 80,000 miles, spark plugs are probably the originals. I can't find a spark plug change in the records anywhere. Occasional P0440 code, but I didn't think that would kill the mileage.

 

When was the last time you changed your fuel filter? I was getting that code before i changed my filter and my gas mileage was not as good as it should have been.... Changed it and that code does not come up and i get awesome gas mileage.

 

My 2004 MC Dale Jr with the L67 engine usually only gets around 25mpg on mostly highway driving and I have fully tuned this engine up, replacing everything ignition related except the ICM and coil packs. Also replaced fuel and air filters as well as pre-cat O2 sensor. On a recent long distance trip to Georgia, I finally got 29mpg on one tank with the rest averaging between 25-27mpg. Last year I took a long distance trip in it to texas and the best I got was 27mpg with most of the tanks at 25mpg and the terrain was a lot flatter than it was in Georgia.

I really think it is the Borla Cat-back I installed earlier in the year that has helped the mpg's because that is the only thing that has been done to the car in between the time of the two long distance trips.

I had heard about it being on Ward's best engine list quite a few years back. My ex-wife and I had also owned a 98 GP GT that we bought new and I was very impressed with the engine in it and is why when I went looking at something else to drive, I looked for cars with this engine in it. My ex-wife got rid of the GP about two years ago with over 200,000 miles on it and it still ran good. It was starting to have some tranny problems though.

My current MC has 97,200 miles on it so it should last many more years. I have already had the Intake manifold gasket repair done with the new aluminum gaskets so that has been done.

Wayne

 

My old Dale Jr that I used to have got great fuel mileage on the highway. I averaged right around 30-31 or so the whole time I owned it. My 98 GTP was the same way. Maybe I just have a knack for it, I don't know.

 

I have bearly put 500 miles on my SS with a supercharged 3800 and i must say I am already impressed love the engien and the car even more I think this will be my first car I will keep over the 2 year mark lol

 

I've not changed it in the year I owned it. Great idea though, for what it costs I am going to try to do that this week. It can't hurt and probably needs done anyway.

 

You never know right, I have a 2000 SS that has 218 500 KM and i swear when i took the old filter off the gas coming out was a brownish colour, not sure if it had ever ben changed lol.I get about 30-33 MPG on the highway