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I have a 1989 Beretta GTU 2.8 auto and a 1992 GT 3.1 auto. which is a better gas saver? I feel like the 3.1 saves more gas.

There is not much of a change in power to weight, but the 3.1 has more. There is a small stroke to it and that gives a bit more low end. So at cruise that comes into play. But that is if both engines are in the same shape over all. You could have a 2.8 with better compression that gets better MPG's than a 3.1.
You have two very close engines and both are Multi port injected. Now if you had a 3100 SFI vs a 2.8 the SFI would win hands down. The SFI system is much better because it's not batch fire.

OK thanks. I guess the age and miles of the 2.8 make it waste more gas than it should.

I could be, or they could be the same. Only a compression test on both may shed some light. Hell man it could also come down to which one has better sensors and injectors. Even which engine is cleaner on the valves and combustion chambers. That can be matched by Sea Foam down the brake booster or the cheap way: spray water down the TB when it's running.

All and all I still say the 3.1 would have better MPG's. But that would only be like 2-5 MPG's and that's a guess.
As a side note I have never had a 2.8L. Only a 3.1(90GT) and a 3100(95 Base).

The 3.1 is rated 1 MPG better than the 2.8.

It also may make a difference if you have a 3.18 ratio in both.

Money pit Beretta wrote:As a side note I have never had a 2.8L. Only a 3.1(90GT) and a 3100(95 Base).

Arent you lucky lol.

To me my 3.1 gets way better mileage than the car's original crappy 2.8 ever did.