Hello all, I'm Steve. My car is a 2001 Pontiac Grand Prix SE, which has a 3.1 liter engine; not the best place to start for fuel economy, but its better than the 3.8 liter option, I suppose.
Right before I started having problems which led to a crack in the upper intake manifold, I was getting around 22 MPG. I made a number of modifications to it to improve the mileage, I believe most notably some custom bumper extensions which keep a lot of the air from hitting the tire (this modification really helped reduce wind noise at high speed, too) which I crafted out of some extra sheet aluminum.
I've always had an interest in making a vehicle more fuel efficient, but now that my money is tight, I could really benefit from focusing on it.
I've already altered my driving habits to save some gas, and through a combination of that and some power improvements (freeing up intake flow), I've been able to use the automatic transmission's shifting style to save fuel as well (the added power makes it so I don't have to step on the throttle so hard to accelerate at a given rate, and it shifts earlier, keeping my RPM low).
On a different note, I also do web design, and I've combined my interest in that and in cars to create Cars Simplified.
I saw that listed on some car ratings site, but thought it was some kind of typo since it was listed as that on the supercharged 3.8 GTP version, too. Plus, friend has a car with a 3800 (not a Grand Prix) and it's awful on gas (and everything else other than power, really).
From what I read, they have the same transmission, but the final gear is much higher, so it can maintain a lower RPM on the highway.
I've got a GTP and know quite a bit on the cars but I've modded for performance instead of FE. Anyways when I was stock I easily got low 30s on the highway. The GTP has a final gear ratio of 2.9x and the GTs and SEs had something like. 3.2x. IMO the 60* motors are great but a little underpowered for these cars. The 3800 has plenty of low end to get these cars up to speed.