No SLE SC in 94.

I've gotten 30-32 mpg in my 99 SE at about 70-75, I haven't yet explored the other end of the speedometer, the Ohio Patrol are very alert here. I find the speed between 70-75 is the best trade-off, you're not going too slow but you're still going faster than half of the traffic while attaining mpg in the high 20 to low 30';*

This past weekend on a 300 mile trip I managed the best MPG'* I've seen since I had my trans rebuilt.
I managed 24.5 MPG, almost 5 MPG above normal. Typically I've been seeing 17-20 mpg with a 60-70% highway and 30-40% in town mix.
But the best I've managed was last July coming back to central Minnesota from Rockford, Illinois (almost made it home on one tank) was 31.5 mpgs in my 95.
In my old 98 SSE non supercharged I managed 35 mpg on my best tank.
The best I've seen a Series II non-supercharged Bonneville do was Smellbirds 1998 SLE which managed an incredible 41 MPG!!! on the way up to Toronto. He'* never duplicated it, but we had a second Bonneville along that got 40 MPG on the same run.
Both vehicles on these runs were doing 75-80 MPH.

What were they drafting?

Michigan air and premium unleaded from BP I believe.

Marty, were those 40mpg estimates a little embellished..even a little? I remember when you guys pulled in to Jim'* house. I was a bit skeptical of it then, especially if at 75-80mph. The way I drive (like a granny...to save gas ) I get 33-34mpg and that'* with a stock restrictive intake and probably a few other things holding it back. I suppose with a hi-flowing CAI and some more tune-up items done I could get more than 34 the way I drive. I'd be more than happy if I got 40

If you can cruise at a speed right around the torque peak rpm of the engine it "should" be the most efficient. All cars vary a little, stock or not, basic shape, air pressure and cross section of the tires etc.., but in theory, the engine is most efficient at it'* torque peak. My old '90 Reatta would regularly deliver in the low 30'* @ 72 mph, which is 2k rpm w/2.97 ratio and 26" tall tires. '91'*, which are the same shape and weight, but run a 3.33 gear and slightly taller tire are usually 3-4 mpg lower at the same speeds.

I got 38 mpg on a 35 mile jaunt on the freeway, cruise set at 60. But it was incredibly boring, so I do 75-80 and get high 20'* low 30'*.

I can't believe your super-fantastic mileage! I thought I'd get best mileage at 55 MPH or so! I am VERY lucky to get 600 KM on a tank of gas, which is perhaps listed at 60 L in the manual but I have added more than 60 at a filling. Should I convert all this to US gallons and miles to help?
> Buick_Engine, can you put your year and trim level in your signature.
Hahahaha, I'm unsure of the trim level! I have the aero-tail at the back, so maybe it'* an SE. It'* a 1997, and the engine is Buick, 3800 Series 2. At what RPM is the peak torque? What is the torque curve like, is it fairly flat from 2000 to 4500 or that sort of thing?
Doesn't it make sense that slower speeds give better gas mileage? That was the reason for the US Gov to make 55 the limit, it was due to the gas crunch, nothing to do with safety.
When I get to 70 MPH the needle goes down a lot faster than at 55 MPH. I know each float & guage is unique but I can also kinda 'feel' it. I also drive without speeding most of the time, if only because I think fuel consumption will be lower.
I am baffled and amazed that anyone would get 35+ at speeds of 65 mph or more.
THANKS
Rob / Buick_Engine