I averaged 31 MPG in my STS V8!

[Benjamin Simon]

It can be done. It is really easy and you can start doing this today!

But... there is a caught...

The 31 MPG was on a 8 mile road. Some hills, but no stop and go. I put the shifter in manual. The shifter will allow itself to shift into 5th gear at 35 miles per hour.

Yes, I drove 35 miles per hour for 8 miles. Per the computer, I averaged 31.1 mpg.

The speed limit was 45 on the 2 lane country road. The trip was going great until some mustang GT came flyin up my ass. That bitch tried to pass me, but bored with the slow trip I shifted it back to drive and punched it. By the time her got up to my side mirror, I left him in the dust (while he was still in the passing lane) along with all of the gas I saved.


Nevertheless, if gasoline reaches $10 a gallon in the short term, I can help out and get 31 mpg.

[TobyJohnson11]

I set the cruise the other day in my v8 at 55mph and was getting 30.4 mpg. It is very much worth it if you can stand getting passed by old people. I am getting a K&N soon and will be happy to see it if changes any.

[Benjamin Simon]

Originally Posted by TobyJohnson11

I set the cruise the other day in my v8 at 55mph and was getting 30.4 mpg. It is very much worth it if you can stand getting passed by old people. I am getting a K&N soon and will be happy to see it if changes any.

I only get 27ish mpg going 55. Damn it.

[pjbizjak]

Has anyone taken a long trip via a Turnpike or Interstate in their V8 STS 5/6spd and recorded MPG at different speeds using cruise control? Say 50 miles @ 55MPH, then another 50 miles @ 60MPH and so on? Ignoring weather and head/tail winds sometimes going 60 gets better milage than going 55 based on the cars curb weight and rolling resistance(tires play a big part here), just curious!

[AllWheelEric]

Originally Posted by pjbizjak

Has anyone taken a long trip via a Turnpike or Interstate in their V8 STS 5/6spd and recorded MPG at different speeds using cruise control? Say 50 miles @ 55MPH, then another 50 miles @ 60MPH and so on? Ignoring weather and head/tail winds sometimes going 60 gets better milage than going 55 based on the cars curb weight and rolling resistance(tires play a big part here), just curious!

I am geek enough to have done this. I used a 2-3 mile flat stretch of interstate along my daily commute, using cruise control and the car-computer's average MPG reading.

55 mph 25.4 mpg on 4 runs
60 mph 24.0 mpg on 6 runs
65 mph 24.2 mpg 5 runs
70 mph 21.5 mpg 5 runs
75 mph 19.2 mpg 3 runs

This is on a 5-speed AWD V8.

[pjbizjak]

Based on your findings it looks like MPG drops off quite a bit driving over 65MPH. I have an 07 v8 with 6spd RWD, does anyone have MPG figures based on that?

[STS4-704K]

I picked up an off-lease '05 STS4 a couple of months ago. It has about 43K miles on it with new tires. It's going on its 1st long highway trip (~700 miles) next week. I'll report back on the mileage.

So far my across town 12-mile commute has yielded about 16mpg.

BTW-Thanks to everyone on this forum for all of the good advice on TSBs. Your info helped me to get the tranny reprogrammed, the driver's door handle fixed, and the wiggly seats solidified!! Although I think the tranny will also need the TCC replaced.

Good thing it's CPO and covered to 100K miles!

[ejguillot]

From a previous gen 2000 STS owner, I can see why the V6 STS is so popular these days. That mileage sucks, especially the AWD versions!

My average mileage at various speeds (flat roads, using cruise control, for a 4-5 mile stretch, multiple runs). The 4 speed 4T80E trans will engage 4th gear at about 40, and fully lock up the converter at about 45 (turning 1500 rpm or so).

80 mph: 23-26 mpg AC on, 25-27 mpg AC off.
65 mph: 25-27 mpg AC on, 27-30 mpg AC off.
50 mph: 29-32 mpg AC on, 32-35 mpg AC off.

And of course all of my gen STS's were V8's.

Best mileage I've recorded over a full tank of combined city/highway was 21.8 mpg, and that was with most accelerations gentle enough for the upshifts to happen at 2000-2500 rpm.

[Greg00coupe]

I also had an '00 STS. Bigger car ran faster (my impression) and slightly better gas mileage. What happened? Yes you can stretch gas mileage but at some point the driving becomes unsafe when you don't keep up with traffic. I have a 6 speed Corvette. A few years ago we had a club rally where best gas mileage was the target. I was out in the country with little traffic and got almost 70 MPG. A lot of coasting and getting up in high gear quick. It was interesting but I'd not want to drive that way.

We waste a lot of gas at traffic light and such. Wish there was a way to economically turn off and restart the engine at stops.

[ejguillot]

There is: The mild hybrids that GM is cranking out do exactly that. An oversized alternator and battery pack that can drive most accessories by electricity (power steering, AC, and so on) so that the engine can be stopped while you wait at a traffic light and the AC keeps you cool. Step on the gas and the engine restarts instantly.

GM should find the money to make this standard on every vehicle they sell.
Wish mine had that, city gas mileage sucks on mine as bad as a current gen STS.