Am curious to see what kind of mileage people are getting with their Bonnevilles...

My city mileage blows - 400km on about 55L. This translates into 13.7 L/100km or 20.55 MPG. (Assuming imperial gallons).

Highway...heh heh. Did a long trip this wknd. 4 ppl in the car, trunk stuffed, wasnt running the air. Last leg of the trip was 388km and filled the tank with 29L of gas at the end. Translates into 7.47 L/100km or 37.8 MPG. Almost 40 MPG - how awesome is that for such an old car with a massive engine.

(For comparison, 2004 GP has 24/40 MPG for the N/A engine and 22/37 MPG for the */C.)

How are you all getting on with mileage? Is my city mileage really low? Should my highway be better (doubtfully...)?

My city mileage is absolute garbage, however i have a few mods that lower fuel effiency and add a bit of power

If I can cruze on the hwy at 100km/h at 1650 RPM, I think thats my best efficieny, again I rarely do that I'm more of a 135-150 hwy driver at 2500 RPM, so the jiuce gets eaten a bit quicker. I usually fill up for gas every 8 days. To be honest, I don't sweat MPGs, when the tank is nearing empty, I refill...oh and my trip clock is wonky so an accrate count never happens :?

That'* really good, my car does about 2000rpm... explanation?

I haven't ever bothered to calcuate fuel economy... I'll just say it'* about what I expect for a car of this size and caliber :P

I don't know where you got those numbers...the '04 GP n/a gets 30mpg highway, and the SC gets 29mpg highway.

But 37.8mpg is pretty good for the car, engine, and the load it had. At 76mph with about 4100lbs. total weight, our GTP averaged 35.2mpg on the way to the track a month or two ago (40miles freeway, 30miles 2-lane, 10miles city), and that was with the AC on. But, it is a fairly new car with an engine that is in top running order, so you would almost expect it to get that mileage.

As for the mileage on your car, it is very good, you aren't going to get much better. You may be able to squeeze another mpg or 2 out of it in the city, but I wouldn't worry about it. That mileage is plenty good. There are a lot of people on here that don't see mileage even close to that.

At 100km/h you should be in the 1600range.. its probably that your torque converter hasnt locked up... just go to 110 then slowlly decend to 100 and it will be locked up at 1600-1700...
I think i was going 12L for 99km I think ive gone as low as 19L for 99km but that was using alot of gas 3.5k rpm last gear locked up. +od... Im going for a long drive today if I get my dash back.. just so I can enjoy it. I think im going to only get 17-19/99km heh

I get around 300km city on a 55L, and around 380km (400km MAX) highway.

It'* probably due to my transmission (I'm blaming that for a lot these days).... she idles too high and revs too high.

ah chit...its gonna be 1 and a half fill ups to drive 8 hrs in October...I dunno Merlin, I'm getting about 100km more on the hwy and in the city.

I'm not sure what I get with just city driving- I do a mix of both. But I usually get around 520-550 KM to a tank of mixed driving. The most I've got on just Highway driving was 620KM. Not bad huh?