Bonneville Gxp Fuel Mileage

[CMNTMXR57]

The gxp actually uses the same PCM part # as some caddy's of the same year model (can't remember which one offhand) so I don't think it's the tune.

Also, I drove mine to Colorado in the mountains, and got the highest mileage I'd seen with this car by far - 27 mpg. I couldn't tell you why but it was nice.

FYI, never count on GM's tuning being spot on. There are tolerances that allow the PCM to adapt to the vehicle it's in, conditions driven in, etc, etc.

You and I could take our stock tuned GXP PCM's, pull out all the mapping tables, and I bet there are some level of variance. So I would imagine between years, as GM added on more OBDII capabities, self testing mechanisms, and other provisions in the PCM tunes, there can also be a difference despite having an identical part#.

[SAMzGXP]

just cause they have same part number i dont see why they should have the same stock tune

[GXPete]

I was concerned when I first got this Bonneville (my first with the N*), as I was averaging about 9 mpg around town the first couple days. But once I got it 'on the open road' I was pleasantly surprised. I'm getting 25 on the highway and averaging about 20 overall during the work week. I have a 17 mile commute for which I usually take a US route rather than the interstate. It's certainly no worse than the GP GXP I had prior.

[Bigerik]

My numbers seem to be falling right in line with everyone else's. Not a car to buy if fuel economy is a priority.

I sure get the feeling that with a sharp tune, this thing would give both better mileage and more power. Oh well.

[Kersh]

It will be interesting to see what the new PCM for the GXP will do to the gas mileage. (And HP/TQ!!!)