Even with the GM O2 sensor it had when I bought it 18,000 miles ago, its gas mileage was still roughly what it is now...and according to the ECM, there'* nothing wrong.
Normally, I'd expect to see clues like a poor running engine (rough idle/stalls/hard starting/lack of power, etc), black smoke from the tailpipe, error code(*), leaking fuel, dragging brake(*), or other obvious problems, but I haven't seen any of these.
I use the same gas brands (always 91 octane) for both of our supercharged bonnies, so that can't be a factor.
So what do you guys think about why mine doesn't get the gas mileage that yours get?
Any ideas? I'd be soooooo happy to see this car get consistently better gas mileage, especially since I've had to dump so much $$$ into this car since I bought it!
'99 Bonneville SLE, white, 112,000 miles
'02 Park Avenue Ultra, white diamond pearl, 88,000 miles