i would love to see that on my trip odometer. the farthest i ever pushed it was 425 with the car fully loaded on the freeway (still with the 15 gal mentallity in mind).
i dont know what my secret is either!
im surprised every time i fill up with the mpg i get considering the miles on the engine, 70+ freeway speeds (the Bonny was meant to fly) , the hills around here, the way i drive and from what i hear you guyes on the forum here get. yea i normally average 340-375 miles for every 15 gal i put in so its about 23-25 mpg. but now that i know for sure its a 18 gal tank ill wait till the 400 mark before i start shopping around for gas .
something i learned: calculate the mpg using the big odometer and not the trip odo. my trip broke and took me a awhile to figure out why my mpg calcs were so irradic.
1999-2007: ___1988 Bonneville LE LN3 (Vin C) @ 273,000 miles
and still going strong (<-Faded sun fried grayish ie needs paint)
2007-Present: ___1993 Bonneville SE L27 @ 210,000
Speeding around So Cal (<-Beautiful Forest Green)
Mods: Sylvania Silver Star headlamps. Remote start system with pageing device. K&N air filter. Tranny Cooler. High-flow cat with Magnaflow muffler. Full Class II hitch setup.