Well, heres another long winded answer - sorry, its the way I am sometimes
I 'WAS' using Shell exclusively, but after some problems with fuel pumps and some information from DeathRat about Shell gas in Canada, I decided to stop using Shell. I now buy gas from high volume places, like Speedway and Flying J. Generally I try to buy from truckstops as they have high turnover and fresh gas
I avoid the gas that has 'additives' in it.
I always use Premium gas in both cars, even in my SSE which doesnt require it. It seems to run better in that car.
I wouldnt say I drive gently, but I dont hammer it either. Just normal round town driving, with the occasional Rice Machine and Dodge Intrepid wastings, but thats about it. I do most of my driving on the highway/freeway.
I commute 140 miles a day, and most of it is 2 lane highway speed, with the last 20 miles on Indianapolis Interstates in traffic. But most of the way I am doing between 65 and 75 Mph. Not too much stopping, maybe about 8 sets of traffic signals each way.
Well, my driving sounds similar to yours. We dont have that much weight in our cars, and we dont carry around junk in the trunk. I dont think you bought lemons. I have seen Bonnies that get 30Mpg, and some that get 23Mpg and I cant explain why.
I was just thinking that the last time I got bad economy was when it was really humid and had just rained a lot for a few days. I think I got about 26Mpg on that tank. I was shocked.
Maybe theres a humidity issue that causes economy to drop. Is there a sensor that measures humidity or adjusts the mixture based on air pressure ? Maybe we have a few cars out there that need new sensors or something. That could explain it...
Doesnt California have some different emission guidelines for cars, and maybe different gas formula'* ? Maybe that will affect the economy ?
Anyway, I'd love to hear other thoughts or comments, cos my 97 Supercharged gets way better economy than my 92 SSE, and I would love to fix the old girl to get better gas mileage.