[lanshark]

I'm trying to get to the bottom of my car's mileage problem... the mileage is 17-19mpg max on the highway, running even 93 octane. I did get 23mpg for a fluke when running 93 *and* fuel system cleaner, but without the fuel system cleaner the mileage drops again.

So far I've done the spark plugs since it has 65k miles, and the transmission flush.