for some reason my car is drinking gas. i tried running high test only for a few weeks, but it is barely getting 20mpg, i know i have a v6 and thats not bad...but isnt it supposed to be around 25, especially since most of my driving is on the highway??? i guess im going to buy some new plugs, so which ones should i get? also...should i check air filter, fuel pump, anything esle? and what is a good way to increase gas milage?? thanks.