With fuel prices climbing and many consumers hitting their own personal limit for the cost of a fill-up - I've now learned not to blink when the pump rolls past $75 while filling up my pickup truck - many are switching from midgrade or premium to regular grades of gasoline. Premium sales have fallen over 5%, according to retailers. This, of course, is a good thing considering the vast majority of all vehicles sold today will work just fine on regular. If you've got any question about it, check your owner's manual, and if it indicates that it's acceptable to run the vehicle on good ol' 87, try out a few tanks and see if it makes economic sense. On the other hand, if you're trying to run 11.7:1 compression on the street, roll right on past the lesser grades and as the numbers on the pump fly by, work on convincing yourself that premium fuel is less expensive than a set of JE forged pistons.