At 11:27 PM 3/9/2011, PB wrote...
>Nothing's wrong with my Westy, but would like to know if STP gas
>treatment will increase mileage and enhance performance.

Techron is widely regarded as the one of the best "in-tank" fuel
injector cleaners. You don't normally use it with every tank (you could
buy Chevron or Texaco gas to get the equivalent of that). A bottle with
a fillup (put the bottle in before filling - helps with mixing) maybe
once a year or two. For really dirty injectors, a double treatment may
help. If that doesn't do it, then it's off to a rebuilder with the
injectors for professional cleaning.

I've used these folks before, with good results:
http://www.cruzinperformance.com/fuelinj.html