just switched to fully synthetic oil and K&N air filter and picked up about 4mpg. Anyone else have similar experience? '99 Impreza Outback Sport 111k mi

not.. 4, but about 2

l do not think the oil makes that much of a difference, but my family is cars all have a cold-air intake installed. That is, with the exception of my car, but the intake is on my shopping list next paycheck. Enjoy your performance!

l run AMSOIL for all my fluids (oil, tranny, diffs). My increase was about 2 this was a 04 wrx. A friend recieved a 3 mile increase in his 07 Impreza ''i''.

Are u sure this boost in performance did not come from the fact that ur OBS (Outback Sport) needed the maintenance? It is a sincere question. Too often, people attribute big performance gains to aftermarket parts because the baseline was set with worn stock parts.

But to answer ur question, yes, l noticed an improvement when l switched to synthetic & K&N, but only 1 or 2 MPG.

That said, K&N filters r tried & true. They r absolutely superior to the stock paper filter. l am not convinced they flow better than a brand new paper filter, but they maintain this flow longer whereas the paper filter gets choked up quickly. Synthetic oil uses friction modifiers & shock absorbing additives which allows it to be a little ''smoother'' thereby freeing up some power that would have been lost to what is called windage.