When I changed the caviler it gained 5% fuel mileage. Now that could occur any number way not starting as quickly. as some one else fix mixture change temp change. Now have you I have seen that kind of change in all the car that i have put sythentic ,but like I said the change has always been under 5%. Which could have occured any number of ways. The only change I really notice is the caviler it did make motor run smoother after use for about 2 oil changes. I am not quite sure when it did that maybe sludge engine and that got cleared. Really they only avantage is the degernt that clean the inside up or keep clean, and it does break as fast. Now if you don't use oil filter rated the mileage you ran beforee oil change you can could have dirty oil that would cause the engine ware. As for the price in mi it about 2.99 -4.29 quart for mobil 1 fully sytnetic. It think the fitler cost about 10-15 more never really checked. Mobil 1 filter is the only one I use

Ok, so that doesn't seem too expensive...to fill my car up with oil for <$25.