I use the Castrol synthetic blend, and it seems to work very well. I also just recently used Sea Foam in the crankcase. I poured about a 1/4 of the can in the engine and ran it about 2-3 miles, then changed the oil. My motor is running much quiter, and it feels as though it's got just little more pep. If you have some tick in your engine, you might consider a little Sea Foam.

Tim B
99 Rodeo

Tim Barlow
05' Sequoia SR5
98' 4Runner SR5