Hello. New to the board. Earlier tonight I did a oil change with the Amsoil 5w30 oil. My car is a Ford Probe 2.0 4 cyl. It now has 148,000 miles on it. I don't know what kind of oil the previous owner used, conventenial or synthetic. I keep hearing about switching to synthetic on high mileage cars is not good. My engine is mechanically fine, no oil leaks. So since its bad to switch to synthetic, I still decided to give it a try. Was it a bad idea? I drove it around alittle tonite, I did notice a difference. The car runs more smoother. I'm alittle concern at the moment though, because of what I mentioned above. Any comments or advice would be great, thanks.