This may be a stupid question but I have been searching for hours. Is there any reason that I should not use Mobil1 "high Mileage" 10w30 in my 2.4l Turbocharged motor? The car gets beat on every so often, but not for extended periods of time all at once. I moniter oil pressure and oil temps, so when temps get high, I take it easy. From my searching, it seams like a GF-4 oil is a good choice for high temp applications, but I am trying to slow or stop a leak. I thought the leak was from my oil pan gasket, which I think part of the seepage was, so I changed the gasket. Now I noticed that the leak is coming from higher up, maybe the crank seal. The leak itself does not leave a drip on the driveway, but it is being blown around underneith the motor and making a mess. Either way, will this oil hold up to the beating a may induce on it? during my searching, I found this link. it might be good for people like me that dont know an awful lot about oil. http://www.answers.com/topic/motor-oil-2 one more thing....the motor has seen mostly Amsoil TSO or ASL for the 1st 47000 miles with a GC OCI in the middle somewhere. I tried RTS 5w40 SM for the last 3k miles, and the car is deffinetly more sluggish and the leak hasnt slowed, so I want to change to something else.