04-08-2008, 02:26 PM
ScottyB Wrote:the difference between a 5 and 10W-30 is thickness when cold. you can get away with a thicker 10W oil in warmer climates during startup.
in your case neither oil would protect better under high heat since they are both 30 weight when at operating temperature. thickness does not necessarily protect better anyway but that is for another thread.
also, you will mostly likely not lose any MPG's until you get into some fairly thick oils like a 10W-40 or 20W-50. some cars are more sensitive than others though.
I really didnt notice any drop when I switched from 10-30 to 15w-40, but then again I switched from Mobil 1 to Royal Purple.