Originally Posted by reddevil
You cannot use a leakdown tester to test for worn valve guides..
breaking in an engine on synthetic oil sucks.. break in will take a long time and their is a chance rings will not break in on synthetic oil. what was used on the cylinder during assembly is very important to ring break in, you do not want to use synthetic oil.
to check for a warn guide you need to move valve side to side and check free play.
i used to break in all my motors on conventional but Ray from Ray Bates Engineering built this engine and he told me he has switched from breaking in on conventional to using a synthetic (usually Mobil 1 20-50w). he said there was no noticeable benefit at all from using conventional oil during the "break in period"
he said he would disassemble engines that had been broken in on both and the only thing noticeable he said was the Mobil 1 engine was always cleaner and less deposits than the engine broken in on conventional.
remember if we were to be talking about a chevy 350 with a new cam then yes break in oil would be crucial and would def be needed.
to my understanding thats the thing break in oil offers, is more zinc which they have tried to eliminate from all on the shelf brands.
think about it, what was in the engine from the factory? mobil 1 5w-30 synthetic! we all broke our motors in on it. unless someone can show that a different oil is in it for delivery of the vehicle.
but i think if that was the case then there would be alot more strict break in procedure and it would be explained to you before leaving the lot, as conventional oil would never make it one service interval on the cobalt oil life meter takes you anywhere from 7-15k mi before alerting you of a oil change. thats the way i look at it