Posted by Desoto61 [138.162.0.42] on Friday, August 14, 2015 at 09:46:47 :
In Reply to: Re: Re-using motor oil? posted by Paul Cook [76.0.72.230] on Thursday, August 13, 2015 at 15:52:57 :
Another interesting piece of information is that in the US the oil formulations (the GL# or equivalent) are set by the oil manufacturer with input from the auto companies or end users. So one of the reasons the 3000 mile oil change has persisted is that the oil companies have no reason to modify the spec to do so leaving the manufacturer restricted in how long the oil can be used.
This is slowly changing with newer cars, but in Europe where the auto companies define the oil spec long oil change intervals have been the norm for some time.
There are also oils from Mobil 1 and Amsoil that are supposed to be guaranteed for longer change intervals. There may be changes to the additive package but I doubt it's more than marketing.
There are only two reasons I use synthetic engine oils. One is for high performance or turbocharged engines where the oil is worked much harder, the other is to extend the oil change interval. When my HEMI was new I used regular oil at the recommended 3000 mile interval for warranty reasons. Now that the warranty is over I use synthetic but change it half as often. Even then the stuff still looks pretty good.
If you really want to know how good it is you can send some of it off and have an oil analysis done. It will tell you a lot about the engine it came out of and how good the oil is to use in something else. It would be quantitative proof on your idea.