These might be Mike Miller questions, but here goes: I have a friend who changed out the factory oil in his 335i for Royal Purple synthetic. He said the oil temp went down 10 degrees on average. 1. Has anyone seen a similar result by using the Castrol 10W60? 2. Has anyone seen a similar result using another brand of synthetic? 3. Is there any problem/risk using Royal Purple (or any other non-BMW approved synthetic oil)? Thanks
The real question when it comes to using non-BMW approved oil is whether the oil choice will perform as needed based on service life, driving habits, etc. and the only way to know that definitively is to have an oil analysis performed. Otherwise, you will get plenty of conjecture and opinion. Approved oils are intended to hold up for the 15k mile oil change intervals per BMW's recommended maintenance so at a minimum, that would be your performance target. I suspect most CCA members would recommend more frequent change intervals as does Mike. Regarding oil temp, how is he measuring that? If that was truly a supportable benefit with RP, I'm sure the manufacturer would use it as a claim. I've been running RP in a Yukon for a couple of years but plan to swtich to BMW synthetic at my next change. With my CCA discount, it runs $5/qt at the dealer vs. $8.79 for RP at the autoparts store.
