Quote:
Originally Posted by Z K
Went out to a track day this past weekend. The air temperature was over 100 degrees. I ran a mix of 6 quarts Mobil 1 0w40 and 3 quarts of Redline 10w60. I had a few quarts of Redline so I mixed it in. The oil had about 3k miles on it prior to the track day.
Car ran fine. It didn't burn any oil. Didn't run any different than TWS on track. Otherwise I don't have anything constructive to add. Planning on changing the oil now as it took quite a beating on that day.
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I'd just tell you to run the M1 0w40 and not bother mixing. If you must mix with M1 0w40 but want to thicken it a bit, try and stay with M1 -- they have a 15w50 with HTHS of 4.5. If you go 50/50 on the 0w40 and 15w50, that would give you HTHS of around 4.1-4.2 (about 10% thinner in operation than what TWS tends to stabilize at).
Otherwise, just run straight Red Line 5w40 or 0w40 (HTHS of 4.4 and 4.0, respectively). There are other options like Renewable Lube 5w40 and Motul 300V 5w40 (HTHS 4.5) too, if BMW certifications are not important to you.
Just remember that you want as thin as possible but as thick as necessary. Thicker = more heat and not necessarily better protection. You need an oil pressure gauge to truly determine if your oil is the right viscosity.