Quote:
Originally Posted by BillionPa
With over 60000 miles of use of both M1 0W40 and GC 0W30 on multiple cars, I can say for sure that Castrol is a better fit for BMW engines. Yes the M1 does shear down to a 30 weight within 2000 miles. That being said, my own analysis shows that GC is actually thicker than M1 0W40 at engine operating temp when both oils are new, by just a little bit.
M1 will re-thicken with time, and at around 7000 miles will be pretty close to a 5W40 oil.
Both are officially approved oils by BMW and meet all warranty requirements, even though GC does not meet 'current specs', meaning API SN.
Nissan V6 engines also run very well with GC, oil analysis had extremely low contaminant numbers even after 8000 miles, whereas the dealer stock oil would be trash after 3000 (Murano with CVT, revs higher for longer than standard trans)
Currently running a 50/50 mix of GC and Redline 5W30 to up the turbo and camshaft protection, it performs very well, and I ran the same mix in my E34.
If you have a dirty engine, 50/50 M1 0W40 and Redline 5W30 plus AutoRX is the magic formula to clean it.
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We're mostly on the same page here (not that you needed my endorsement
).
I have lab results showing M1 0W40 shearing and GC staying more stable, as I suspect you probably do too. I've heard lots of success stories with GC in Nissan VQ35s.
Where I would be careful is mixing GC with ANYTHING. GC has enough esters in it that it can cause some interesting reactions with other oils and
especially with AutoRX. Redline is very high in esters and if you're using ARX I wouldn't touch Redline. Use one or the other, IMO.
I actually had deposits accumulate pretty rapidly when running ARX maintenance dose in GC. At first Frank (of AutoRX) said GC was just fine for maintenance dose. After posting some stuff at BITOG about rapid deposit build up his story changed to more of a 'you didn't say you were using GC! You can't do that!'. At any rate, My theory is that ARX and the esters in GC nullified each other and severely compromised the ability of either GC's original adpack or ARX to do any cleaning. I even observed a weird reaction when I rinsed a measuring cup which contained ARX with GC - the GC surrounded the ARX and made a ball of ARX suspended in the middle of the oil. I haven't seen any oil but GC do that. That was my first clue that I was doing something stupid.
Later I found more horror stories out there of people cooking turbos while running ARX in ester-containing oils etc...etc... Same problem, I suspect.
I wasn't going to get into it in this forum, but: 1/ I support ARX as a cleaner when used properly. The Internet tide has turned against it but it's worked for me. 2/ Redline has lots of esters and cleans quite well on its own without any help. 3/ I won't even attempt to mix GC with anything that might contain esters. I've seen weirdness first hand, and read lots of reports of problems out there.
For BMWs, I like to use TWO bottles of ARX in Rotella T 15W40 or Esso XD3 15W40 (only available in Canada). This seems to clean up VANOS really nice.