Quote:
Originally Posted by GTstunna612
by shearing you mean the actually oil breaking down? Should I stay with GC 0w30 since I change my oil every 3500-4000 miles? What do you use?
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The general term "shearing" refers a reduction in viscosity due to mechanical shearing in the engine, transmission, whatever unit the fluid is used in.
One thing that's important to know is that oil grades (like 30 or 40) are wide bands of measured viscosities. There is a whole range of true viscosity covered by "40", for instance.
GC is a very thick 30, just a couple of fractions off of being a 40 (specs say 12.1 cSt@100C I believe), "40 weight" starts at 12.5. M1 0W40 is a thin 40. It's not right on the edge, but is thinner than most 40s. It's specified as 14.1cSt@100C IIRC.
After 6000km (not miles) in my M52, M1 0W40 was in the high 11s or low 12s as measured by a lab. After 8000-10,000km GC in the same engine is still in the 12s. All of these samples were lab tested. M1's wear protection was just fine, but I like oils which stay at the viscosity they are supposed to be.
Further, I found all of the engines I had around the early 2000s (BMW M52, Acura Integra with the B18A1, Porsche 968 with the Variocam 3.0L) were all noisy on Mobil1 (0W40 in the BMW, 5W30 in the Integra, 15W50 in the Porsche). If you google "Mobil1 noise" you'll get all kinds of stuff. It affects some people, others don't seem to notice. My M52 was so much quieter on
anything that didn't come in an M1 bottle that I switched and am not likely to ever switch back. YMMV. For me the difference in engine noise both idling in the garage and winding it out on the street was unmistakable and dramatic.
Something to keep in mind - dino oils are WAY better than they used to be. Unless you have extreme cold temperatures where you need an oil that's thin in very cold temperatures but still "tough enough" for European specs when up to temp, or you want to run long dealer-style change intervals synthetics aren't truly necessary in most cases. Direct injection engines cause concern as well because in North American tune most of them run rich and contaminate the oil with fuel (basically pouring a solvent into your motor oil). If you're under warranty, don't fool around and just use something that says BMW LL-01 on the bottle (I recommend GC).
My favourite oil in my M52 was Shell Rotella-T 15W40 dino HDEO. Smooth, quiet, cheap, great lab results. I could only run it in the summer, and you couldn't run a full CBS oil change interval but the lab confirmed great results and lots of oil life left changing between 8,000km and 10,000km. Second favourite was Rotella T6 5W40 group III synthetic. That I can run all year round though it's not quiet as smooth and quiet as T.
I'll probably start running Rotella in my N52 this summer (extended warranty expires). Right now I'm running GC.
Some people really like the BMW dealer oil. My dad ran that in his mostly-highway M62TU at half the dealer interval (an extra oil change mid-way between when the car said it needed changing). There were red deposits and staining all over, top end ticking, bottom end knocking, VANOS noises - the thing sounded like a diesel. We did a driveway oil change to GC and on restart 75% of the noises were gone. We had to run a bit of a cleanup regimen but we eliminated the VANOS and all other noises and it purred like a kitten within a few months.