Turbo BMW and 100% GC or 5w-50 mix?

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264
Location
Edmonton, AB
Long time lurker here and couldn't find the info I need, so I decided to join. Excellent forum and information here. I have a 1992 BMW 325is with around 150,000kms that I just recently finished turbocharging and have been debating what oil to use for quite some time now. I've used GC 0w-30 for the past 15 months or so in the car and it seems to be working fine, but I'm not sure how it will hold up with the additional temperatures from the turbo. At bimmerforums.com, everyone seems to think that 100% GC will not provide enough protection, and most suggest I go with a mix of M1 0w-40 and 15w-50. Although that may work, I want to use GC if possible. I need suggestions on either what oil to run, if 100% GC is more than good enough for my application or if I should mix some CS 5w-50 in with the GC? Any suggestions are appreciated. Thanks.
 
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[Welcome!] e36'n, I'm not going to argue with the folks on the Bimmer Forum, but I run straight GC in a twin turbo Audi A6 with zero problems. The car has been sea level to around 11,000' and in sub-zero to 100ºF at high speeds so I don't know what more I can tell you except to say that, unless their is "something about your engine," you should have no problems.
 
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580
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Ontario Canada
[Welcome!] e36'n. If you feel that you need to bump up viscosity, I would mix GC with 5w50 Syntec. The 5w50 is a great oil and I might be thinking of doing the same. I wonder if the elves will mind? [Big Grin]
 
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2KBMW, I've got to tell you...they shocked me on this one; in fact, they do not mind...you know, just when you think you know someone.... [Cheers!]
 

e36'n

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264
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Edmonton, AB
Thanks for the replies. So GC should be more than fine for my application I take it. Does anyone know at what temp it would start shearing or thinning out? Also, would the Castrol 10w-60 that the BMW M3, M5 and M6's run be better than the 5w-50 if I were to mix it? Thanks again.
 

e36'n

Thread starter
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264
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Edmonton, AB
quote:
Originally posted by Auto-Union: I'd use the 5w-50 in summer and GC in winter.
I wasn't under the impression that 5w-50 is that good of an oil though. Isn't it loaded with viscosity modifiers? It's not BMW LL-01 approved either so does that mean it's a base III oil?
 
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489
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Metro Atlanta GA
e36'n, I'm running GC Green 0w30 in my Audi A4 1.8T with no problem. 1.8T's are pretty hard on an oil and GC does not shear in that engine according to posted UOA's. As pscholte said, unless there's something special about the 325i engine like the M3 engine requiring 10w60, as I understand it, or you're going to run a kazillion pounds of boost, I'd think GC would be fine. Also do an UOA with the turbo and the typical driving you plan to do and then decide what oil is best. a_g
 
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489
Location
Metro Atlanta GA
e36'n, M1 0w40 did shear in my 1.8t to a 30 weight so it wasn't any heavier than GC and would provide any better protection. I'm scheduled to do an UOA on GC on my next OCI. I don't expect it to shear in my 1.8t since other UOA's on than engine didn't show it shearing. Since you're autocrossing then I'd do an early UOA and have Terry Dyson do analysis. He's worth every penny. a_g
 
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2,338
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Charlotte Metro area
Castrol web site answered a question I had about mixing with GC. They said it's chemistry was "too different" to mix it with any of their other Syntec oils. That's what the email said: could have been a secretary, could have been a window washer, could have been an engineer, I don't know. FWIW...
 
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I just looked at one of the 02 vintage bottles of the Green and it does not have the usual "Compatible with all synthetic and conventional motor oils," but I did not go to the website to see if those words were found there. As you guys know, the Elfe Meister is not shocked to hear someone say that the Elixer is "different." After all it wasn't developed by humans... [Wink] Vive la différence
 

e36'n

Thread starter
Messages
264
Location
Edmonton, AB
quote:
Originally posted by Titan: Castrol web site answered a question I had about mixing with GC. They said it's chemistry was "too different" to mix it with any of their other Syntec oils. That's what the email said: could have been a secretary, could have been a window washer, could have been an engineer, I don't know. FWIW...
I phoned Castrol yesterday and the woman I spoke with said that they could not recommend an oil (I should follow my manufactures specs) and that they do not advise to mix oil weights under any circumstances. I kept questioning why and she came up with "it's like mixing oil and vinegar." [Roll Eyes] Sure it is... Anyways, I exchanged my 5w-50 for some more GC and that is what I'm going with. 100% GC...oh yeah. If that doesn't work out, I'll try CS 5w-40 or Elf Excellium xll 5w-40 next time. The CS surprisingly meets BMW LL-98, MB 229.3, A3/B3, etc. Can't be that bad.
 
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quote:
Originally posted by e36'n: I kept questioning why and she came up with "it's like mixing oil and vinegar." [Roll Eyes]
Maybe she meant oil and water? Any good purveyor or Euro Elixers should know that oil and vinegar is a fine Euro combo. PS To test her "theory" take two distinctively colored oils of different weights (e.g. GC Green and Syntec 5W-50), mix, shake if you want to, to simulate engine activity, let sit and observe whether or not there is separation of the grades.
 
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