0W-40 vs a 10W-40 - Will one make turbos smoke more?

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146
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Gatineau QC Canada
To put everyone in perspective car is a BMW 2011 335is, inline 6 3 liter twin turbo (N54 engine). I've always used Castrol Edge 0W-40 Euro Forumla (A3/B4) which is a factory recommendation and the only oil with spec I can find here and I suppose the same before I got last year as well was used. My turbos are currently smoking at decel and will need a rebuild. I am chatting with the vendor of a turbo upgraded internal rebuild kit and he told me the following: Running really low oil weight can cause smoking over time, the factory weight is 5w-30 and I always recommend at least 10w30 because the oil weight can thin out in the summer to wear out the turbos. When you run a 0w30 or 0w40 it will it can thin out so much with heat that it will leak past the oil seals. I then ask him: I asked him well doesn't the W viscosity only means when oil is cold and not at operating temperature. He replies I've had people run 0w30 and 0w40 in those cars and they start blowing oil as soon they start when up. When turbos are protected properly they will last over 100,000 miles.I'm running 15w40 rotella in my BMW 335xi all year round. Ok so with those comments, . Once my 0W-40 oil heats up it's going to act just like a 15w-40 or a 10w-40 right? I'm not the one who misunderstands this? Even though, does he have a point that a 0W-40 could potentially leak past the seals more than a heavier cold weight oil? I understand at operating a 0W-40 vs 15w-40 can have slight differences in the actual viscosity and there is a smaller range of viscosity between it's cold and hot but still... I also live in Canada and drive it in winter which is why I also like 0W-40. Considering the turbo job on this car is a good 10 hour what do you guys have to say, don't want to screw my rebuilt turbos when I'll do the job.
 
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0W when cold will be thicker than 40 when warm. You are right, it will act like a 0 at 0C and like a 40 at 100C. I'd use 0W40 without concern if it meets manufacturer specifications. You could use 0W40 in the winter and use a 5W40 or 10W40 in the summer if that makes you feel better. How many miles did you get on the original turbos? Chances are, you will get similar on the rebuilds. The car is 8-9 years old. Will you have it another 8-9 years? If it were my car, I'd probably keep using XW40 where X changes depending on winter and summer.
 

TheMidnightNarwh

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Originally Posted by javacontour
0W when cold will be thicker than 40 when warm. I'd use 0W40 without concern if it meets manufacturer specifications. You could use 0W40 in the winter and use a 5W40 or 10W40 in the summer if that makes you feel better. How many miles did you get on the original turbos? Chances are, you will get similar on the rebuilds. The car is 8-9 years old. Will you have it another 8-9 years? If it were my car, I'd probably keep using XW40 where X changes depending on winter and summer.
Yeah I rather not change oil with seasons and just stick with one. I have 50 liters sitting at home that I bought on sale lol. Car currently at 75k miles, I can't confirm if original turbos but I would assume they are. I've been running higher boost with a tune, stock is around 9 PSI and my tune makes it around 16 so they take a beating for sure. I don't think I'll have the car for another 8 years no, most likely 5-6 at most
 
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I know this vaping thing is out of hand but now oils smoking?.. what the heck!...‚ Ok..on a serious note. All Xw30's or Xw40's are going to have relatively the same viscosity at operating temp. The W rating has nothing to do with smoking. If anything oil is thicker upon starting and would be less likely to sneak past loose rings and valve seals. Your buddy has it all wrong...
 
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TheMidnightNarwh

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Originally Posted by Mad_Hatter
I know this vaping thing is out of hand but now oils smoking?.. what the heck!...‚ Ok..on a serious note. All Xw30's or Xw40's are going to have relatively the same viscosity at operating temp. The W rating has nothing to do with smoking. If anything oil is thicker upon starting and would be less likely to sneak past loose rings and valve seals. Your buddy has it all wrong...
Oh haha ok let me edit my title ...‚ Thanks for confirming... that's what I figured. Even when cold the oil is gonna be thicker so no way it can past the seal. Another thing I could think of his since the rebuild kit is upgraded it may be specified for the specs he is recommending but I think that's stretching it a bit since the hole in the thrust bearings are mostly all the same size and all.
 
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Ahh, so you have to pay to play. Likely higher boost will increase the rate of wear and chances of oil passing through seals. More frequent rebuilds is likely the cost of admission for more boost. Sounds like you got the car used, so you have no idea how it was previously cared for. I'd say use the oil you plan to use and sleep well at night. Enjoy your boost...
Originally Posted by TheMidnightNarwh
Originally Posted by javacontour
0W when cold will be thicker than 40 when warm. I'd use 0W40 without concern if it meets manufacturer specifications. You could use 0W40 in the winter and use a 5W40 or 10W40 in the summer if that makes you feel better. How many miles did you get on the original turbos? Chances are, you will get similar on the rebuilds. The car is 8-9 years old. Will you have it another 8-9 years? If it were my car, I'd probably keep using XW40 where X changes depending on winter and summer.
Yeah I rather not change oil with seasons and just stick with one. I have 50 liters sitting at home that I bought on sale lol. Car currently at 75k miles, I can't confirm if original turbos but I would assume they are. I've been running higher boost with a tune, stock is around 9 PSI and my tune makes it around 16 so they take a beating for sure. I don't think I'll have the car for another 8 years no, most likely 5-6 at most
 

TheMidnightNarwh

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Originally Posted by javacontour
Ahh, so you have to pay to play. Likely higher boost will increase the rate of wear and chances of oil passing through seals. More frequent rebuilds is likely the cost of admission for more boost. Sounds like you got the car used, so you have no idea how it was previously cared for. I'd say use the oil you plan to use and sleep well at night. Enjoy your boost...
Originally Posted by TheMidnightNarwh
Originally Posted by javacontour
0W when cold will be thicker than 40 when warm. I'd use 0W40 without concern if it meets manufacturer specifications. You could use 0W40 in the winter and use a 5W40 or 10W40 in the summer if that makes you feel better. How many miles did you get on the original turbos? Chances are, you will get similar on the rebuilds. The car is 8-9 years old. Will you have it another 8-9 years? If it were my car, I'd probably keep using XW40 where X changes depending on winter and summer.
Yeah I rather not change oil with seasons and just stick with one. I have 50 liters sitting at home that I bought on sale lol. Car currently at 75k miles, I can't confirm if original turbos but I would assume they are. I've been running higher boost with a tune, stock is around 9 PSI and my tune makes it around 16 so they take a beating for sure. I don't think I'll have the car for another 8 years no, most likely 5-6 at most
I've just did the valve cover gasket and I have the say the valvetrain top looked pretty clean so at least doesn't seem like it sludged. Now if it was tuned or pushed hard when cold that there is no way to know. That is also why going with a upgraded internal rebuild kit should be able to handle better boost for a moderate tune as mine rather. Thanks I will, just hope it won't smoke right away as the guy says hahaha.
 
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Originally Posted by javacontour
0W when cold will be thicker than 40 when warm. You are right, it will act like a 0 at 0C and like a 40 at 100C. I'd use 0W40 without concern if it meets manufacturer specifications. You could use 0W40 in the winter and use a 5W40 or 10W40 in the summer if that makes you feel better. How many miles did you get on the original turbos? Chances are, you will get similar on the rebuilds. The car is 8-9 years old. Will you have it another 8-9 years? If it were my car, I'd probably keep using XW40 where X changes depending on winter and summer.
+1 The viscosity base oil is what contributes most to volatility and burn off.
 
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The N54 was the first DI + Turbo used by BMW and suffered serious fuel dilution as well as carbon build up on the intake valves. IIRC carbon cleaning was recommended every 45k miles (about same time as plugs I believe). There are some early UOA's on this board done by Terry Dyson circa 2007-2009 talking about the fuel dilution. It's one of the few engines I'd recommend a catch can, but with you living in Canada I'd worry about it freezing. If the shop owner has a tuned N54, I'd wonder if the smoke is due to leaky injectors rather than "thin" oil.
 

TheMidnightNarwh

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Originally Posted by BMWTurboDzl
The N54 was the first DI + Turbo used by BMW and suffered serious fuel dilution as well as carbon build up on the intake valves. IIRC carbon cleaning was recommended every 45k miles (about same time as plugs I believe). There are some early UOA's on this board done by Terry Dyson circa 2007-2009 talking about the fuel dilution. It's one of the few engines I'd recommend a catch can, but with you living in Canada I'd worry about it freezing. If the shop owner has a tuned N54, I'd wonder if the smoke is due to leaky injectors rather than "thin" oil.
I personally don't get the point of a catch can if you are still going to walnut blast.Because we agree a can won't avoid 100% of oil gumming up intake valves. I just do walnut blasts every 50k miles-ish. I checked my intake tract and there is a minimal amount of oil film. As for fuel dilution yeah probably but it's not that bad, I've never heard of bad stories happen. I change my oil every 7500KM (around 5k miles). I'm not even sure if it's a shop per say, it's a vendor online. He has videos on different turbo cars, it's Turbo Lab America. But yeah I just don't get his logic. He's like if you don't use 10W-40 instead of 0W-40 your turbos are going to smoke right away.
 
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Hmmm---don't the 0wxx oils have more additives to make the spread? It may be possible that some of these get depleted, resulting in a thinner oil than planned at operating temp. I wouldn't be concerned using a 10w40 or (in summer) even a 15w-40 like the mechanic does. No guarantee it will fix the issue but worth a try.
 
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211,000 on my n54, likely original turbos (I have to think they were warrantied for waste gate rattle but don't see any records of that). Almost always use 0-40 Castrol or 5-40 T6. This design has really strong water cooling and afterrun of the water pump. If it has the high-speed package and its big oil cooler, I wouldn't sweat it much. It will burn maybe a half quart starting at 7000 miles. I don't know why people think these things are so fragile.
 
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TheMidnightNarwh

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Originally Posted by antonmnster
211,000 on my n54, likely original turbos (I have to think they were warrantied for waste gate rattle but don't see any records of that). Almost always use 0-40 Castrol or 5-40 T6. This design has really strong water cooling and afterrun of the water pump. If it has the high-speed package and its big oil cooler, I wouldn't sweat it much. It will burn maybe a half quart starting at 7000 miles. I don't know why people think these things are so fragile.
I just don't want to do all this labor to still get oil smoke and smell in my exhaust. But yeah doesn't make sense to me why the 10W-40 wouldn't smoke compared to a 0W-40.
 

TheMidnightNarwh

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Originally Posted by JLTD
Hmmm---don't the 0wxx oils have more additives to make the spread? It may be possible that some of these get depleted, resulting in a thinner oil than planned at operating temp. I wouldn't be concerned using a 10w40 or (in summer) even a 15w-40 like the mechanic does. No guarantee it will fix the issue but worth a try.
I rather always only use 0W40. I'm not interested in getting 10w40 or 15w40.
 
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