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I had been using the Castrol TWS 10W-60 Motorsport (and its successors Castrol EDGE 10W-60 Professional and Castrol EDGE 10W-60 FST) for more than 10 years without any (noticeable) problems. For my last oil change the Castrol was not available and as I had read in different threads that it is anyway not the best oil (although it is the recommended one by BMW), I decided to get a new one. I was recommended the Motul 300V 20W60 or the Motul 300V 15W50 and saw that people online were using and having good results with those. I went for the 20W60 and I've had it for a couple of months now.

Last week I got smoke from the car. I stopped and saw that there was oil all over the engine. The car was brought to the garage and they told me that a high pressure line (not sure which part it is) was the problem. I still haven't got the car back but I started thinking if the thicker oil could have caused that. Or is it just the ageing of the car (it's now 15.5 years old)? What do you guys think?
 

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In my opinion it's a line failure and nothing to do with the oil properties. The "cold" side (10W, 15W, 20W) of multi-viscosity oils aren't that much different. The "hot" side (-50, -60) is measured at 100C; at this temperature a 10W-60 and 20W-60 oil will be in the same range of 21.9<26.1 centistokes (cSt). Probably first thing you need to find is where the leak is. The VANOS system pressure is much higher than the engine oil pump pressure.
 

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What broke sounds like the vanos high pressure line to the vanos regulator, they break frequently(based on group of cars not one car). As a guess from posts 1 in 10 have this failure. It is a part I replaced at 200k km just so it did not break.
 

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correlation != causation

The line runs at 100 bar, I'm surprised they don't fail more often. Mine went in January of last year; other than the mess, it's not a big deal.
 
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