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      06-10-2017, 09:06 AM   #262
robnitro
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Drives: x5 35d e70 2011
Join Date: Sep 2016
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I saw a video a while back where they tested many brands of synthetic oils in high heat to find the temperature at which they vaporize and start leaving deposits.

Almost every Castrol/ BMW oil did horribly, leaving deposits on the flask and burning at a low temperature.

I would say that this is why they had issues.

For many years on BITOG forums, it's been known that Castrol synthetic is typically a group 3 lower quality base stock. Some weights like 0w40 and 10w60 use a real synthetic base of group 4. Rotella T6 is a group 3+ done by a special process compared to the cheapo group 3's. Mobil 1 tends to use group 4 but that's changing too on some weights.

There is also the factor of the TBN number which fights the harmful acid buildup from water of combustion and the detergency of the oil which suspends solids such as soot.

True diesel oils such as Rotella T6 have a very good TBN and are able to suspend a lot of soot. A lot of the 0w40 oils are good with that too, because of a strict MB standard (229.5).

But the LL04 oils, requiring low ash, were found to be less robust with TBN and soot holding compared to the dedicated oils.

It's just another case to not use LL04 besides the other post I put about vaporization vs ash.
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