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Which 5W40 oil to buy?
ROH ECHT:
--- Quote from: OllieVRS on April 11, 2023, 08:13:55 pm ---If if I were doing more track days I would definitely look into an oil cooler, good suggestion. Doubt I'll have the confidence to go back though after yesterday :grin:
But speaking of oil coolers, what are the symptoms of one failing?
@ROH ECHT you seem to know a lot about oils. Running my Miller's for 3100 miles resulted in a loss of 0.7L, the best oil consumption my car's ever had during my ownership. Are you suggesting it may have been even better in reality, since 0.25 to 0.65 evaporates anyway?
Thanks :happy2:
--- End quote ---
Well, I think those rates of loss at 5-13% per 5L, can only be accurate if no other means of loss factors in. So a 0.7L loss is 14% suggests the Miller's is either at the higher end of that '5-13% loss-rate' of today's oils, or there is another means of loss caused by your engine. You just won't know unless the Miller's was first tested for evap loss. That is to say, hypothetically, if the Miller's you used was tested and known to have a 6% evap loss, you would know the other 8% was due to something else.
But everyone can expect to see a loss of between 0.25L to 0.65L from modern oils of today. Anything greater would suggest there's more going on to cause their loss.
pudding:
I would personally consider 0.65L to be a huge and unreasonable loss to evaporation.
I think people watch Project Farm boiling his oil samples on a stove and think that is representative of an engine, which of course it isn't. His vapours are flashing off to atmosphere, which is not what happens in an engine with a particularly well designed and sealed PCV system like the EA113's. Most of the vapours are trapped by the crankcase and the rest is caught by the primary oil separator, and fed back into the sump.
When choosing an oil, look at it's 'Flashpoint' specification. The higher the number, the better in terms of boiling off. Ester base oils are generally the best for that, and mineral oils being the worst.
If an engine isn't leaking it's oil, then it can only be going one way - down the exhaust via the combustion chambers, or weeping past worn out turbo seals.
ROH ECHT:
Just to clarify; I didn't come up with percentages of evaporation from Project Farm. I believe the one test Project Farm did (and I shared), he said was to resemble temps at near the piston face and rings.
The range I gathered is from information, I could find, shared by oil companies when searching this a short time ago. They did mention the same, in that oils with mineral oil evaporate at a higher rate.
pudding:
Yeah fair enough, I wasn't pointing the finger at you specifically :happy2:
From my own research, which to be fair wasn't exhaustive by any means, was that these stupid efficiency/pumping losses driven 0W20 oils evaporate the most. A decent quality 5W40 should resist evap' pretty well, especially ester oils as they were designed to lubricate jet engines originally, so can handle a decent amount of heat. Pretty much why top racing engines tend to use Motul 300V :smiley:
Some engines just blow through oil more than others, but it depends on the conditions. Low revving diesels barely use anything at all between changes, especially modern ones with DPF ash build ups to consider, but high revving BMW M and VTEC engines can absolutely chew through it on track days. Probably why BMW specify 10W60 :grin:
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