Lubrication is not about wasting time and money on "ultimate performance" oil, it's about avoiding spending more time and more money on low performance / cheap / crap oil (also known as mineral oil, mixed or not) because of the consequences it may have on your engine.
I don't think that anyone can dispute the logic there. It makes perfect sense for sure
The question has to be asked "When all the mineral oil has been superceded by 'superior' oils, will oil development therefore end ?
It is well known that mineral oil allows a little bit more wear to occur (useful as a running in oil)......but I've just gone to google to find images of 'increased engine wear due to wrong oil' .....and perhaps unsurprisingly there are very few.....there are plenty of colourful graphics from oil companies showing cartoon like situations however.
The 850 *should* use 10W30 or 10W40 oil....but it seems to be generally accepted that 10W40 is 'always fine'
BUT 10W40 has greater viscosity, and in our UK climate that's a bad thing when the weather cools down. Using the wrong oil causes allsorts of things, not least of which the oil pressure bypass valve relieves pressure for a greater mass of oil which should otherwise be performing cooling and lubrication duties. .....and yet more people want to push 'Use the latest and greatest oil' angle, than 'use the correct viscosity'
As I've just witnessed on my mk2 with cold oil and an output shaft seal which has been installed but the seal retaining plate was not yet fitted, the oil pressure behind that seal is huge, enough to blow the seal out. Lower viscosity or warmer oil would not press quite as much.
Which leads me to think about what I've read on TRX forums. Some people report less oil loss when using mineral oil. Mineral oil can thin out and the oil pressure relief valve isn't going to be relieving as much oil back to the sump but instead lets it circulate to provide a higher flow of the essential cooling and lubricating fluid. Critically the pressure behind the output shaft seal will be lowered
The oil seal i removed from the 850 looked in good condition, and this high oil loss has only happened recently while the temperature is below 5 celsius.
EDIT - I don't think there is much oil loss when the oil is cold though, having thought about that some more !
I'm seriously thinking that what i ought to do now when I fit the new seal is, knowing that the temperature is set to drop a lot, switch to 5W30 oil, and therefore keep the pressure behind the output shaft seal a lot lower than now, possibly reducing any oil loss from there.
Edited by fixitsan, 27 November 2016 - 08:34 pm.