Horizons Unlimited - The HUBB - Synthetic oils in older bikes

Horizons Unlimited - The HUBB (https://www.horizonsunlimited.com/hubb/)

- Tech (https://www.horizonsunlimited.com/hubb/tech/)

- - Synthetic oils in older bikes (https://www.horizonsunlimited.com/hubb/tech/synthetic-oils-in-older-bikes-42793)

Quote:

Originally Posted by oldbmw (Post 256646)

It may not make sense, but it happens far too often to be ignored. BMW rear engine seals are particularly prone to this senseless event.

It could be PAO Synthetic as this tends to shrink seals. Some of the higher end companies like Silkolene and Motul add Esters to the PAO as they swell seals which negates the effect.

Cheers

Quote:

Originally Posted by oilman (Post 256642)

These days most oils mix but mixing a quality synthetic with a mineral oil is sort of defeating the object of putting the better one in.

Thanks for the answer.

Re above. I was not thinking of mixing the two intentionally, but rather, if I did change from mineral to synthetic, and possibly back again at a later date (if supply/finances demand it), some of the oil that was in the engine prior to it being drained, will inevitably mix with the new oil being added.

This is the scenario I was referring to.

Quote:

Originally Posted by Warthog (Post 256674)

It is no problem, what you will have in your engine whichever way you do it will be semi synthetic :)
what you dont want to mix is castrol R or any other veggie oil with mineral or synthetic. Note semi (as in semi synthetic) does not mean half and half.

The way oils are graded can be very misleading. Unlike nearly everything else the grades refer to a maximum that the oil does NOT meet. For instance SG rated oil can have a maximum of 0.12% of zinc. SL 0.10%.
So if you had a 45 gallon barrel of 0.000001% zinc (or none) mineral oil, you could put a drip or two of synthetic in the barrel and legally sell it as semi synthetic SG rated oil.
It meets the specification, because it has LESS than 0.12% zinc (zddp).