That is a pretty difficult question to answer considering the large number of brands and product lines in the marketplace. The actual blend percentages are likely to be as varied as the brands and formulations themselves. Most specs are proprietary but you may be able to find approximate percentages by contacting customer support departments of the various producers.
Synthetic is 100% synthetic. There are blends sold that are part synthetic & regular oil. Look for a quart that sates FULL or 100% Synthetic. If it says Synthetic Blend then it is not 100% Synthetic.Synthetic is 100% synthetic. There are blends sold that are part synthetic & regular oil. Look for a quart that sates FULL or 100% Synthetic. If it says Synthetic Blend then it is not 100% Synthetic.
75w80 or 75w90 fully synthetic or if on a budget semisynthetic will do the job just as well
Yes you can. In fact they sell Synthetic blends.
5W/30 synthetic oil is best, conventional petroleum base motor oil is acceptable but inferior, Brand does not matter with full synthetic, but beware, many are blends
No, you must use oils recommended by VW. Blends are verboten.
80/90 semisynthetic hypoid gear oil is what the factory put in it but I use Red Line Heavy ShockProof fully synthetic gear oil. Not cheap but neither was your Harley.
NO, in fact just the opposite is true. Most synthetics are detergent blends. You can however buy a non detergent synthetics.
You can mix part synthetic oil with full synthetic oil.
Semi synthetic or synthetic blend is a combination of synthetic and conventional oil. Full synthetic oil is just that 100% synthetic oil.
It depends on the type of synthetic oil - Synthetic oils based on polyalphaolefin (PAO) / ester blends (e.g. Mobil 1) can be mixed with conventional oil - but you lose the benefit of the synthetic components the more you dilute it. You need to ask yourself why you want to mix it or why you need to use the synthetic oil in the first place - if you're using a synthetic to overcome a mechanical problem (e.g. insufficient heat transfer / oil cooling) then mixing with conventional oil is a waste as you won't fix the problem, same for synthetic gear oils if you are looking for heat transfer out of the drive train - only the "pure" oil will give the best heat transfer response. OTOH, if you are looking for extended oil drain interval, mixing synthetic 50/50 with conventional oil will assist.
Oil that comes out of the ground is not synthetic but is called crude oil. Synthetic oil is man made with synthetic compounds. They are both oil.
Mixing synthetic with semi-cynthetic or even conventional will cause no harm at all. Mixing weight will give you another weight based on the mix. If you mixed 2 quarts of 5w30 with 2 quarts of 10w40 you will theoretically have a weight of 7.5w35.