A friend of mine, who also has a triumph, uses royal purple synthetic oil (20w 50) but uses regular oil and not a motorcycle specific oil. Is that ok? If not, what would it do to harm the engine? If anything. I know nothing about this and am just curious. He told me that his rep (he's a certified mechanic by the way) told him that the royal purple synthetic motorcycle oil is exactly the same, but just packaged differently (as a motorcycle oil) for marketing reasons. Any input?