I had a friend crash his GSX600 last year, holed the crankcase, he lost a lot of oil, rode 60 miles to the nearest garage and bought 5 ltrs of car oil (at £9 a ltr!) the bike took 3ltrs to reach the full mark and we then rode 40 miles to Inverness where we bought and applied a liquid metal patch to the hole and bought more car oil to bring it back up to the full mark, it had used all of the 5ltrs of oil bought initially and we hasd ridden briskly. We then rode at high speed back to Stonehaven, over 100 miles - he had no clutch slip at all.
Oil flushed and a new crank case cover and he was good to go (did the same thing to the same side 6 months later by Dunkeld - filled with car oil again etc etc).
So not all car oils cause slip.