At a service station, a motorist puts the cheapest service station brand oil in a very new Subaru GT turbo ? I couldn't either, but he wasn't interested, his car, his money. The real question is how regularly do you try to help out, and how many success stories have you had ? Three oil sections in supermarkets I've offered advice to obviously confused people, and had thankyous, and they walked off with a good choice. Another time, I saw a guy put 12 litres of oil in his Mitsubishi - he was checking the oil level through the fill cap, not with the dipstick. Apparently this guy had been driving cars since before I was born (well that's what he told me). Looked like the James Bond Lotus with the smoke machine on as he rattled off the driveway.