I was mystified when I purchased a second-hand Rover 4-stroke mower from the tip shop a while back and found the tank was half full of oil. I really did not think anyone could be so stupid to think a mower can be run on oil alone, but apparently the simple answer is "Yes, people can be that stupid!" The oil was right through the carby choking everything and burnt into a black solid mass all over the plug. No way this engine would have ever started. After I flushed it all out and put in some real fuel, away it went. It was a vintage early 70s Challenger and the base and wheels were in great nick. So I reckon I scored a bargain on that one due to someone else's stupidity.
I have heard of people adding 2-stroke oil to fuel tanks if they intend to store them for a long time. Apparently the 2-stroke oil is very good at keeping tanks clean and preventing rust. Not sure how true this is.
I was going to buy a ride on mower one time and had it all arranged to inspect and pick up. The first thing I noticed when I got there was the whole engine was plastered with oil. This guy was under the impression that modern fuels are no good for 4 stroke Briggs engines because "it all contains Ethanol now", so he was convinced you have to add lots of oil to the fuel to stop engine wear. He was really pouring the oil into it. Of course when he kicked it off I could hardly breathe for smoke fumes. Told him I suddenly wasn't interested and he asked "Why not?". I mentioned I was a bit suspicious of all the oil he was putting in the fuel tank, but he did not have a clue what I was talking about. Evidently he has always mixed oil with his fuel to run all his engines, 2 or 4 stroke. They all get the same fuel. LOL!
