I agree with everyone saying don't put yourself in a position of responsibility if something goes wrong... but I'd still help the guy if he's a neighbor and friend. Start out by telling him right off the bat how deadly serious a low oil pressure condition is- that the engine may ALREADY be destroyed. Then help him figure out if its a false warning or a real problem. Put a real gauge on it, replace the sending unit if necessary, etc. but don't get into the guts of the engine and make sure he KNOWS you're just looking at the indicators, not the actual engine.
If its a real problem, tell him that he needs to get it to a professional. Don't offer to help him try home remedies or anything like that.
I miss the days when if a neighbor had a car problem, you could go over and help out, including helping him winch the destroyed engine out and put a new one in if it came to that, all without ever considering "liability." :-/ A cousin of mine was helping a neighbor once, and the battery popped spraying acid all around. No one was seriously hurt, though my cousin did make a trip to the minor emergency center to get his eyes checked and thoroughly flushed. The neighbor apologized profusely, but my cousin just said, "aw, stuff like that happens." And everybody KNEW that you take a certain risk whenever you opened the hood, but it was just part of life. Now its like opening the hood is breaking some "do not tamper" seal. I hate that attitude.
