I guess this can be a general thread for these situations, if there are enough of them on the forum. I suspect it happens all the time. Here's mine. My car's an '07 Astra 1.4 petrol, on about 50k miles now. It's physically tidy and no major problems other than what I've inadvertently caused. I ran it a fair number of miles (had no choice) with a failed crankshaft position sensor, which seems to have caused further issues down the line: it now has a rattly cam follower, and blew a timing chain prematurely, which I had repaired. It also had a pre-existing oil leak around the head gasket, and oil going into the coolant. See where this is going? If you do a head service/replacement you solve all three problems at once. New cams and followers, new gaskets and seals. This costs about £1k or so. Question is, would it be better to do that or to put the money towards another second-hand car? (Buying new is out of the question, and my budget for a car will never be more than about £2k.) You can't buy a vehicle in as good condition as this for £1k; nor can you buy a significantly better vehicle for £2k. But if I knew what I was doing, perhaps I could save money in the long run by sidegrading into a more reliable £2k vehicle. I don't know.