My car is a 2009, I've owned it for two years. It was previously a rental car. I've put approximately 3k miles on it each year I've had it and I get the oil changed once a year. It's about due for it again - it's been less than the recommended miles, but it's been a full year since the last one.
I took it in to the dealership for an unrelated problem, and the mechanic told me that he noticed my engine was totally full of sludge because I either don't change the oil enough, or possibly it was like that before I bought it. He told me that I could try to have the engine flushed but he didn't think that would really help, and he said that in his opinion, this sludge was going to cause serious engine problems which would not be covered by my warranty because it was due to lack of maintenance. His advice was to trade the car in - but of course, he works for a car dealership so I didn't necessarily want to take his word for it.
I called my dad (he lives in another state so he can't look at the car) and he said that the mechanic was full of crap. He said that a) You can't tell if there's sludge in the engine without taking the engine apart, and b) It's impossible to build up so much sludge that it would damage the engine if the car is only 3 or 4 years old, even if it wasn't maintained at all before I bought it. He told me to just get the oil changed like normal and forget what that guy said.
So who should I believe?? I don't particularly want to trade the car in (especially if there's nothing really wrong with it and the mechanic was lying), but I don't want to risk my car having some serious mechanical problem that isn't going to be covered by my warranty! Help?