I have a 1994 Isuzu Trooper. A couple of months ago I had the oil changed at a national franchise place. I heard noises coming from my engine last week. Opened the hood & saw the oil cap had not been replaced. There was oil everywhere. Looked around couldn't find the oil cap. Stopped at car parts places to purchase another oil cap. No one has them. Called the oil place that changed my oil/filter & asked if they had my oil cap. They said no. I told them about the noise my car was making, they said we will come get it by tow truck. I just got a call from the Oil Place who said, we found your cap near the radiator & your car is full of oil, there is no oil on your engine. I asked if they cleaned it & added the oil. They said no. It had oil & there was nothing to clean. They further stated that indeed the car was making noise, but we will have to run a diagnostic. I inquired if it was at their cost and they said no. I said my car was not making noise before, that was due to the oil (at least that is what mechanics told me, mind you they didn't look at my engine). The man got indignant and told me they didn't cause the problem. Now what????? :screwy:
Well either they didn't replace the cap or you have blowby. Without announcing your intention you could front up with someone reputable and take an oil sample for testing. If it shows they have topped up the oil you could argue they are being fraudulent.