A few weeks ago I changed the oil pan because someone at the dealership over tightened the drain plug and a few of the threads from the pan were sticking out. When I got the old pan off I noticed the screen was clean but the inside the pan and engine had a thin light brown varnish throughout. The car has 170K miles so I suspect a little varnish is to be expected particularly because the dealership did most of the oil changes with dino oil. I have done 3 changes with Mobil1 and Purolator filters. I have not noticed a change (peering through oil fill cap) in the appearance of the varnish. Should I just continue driving and using the synthetic oil and not worry about the varnish or should I try to clean the engine with a little MMO or Auto RX?
Yes, if it's running alright then that's what I'd do. My personal opinion is that a light varnish doesn't really hurt anything anyway.
You can compare to some of these before/after photos on the Mobil1.com website. But looks like what you are seeing. Sludge Protection | Mobil 1 Cleans with One Oil Change
Yes dino oil burned in residue. In a motor with that much mileage since you already cleaned the sump filter I would not use any additives. Just keep using Mobil 1. Btw, you should check the Variable Valve Timing oil filter too with that much mileage. Its a tiny oil filter that filters the oil that drives the VVT timing cam. The access port to that filter is located under the intake manifold. And requires a hex socket. If interested please check my old posts as I have a good write up on it.
wjtracy- Looking at the mobil 1 pic's the light varnish i was speaking of is more like the after picture...so i guess i'm ok/ thanks all! edthefox5- I will have to look for that one...I'm not afraid to turn a wrench so that one sounds like a rainy day repair.
If you can pull the oil pan the VVT filter will be easy for you. Be aware you need a hex on a socket not a key as the hex bolt is in there so tight I needed a breaker bar to get it out. They really socked it down.
