Hi,
i recently replaced the oil pan gasket in my 2008 JKU, and noticed a yellow / amber film on all the metal. I cleaned it off of the gasket's mating surface and finished the install, but am wondering what is causing the yellowing?

It looks to be the same color as when you google engine sludge, but there was no actual buildup of anything sludgy. My second guess is that it could be varnsih.

It now has 145k miles on it and in the past 40k that I have owned it, I have used Mobile 1 high mileage with a Fram filter (always seemed fine for me), and replaced every 5k. By running synthetic, it shouldn't be a sludge issue? I do have to add a quart about halfway between oil changes.

I've also heard that the yellow is normal reaction with the aluminium alloy and not a problem.

The engine has always had a slight tick in the upper end, which I have written off as the injectors working.

It runs like a top, but within the past day or two, has sounded a little different, noisier. Time to change oil anyway, hopefully that is all it needs, and am wondering if I should try removing the varnsih.

From some research, the best method is to buy some Pensoil Ultra and do some 1000mi flushes, and then go back to M1.

I also purchased a Wix Xp extended filter (51516) and a pancake adapter to install a real oil pressure gauge.

Is there anything else that I should consider?

 

That yellow could be factory sealant perhaps. Sounds like you are doing the correct things. I would use NAPA Gold or Wix filters - they are the same and very high quality.

Just some trivia - your crankshaft, TC, Tranny, DS and diff pinion have rotated about 300 million times since new. They will wear so if it is good on oil usage and runs well then just change the oil and drive it and enjoy.