I'm not aiming this question at anyone in particular (I'm really not), but why do so many people get concerned about varnish under the valve cover? Maybe I just havent been inside enough engines yet (a few hundred maybe) to understand why this is truly a problem. I's day 95% of the engines I have been in, had varnish. Some of them, LOTS.
This KA24 engine is the same basic one thats in my 240sx (with minor differences for mine being RWD and this one being FWD). As soon as I got it, it went onto a steady diet of Mobil 1 (I have no idea what the previous owner used).
A year or two later, it started consuming oil. Bad valve seals. Very typical for this engine. Switched to dino for a 3-4 months until I had time to change them. Finally got around to it. Pulled the cover, looked pretty much like the picture in the original post. Fair bit of varnish under the cover, a bit on the cams, tiny specks of sludge here and there. Nothing remarkable. Replaced the seals, drained the dino, back onto Mobil 1.
Couple years later, started consuming oil again. Back onto dino. Found QS 20w-50 on sale at Wal mart, $1 a quart. Bought all they had, a dozen or so. Watered it down with about 15-20% MMO. Went about 3-4 months like this. Pulled the cover, looked pretty much same as it did before. Varnish under the cover, a bit on the cams, maybe a tiny bit less right above the timing chain. Tiny specks of sludge here and there. Nothing remarkable. Replaced the cheapy valve seals I had used, they were hard as rock. Drained the dino/MMO, back onto Mobil 1.
Been on a steady diet of Mobil 1 in various flavors (mostly 0w-40 or HM 10-30), and Rotella 5w-40 ever since. Pulled the valve cover yet again not long ago to investigate a minor leak. Guess what... same varnish, same places, pretty much like it always had, pretty much like the pictures in the original post. Honestly cant really say it looks any different than it ever did, or any different from any KA I have been inside while meandering around the various junkyards around town (and I do that a lot).
My point? If 10+ yearsand over 125000+ miles, probably 90% of it on Mobil 1 (HM and regular) or Rotella, and a few several-month stints of dino spiked with MMO didnt make a dent in the varnish in mine, it probably isnt going to do squat in yours either. One or two oil changes with various high mileage oils isnt going to do it....a few MMO treatments wont do it... why bother. Personally, I dont see a problem.
Just throwing my $0.02 out there.
