Our Toyota has done 160,000 miles and is a US 1993 model with the 5S-FE 2.2L 4cyl. I've read here that the 1997 model + 5S-FE is prone to sludge. Our car smokes on startup, and I thing that's due to seals rather than impeding doom since it's done it for 60K miles or so now. Smog checks are always very clean with the car up to temp. It drives well. The car gets Castrol GTX 10W-30 (started with SJ when new, now SL formulation) every 3,000 to 4,000 miles. It might need 0.5 to 0.8 or so qts between drains, and I attriibute this to the cold startup smoke and a leaking valve cover gasket as well, so no dramatic oil use. My question: I've noticed yellow varnish when I look down the oil filler opening on the valve cover. It's been there forever. Given the mileage and maintenance schedule and low oil use etc., is this cause for worry? Should I leave well enough alone? My guess is that this motor will easily see 200K at this rate -- so I'm inclined to think "why worry?" Did I miss something though? *Should* I worry? Thanks!