for future readers: oil cooler gasket n oil ring failures, not head gasket, as no coolant in oil pan, engine runs fine. $400+ in parts so far collected new cooler, pipes with o-rings, complete engine gasket set, that was at 60k mi. at time of this writing , still have parts on shelf, still a very minor leak into coolant, after 160k...clean brown stuff out weekly, try to keep rpm under 3500revs, or pressure overtakes coolant pressure n forces drop or three into coolant. some day I'll need to swap out, but until I feel urgency, its keep brown stuff out or turns into thicker sludge. until then watch all rubber hoses, upper, lower radiator hoses, heater hoses, those vent hoses going into reservoir tank. oil will soften n deteriorate rubber over time, I've replaced all once, getting soft again but urgency yet, six months or less, depending on oil absorption over time. so far my problems have spaced themselves out well enough over time cooler hasnt been top list, just in back of mind. checklist of aveo neccesities, timing belt kit w/water pump 100k mi., thermostat 100k mi., check radiator fan for function 100k mi. replace ballast resistor$10 under battery, save money pull DRL's fuse, headlite bulbs $20 at wally world not getting cheaper, deep woods mosquito spray for headlite housings to remove the white road haze accumulation, 40% deet aerosol, $200+ new housings. regular motor oil changes a must 5k-75k...key to getting 400k outta your chevy..