In Reply to: oil loss on cruising????? posted by Paul on September 14, 1999 at 14:13:37:
Your car is exhibiting one of the symptoms of a blown head gasket -- but it doesn't come alone. What I'm wondering is, since you don't report leakage onto the ground, have you experienced an unexplained *increase* in your coolant level? This can be due to oil leaking into the coolant system and displacing the water there. How about whitish-looking gunk on the underside of the oil filler cap, on the underside of the water cap (don't remove when car is hot), or on the end of the dipstick? These are all classic signs of a blown head gasket.
Now, why your car only exhibits the oil loss during extended high-speed driving is a bit unusual, but the earlier poster is correct in that the engine is under greater stress (in some areas) when operating at a higher speed and fully up to temp.
One other thought. You could be losing oil past the rings or valve guides at higher speeds (neither is such a great thing...) Have your favorite mechanic put the car onto an dyno emissions tester and see whether your HC goes through the roof (indicating unburnt hydrocarbons -- i.e. oil) when you rev the motor to the rpm's where you're experiencing this problem. If your fuel system is ok, the other place to get high HC is from burning oil, so that might be another indicator of where the problem lies.
Then you can move on to things like compression test, leakdown test, etc... Sorry, I know none of this is such good news.