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Why oil loss only at high speeds and distance

My 2002 Toyota Highlander burned up to a quart of oil very 300 miles when on a recent long distance freeway trip. It must be burning it out the back as there is no drip. Clearly, there is a leak, but why only when driving on long freeway trips? Can this be due to pressure build-up and a clogged PCV?

“Can this be due to pressure build-up and a clogged PCV?”

It sure could be.

Engines tend to burn more oil at sustained high speeds and loads because the surface of the cylinder wall gets hotter and the little bit (or more in your case) of oil the rings don’t scrape away gets burned off more readily.

If you do a lot of short trip driving you build up bot water and gasoline in the crankcase which makes you think your car doesn’t burn any oil at all. When you go on a trip you quickly burn off the gas and water. Also, how fast were you going? Were there mountains involved? Towing?

Check the PCV system from end to end, including the vacuum port that feeds it…How many miles on the vehicle?

“Can this be due to pressure build-up and a clogged PCV?”

As the others have already stated, a clogged PCV valve, or a clog in the line leading to the valve, could certainly cause this problem.

But–why wonder? There is probably no maintenance procedure that is cheaper than replacing a PCV valve.

When you buy the valve, you should also buy a can of spray solvent to clean the line. It is very possible that your total cost will be no more than $10. Isn’t it worth investing that small sum in order to remove this problem from your list of possible causes of oil consumption?

6-Cylinder 2002 Highlander ? If That PCV System Overhaul Doesn’t Do The Trick . . .

. . . you should probably consider checking this engine for sludge.

Toyota made several years of vehicles that many people claim were highly susceptible to a build-up of engine sludge. The lists I’ve seen compiled, include that 02 Highlander 6.

Toyota extended the engine warranty on certain models/engines to address customer complaints.

Thanks all. The car has 120k miles and the freeway driving indees was over mountains and at about 70mph. I’ve replaced the PCV valve today and will see what happens. Thanks again.

How long since you have changed the oil?

You need to do more than replace the valve…The hose the new valve plugged into and the vacuum port the other end of the hose connects to must also be cleaned and checked for proper flow. Is your air cleaner box full of oil??

I change the oil every 5k (just changed it) I do not see oil in the air filter box.