I have a 2000 Toyota corolla with about 170,000 miles and it is using about one quart of oil every 500 miles. The last couple places I took it to said the compression was bad in the number 4 cylinder. Another place said it was a leaking head gasket. Which is most likely, and is it worth getting it repaired given its age and mileage? What would these kind of repairs cost?
You paid for 2 compression tests and didnāt ask for a repair estimate? A leaking head gasket affects compression. You have to ask for estimates in your area.
If the oil loss has been coming on gradually you probably have worn rings. You need a wet and dry compression test on the 3 good cylinders to tell. If you need rings, it is nor worth fixing.
The oil rings clog up with carbon in those engines, doubtful the rings are worn but you will get new rings with the new pistons.
It is up to you if you wish to spend 3,000 to 4,000 on your car.
I didnāt mean āhead gasketā I meant to say āvalve cover gasketā
Is it using oil and leaking oil at the same time? Only you can decide if the vehicle is worth the amount of money it will take plus what else might be wrong.
The valve cover gaskets on all engines ātake a setā when they get old and they lose their ability to restrain oil under pressure, even the modest pressure from the crankcase 9which is openly connected to the space under the valvecover). And PCV valves can get gummed up. Iād try changing the PCV valve and the valvecover gasket. Both are inexpensive on this engine. I just did both on a 2002 Corolla. Both can be done in under an hour (5 minutes for the PCV valve and 55 minutes for the gasket). I think I paid $25 each for the gasket and PCV valve.
Iād be surprised to find and 16 year old daily driver without at least one cylinder below compression spec. If youāre happy with its operation, I suggest just monitoring the oil and keepinā on keepinā on. Once you open up an old engine and start pullinā pistons, youāre in for a rebuild, and IMHO it isnāt worth the price on a daily driver thatās still serving you well.
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Iād do the gasket and PCV valve, like TSMB suggests, see if that helps. If not, I might try an oil additive that claims to free stuck rings. Iām not usually a fan of them, but in this case it might help, at little cost and risk.
Anyone have a favorite oil additive for this situation?
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I have no favorite additives, and donāt usually recommend additives, but I agree with Texases on this suggestion.
Thereās an old axiom that I like:
ākeep a new car running like new; but just keep an old car runningā.
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Iād look for oil on surfaces that are in the same plane as the front of the engine. Looking at the front of your engine which faces the passenger side front wheel, look to each side of the front of the engine and see if there is a ring of oil. If there is, you need a new front seal.
Marvel Mystery Oil. A buddy with an RX7 swears by it to unstick apex seals.
Google ācorolla piston soakā.
+1
I was able to reduce the rate of oil consumption on my friendās Rav-4 from 1 qt every 800 miles to 1 qt every 3k miles by simply changing the PCV valve.
With the exception of some of the light bulbs, I canāt think of any car parts that are cheaper than a PCV valve, so even if changing the PCV doesnāt help, the expenditure of money was very minor.
I have a Corolla, 20+ year vintage, 200 K miles, and have had to replace the valve cover gasket several times over the years to stop leaks. In fact it is leaking as I type, just noticed the leak on the ground under the car other day. So time to do that job again it appears. Thatās a common problem and easy enough for a shop to address. And it can result in the engine appearing to use oil, when in fact it isnāt. Just leaking out is all. But it has nothing to do with the engine compression. Before spending $$ to replace the valve cover gasket, suggest to post the compression readings here to see to what extent compression is a problem on your engine. In the meantime make sure to check the oil level on the dipstick frequently, and top off as needed.
True. It was not my intent to suggest that the oil seepage and the compression problem were directly related. They are only in the secondary sense that greater blowby creates more pressure in the crankcase and thus under the valve cover.