2005 Prius Piston ring replacement

Time for a new mechanic. Presuming the engine has had a regular diet of "pure synthetic" oil as you suggest, the oil company would be VERY interested in how your engine has worn out that quickly.

More likely is that the valve guide seals have hardened, if the engine has good (normal) compression, then it is not the rings or cylinders that are worn. Is it *possible* that the oil control rings are sticking, sure, but one-in-a-million with synthetic oil; again the oil company would be keen to understand the failure of their product.

 

Sounds like the time for some good old-fashioned testing.

You probably remember from your Bug days, if you do a traditional compression test, and the numbers are low, and you squirt a bit of oil into the cylinders and the numbers improve, that looks more like a ring issue. If the numbers don't improve much, that looks more like valves.

If you use a leakdown tester rather than a traditional compression tester, you can just listen for where you hear the air coming out ... crankcase if rings, intake or exhaust manifold if valves.

If it's just stuck oil rings, say, compression numbers might not look bad. They could be interesting to have, anyway.

Usually, low-mile replacement Prius engines are available cheaply enough to make the labor proposition of rebuilding your old one unattractive.

-Chap

 

How bad is the consumption?

 

welcome!
you took the car to a mechanic, you trust her diagnosis, but you have the capability to replace your own piston rings?

 

yea, I would echo this statement

I'm a very good shade tree mechanic, I'm comfortable doing just about any repair. But I would never touch piston rings. The rule of thumb on a car with 200k miles is you replace the engine with a low mileage junkyard unit you should be able to get for around $500. Go to the dealership and price out a set of rings, and all the gaskets that are going to crumble apart in your hands, and then think about the fact that the rest of your engine is going to be at 225k of wear and tear even after your rebuild.

Frankly, if the oil consumption isn't bothering you, just keep driving it and topping up. The biggest problem with the prius is the auto/CVT design where you can't really get much engine braking to help suck those rings against the bore. If you're intent on replacing the engine try pouring half a quart of marvel mystery oil in and see if that frees the rings or swells the valve guides a bit.

 

Hi Ed
Yeah, I just took in my 2008 Prius for an oil change on 12/20/2023. 233,000 miles and the same thing. Car is consuming oil a lot.
Not sure what it is, but my first guess was also piston rings.

 

Not nearly as much fun doing rings on this car but as others have said not likely they need replacing either. If it was mine I would do a ring soak first, take out all the plugs and put some seafoam or such in for a day or 2. Spin the motor before putting plugs in and see what happens. Then you can do a compression/leakdown. There are many better descriptions of the ring soak process and reasons why here or on the web. These engines have better materials and machining processes than were available in the 60s, if you ran synthetic oit the motor is probably good for over 300K