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I have a 1998 Toyota Avalon.

It has 175,000 miles. It sat for almost 5 years. I could see oil gunk around the engine. I cleaned the engine to get a better view of what was happening. There isn't a lot of new oil buildup after driving it maybe 200 miles intermittently.

The engine does not overheat and there is no drop in coolant level. I used a fuel injection system cleaner, topped off the gas tank. Now the stinky blue smoke is worse than ever coming out of the tailpipe and after driving approx 75 miles yesterday, I lost at least a quart of oil.

Aside from an expensive head gasket replacement, what do I need to do?

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Blue smoke means the engine is burning oil. The piston rings are destroyed in a nutshell. Big, long, time-consuming and cash-guzzling repairs are now in your sights. A mere head-gasket replacement will not even touch what is causing the blue smoke. Also, pull your spark plug/coil plugs out off your spark plugs and see if there's any engine oil in the ports. I'd say good luck, but I don't think luck is on your side at the moment.

The car's engine is most likely burning oil due to the piston rings or cylinder walls being severely worn. When a piston moves up and down in the cylinder, the piston has a couple of rings on the side; Two/three seal the explosions of fuel from escaping besides the pistons and smacking the piston into the cylinder walls (sidethrust) and the top ring which is the oil control ring drags oil up the cylinder wall to lubricate the seal rings and then drag it back down again to clean it off from being combusted. When all these rings fail, it allows oil to get into the combustion chamber and become burnt with the fuel.

As a rule of thumb...

Plumes of White Smoke = Coolant except upon cold-start or on particularly cold days.

Plumes of Blue Smoke = Oil getting past compression seal and oil control rings or other oil leaking into the combustion chamber.

Plumes of Black Smoke = Excessive fueling except on very cold days where the engine is automatically chucking tonnes of fuel into the cylinders to aid cold starts.

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    Although my gut also tells me the piston rings are worn/broken, you shouldn't immediately assume that as the unwavering truth. In this case, it could also consume oil via the valve guides or even the turbo, or someplace else. I advice OP to let a pro diagnose it before proceeding. Testing for compression, or taking a look inside the manifold and cylinder may shed some light on this case.
    – Bart
    Jan 26, 2018 at 19:55
  • As to why I said with my little rule of thumb bit at the end that it could be some other oil getting in. A way of testing for piston rings is to sit the car at idle and see if it has blue smoke coming out still. If not, but it has blue smoke whilst the engine is revving, it probably means piston rings. That added with the fuel cleaner used (given we don't know which one) could have reacted with the metal or could have loosened some debris from the injectors causing the pistons to score the cylinder walls, allowing gaps for oil to flow through.
    – yollooool
    Jan 26, 2018 at 20:07
  • Oh, and if the engine is under high load when it puffs out blue smoke, and it puffs out a higher amount when accelerating hard compared to accelerating gently, it will also mean piston rings as the pistons will be under more stress from rapidly-raising RPMs, which will increase blow-by between the piston rings and cylinder walls, allowing yet more into the combustion chamber. This coupled with an older engine tells me this is almost certainly the piston rings, and I'd wager a good amount on it being the piston rings with my experience of working on both diesel, petrol and hybrids of many ages.
    – yollooool
    Jan 26, 2018 at 20:11
  • I agree with you, as said my gut tells me the same, but i'd still advice OP to get a professional diagnose before proceeding since a lot of costs are involved here. BTW, maybe include the explanation in your comments in your answer, they're very likely useful for OP.
    – Bart
    Jan 26, 2018 at 20:30
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Blue smoke from the tailpipe means oil is consumed somewhere in the combustion process. The oil can come from various sources.

If you're technically inclined, i'd take a look in the inlet manifold to check for oil leakage via the valve stems. That's probably the easiest place to check on. If you have a video boroscope, you can take a look inside the cylinder after pulling its spark plug. If the spark plugs are easily accessible, a phone camera might also do. If you can see anything else than a perfectly flat cylinder wall, it's your piston rings. If it looks good, it can still be the piston rings. Due to oil consumption, the pistons will probably have large chunks of black carbon on them. Same goes for the spark plugs.

If you car is turbocharged, oil can leak via the bearings of the turbo on either the inlet or exhaust side. I would suspect that the least though, but it the spark plugs and pistons are cleanish, it might leak via the exhaust side. My bet would be on the piston rings, but it can be something else. I very much doubt replacing the piston rings will be cost effective. (Read: if piston rings are bad, car is totaled.)

You can decide to keep driving the car, but consuming oil at such a ridiculous rate will induce problems quickly. As mentioned, oil consumption will give you carbon deposits. This can get you knock, burned valves, ineffective spark plugs and what not. And lastly, cops may pull you over and give you a ticket.

My advice; i'd let a pro do a diagnostic and make you an offer. If you decide to get it repaired, be aware that additional problems(=costs) may be found during the process. I guess getting a revised engine will be the most cost efficient solution if you want to keep the car, as it will fix all the engine problems, and it'll give your car new life.

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