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Discussion Starter #1
Hello

I have a 2012 sonata with 148 k miles. The car runs very well but is starting to use some oil, maybe 1 qt per 3000 miles
I took it in for an engine compression test and received the following feedback for each cylinder

Dry. Wet
115 psi. 140 psi
125. 148
120. 145
120. 146

I think these are very good numbers and I will keep the car as opposed to selling it

Question. Is there a diagnostic test available to determine the health of my transmission. I have never had any warning lights and I conducted all of the 120 k mileage preventive maintenance

thanks for any feedback on preventive maintenance going forward
 

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For the turbo model I think the numbers ara ok, for the 2.4 they are a little low. But the short block has a lifetime warranty for the Pistons, rings, crank, and bearings. So if it starts using more than a qt in 1000 miles, or seizes, they will replace it. The transmission, as long as you drain and refill every 50-100 k miles, and see no weirdness, or slipping, you are good to go.
 

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Those numbers sound quite low.
I agree.
And FWIW I don't think there is any difference between the 2.0 & 2.4 cylinder compressions, assuming we're comparing like for like (ie both GDi or MPi)

If I helped you fix it, why not...

Your support is greatly appreciated
 

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The turbo model surely has lower compression than the NA.
Those are low numbers for the turbo and lousy numbers for the non-turbo.
I'm sure the 2.4 has at least 10:1 compression (MPI version is 10.3:1) and I'd expect close to 200 psi in a healthy engine.
 

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IDK the ratio on the 2.0t, but I remember seeing many turbo gasoline vehicles at 7.5:1
 

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The turbo model surely has lower compression than the NA.
Perhaps it does. I've been known to be wrong on occasion.
Regardless, the OP's compression figures are poor. I'm not wrong about that :)

If I helped you fix it, why not...

Your support is greatly appreciated
 

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Those numbers are pretty low so there is definitely some engine wear going on. Good news is they are pretty equal for the most part so the engine should run and idle smoothly and not have much of a drive ability issue, but it is probably down on power.
 

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Interesting to see that the compression doesn't seem to improve much when tested wet. If the rings were worn I would expect the compression to jump right up when a small amount of oil was added to the cylinder.

Hopefully the mechanic doing the testing removed all plugs and opened the throttle fully to allow the best compression to be developed.
 

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Discussion Starter #14
I took it down to the Hyundai Dealer. They will change my PCCV and see what happens. After that they will begin monitoring my oil use. Right now the car used 1 Quart of regular oil (not synthetic) in 1200 miles.
 

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That is bordering on excessive. Another common cause of high oil consumption is valve stem seals. Also a measurement of the intake manifold vacuum can help diagnose ring problems.
 

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I took it down to the Hyundai Dealer. They will change my PCCV and see what happens. After that they will begin monitoring my oil use. Right now the car used 1 Quart of regular oil (not synthetic) in 1200 miles.
I was gonna say something about synthetic oil but you're using regular so I'd stay with that since your engine is old and that I'm sure there's sludge build up. I gonna assume that the seals are worn and needs to be replaced. Maybe the sludge kinda broken up causing a leak cause sludge can plug up. I may obviously be way wrong here tho.

If it's GDI then I'd just keep using it till it begs for mercy cause ain't much you can really do with them since ALL DI engines are known for insane carbon buildup. Of course you could walnut blast it but it's not cheap.

Just trying to help. Also, 148K miles is great to hear. Hopefully you reach 200K. And since certain parts are lifetime warranty, Id get those new parts Installed, Use full synthetic oil after the inside is clean, and just be on your way.
 

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I took it down to the Hyundai Dealer. They will change my PCCV and see what happens. After that they will begin monitoring my oil use. Right now the car used 1 Quart of regular oil (not synthetic) in 1200 miles.
I'd say you'll need to get the oil consumption down to a qt @ 600-700 miles before engine replacement.
Just keep up the maintenance, any oil dino/synthetic, drive the car and don't worry about possibilities.
Just remember, if it ain't broke, don't fix it.
 

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How does the test procedure go for doing that?
Simply fit a vacuum gauge to the intake manifold. Good rings will have between 18 to 21 inches and worn rings will have less. Obviously there are factors like compression ratio and valve timing that influence the reading but you can get a good idea. You can do it with a scantool if you have a map sensor but the figures will be different.
 

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Simply fit a vacuum gauge to the intake manifold. Good rings will have between 18 to 21 inches
Sounds proper old school!
I would imagine by measuring low vacuum you would be measuring a symptom, not the cause. Probably very difficult to really attribute that low vacuum to bad rings, due to low compression with any certainty.

I would be checking compression, maybe leak down, and checking for blow-by rather than pulling out the vacuum guage.
 
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