Hey, I want to share this case study as a data point for posterity.
~8 months ago, August 2024, I bought a 2010 rav4 with about 250k miles. 4 cylinder, 4WD. It was in generally rough shape. I'll skip the irrelevant bits; he told me that he was losing a quart of oil every 1000-1500 miles and had always kept it topped up. He was using dino oil.
I replaced the valve cover gasket, which did not significantly impact oil loss. There was not indication of any other leaks. I would ordinarily replace the PCV valve too just in case that was a contributing factor, but those are buried on the back of the engine on these cars so I didn't.
At this point, I concluded that most/all of the disappearing oil was burning due to stuck oil control rings. My options: 1. Live with it/defer; 2. Teardown and fix engine; 3. Replace engine with one from junkyard; 4. Try a chemical treatment; revert to option 3 if I accidentally destroy the engine.
I went with option 4. In my research on various forums, I was surprised at how rarely people seem to have tried piston soaks‚ even seriously aggressive piston soaks, before giving up on the engine. What's the worst that could happen? The engine could seize when I start it back up, or I could somewhat damage the cylinders and make the oil burning way worse, or lose compression...so what? You may disagree but that was my attitude going into this experiment.
I read everything I could find on the different active ingredients of interest for dissolving caked-on carbon, and ended up buying a quart of Goof-Off. This was probably the "Pro Strength" but I didn't keep the can.
I removed oil drain bolt and drained the oil, removed oil filter, removed all spark plugs, pushed down a high piston to get all pistons level at mid-stroke, and dumped the whole quart of Goof-Off in, meaning about a cup in each cylinder. (maybe it was a pint can and I put 4 ounces in each, but either way I did not skimp on this step).
I then screwed each spark plug in a couple turns to minimize evaporation, and left it overnight. I placed a clean drain pan underneath the sump to see if I could notice any Goof-Off seeping through overnight (I did not take pictures and don't remember if I saw anything).
The next morning, I siphoned the remaining Goof-Off out of each cylinder, and poured a couple ounces of oil in each cylinder so it wouldn't be starting dry. Some time later I siphoned that out too. I then got ready to start the engine: I installed the spark plugs and coils, added a quart of oil to the oil fill and let it drain out to wash some Goof-Off residue out of the sump; then re-installed oil filter, drain bolt, and filled engine oil.
Then I tried to start it. That was nerve-wracking. My siphoning of the cylinders left quite a bit of moisture, a combination of Goof-Off and oil, on top of each cylinder. It didn't want to start. I didn't think to time it, but I would guess that it took about 2 minutes of cranking (in 10-15 second increments) before it fired up and stalled. One more attempt and it stayed on. For a good 10 minutes afterwards there were huge clouds of white smoke billowing out the exhaust. When that slowed down, I took it for a drive for a few miles. After a couple hundred miles I changed the oil again. After that I used this vehicle like normal for the ensuing ~8 months.
Conclusion: I've put about 3,000 miles on it since then and it hasn't burned a drop of oil, nor have any other problems emerged. I would do this again in a heartbeat. For others considering this type of approach, be prepared—do it at time when you have a different vehicle available as a daily driver, and have a plan for getting a new engine in (or junking the car) if it fails catastrophically. I was absolutely prepared to buy a junkyard engine and install it if necessary.
There were some threads here and elsewhere that I referenced as I planned my approach, but I want to give a particular shoutout to this method, written for prop planes: https://www.savvyaviation.com/wp-content/uploads/savvy_pdf/savvy-oil-control-ring-solvent-flush.pdf
I seriously considered following that method more closely, and using hydrolock to try to force solvent past the rings, but I couldn't bring myself to try it on a first attempt. I would have done it on a 2nd attempt, if my first attempt had not worked and also had not destroyed the engine.
~8 months ago, August 2024, I bought a 2010 rav4 with about 250k miles. 4 cylinder, 4WD. It was in generally rough shape. I'll skip the irrelevant bits; he told me that he was losing a quart of oil every 1000-1500 miles and had always kept it topped up. He was using dino oil.
I replaced the valve cover gasket, which did not significantly impact oil loss. There was not indication of any other leaks. I would ordinarily replace the PCV valve too just in case that was a contributing factor, but those are buried on the back of the engine on these cars so I didn't.
At this point, I concluded that most/all of the disappearing oil was burning due to stuck oil control rings. My options: 1. Live with it/defer; 2. Teardown and fix engine; 3. Replace engine with one from junkyard; 4. Try a chemical treatment; revert to option 3 if I accidentally destroy the engine.
I went with option 4. In my research on various forums, I was surprised at how rarely people seem to have tried piston soaks‚ even seriously aggressive piston soaks, before giving up on the engine. What's the worst that could happen? The engine could seize when I start it back up, or I could somewhat damage the cylinders and make the oil burning way worse, or lose compression...so what? You may disagree but that was my attitude going into this experiment.
I read everything I could find on the different active ingredients of interest for dissolving caked-on carbon, and ended up buying a quart of Goof-Off. This was probably the "Pro Strength" but I didn't keep the can.
I removed oil drain bolt and drained the oil, removed oil filter, removed all spark plugs, pushed down a high piston to get all pistons level at mid-stroke, and dumped the whole quart of Goof-Off in, meaning about a cup in each cylinder. (maybe it was a pint can and I put 4 ounces in each, but either way I did not skimp on this step).
I then screwed each spark plug in a couple turns to minimize evaporation, and left it overnight. I placed a clean drain pan underneath the sump to see if I could notice any Goof-Off seeping through overnight (I did not take pictures and don't remember if I saw anything).
The next morning, I siphoned the remaining Goof-Off out of each cylinder, and poured a couple ounces of oil in each cylinder so it wouldn't be starting dry. Some time later I siphoned that out too. I then got ready to start the engine: I installed the spark plugs and coils, added a quart of oil to the oil fill and let it drain out to wash some Goof-Off residue out of the sump; then re-installed oil filter, drain bolt, and filled engine oil.
Then I tried to start it. That was nerve-wracking. My siphoning of the cylinders left quite a bit of moisture, a combination of Goof-Off and oil, on top of each cylinder. It didn't want to start. I didn't think to time it, but I would guess that it took about 2 minutes of cranking (in 10-15 second increments) before it fired up and stalled. One more attempt and it stayed on. For a good 10 minutes afterwards there were huge clouds of white smoke billowing out the exhaust. When that slowed down, I took it for a drive for a few miles. After a couple hundred miles I changed the oil again. After that I used this vehicle like normal for the ensuing ~8 months.
Conclusion: I've put about 3,000 miles on it since then and it hasn't burned a drop of oil, nor have any other problems emerged. I would do this again in a heartbeat. For others considering this type of approach, be prepared—do it at time when you have a different vehicle available as a daily driver, and have a plan for getting a new engine in (or junking the car) if it fails catastrophically. I was absolutely prepared to buy a junkyard engine and install it if necessary.
There were some threads here and elsewhere that I referenced as I planned my approach, but I want to give a particular shoutout to this method, written for prop planes: https://www.savvyaviation.com/wp-content/uploads/savvy_pdf/savvy-oil-control-ring-solvent-flush.pdf
I seriously considered following that method more closely, and using hydrolock to try to force solvent past the rings, but I couldn't bring myself to try it on a first attempt. I would have done it on a 2nd attempt, if my first attempt had not worked and also had not destroyed the engine.
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2020/01/full-39039-40271-dscn0061.jpg "[Linked Image]")
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2020/01/full-39039-40272-old_sparkie.jpg "[Linked Image]")
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2020/01/full-39039-40273-dscn0064.jpg "[Linked Image]")
