Original thread describing the issue here: https://bobistheoilguy.com/forums/threads/boy-did-i-get-taken.348392/
tl:dr is that my recently acquired Scion xB with the known-problematic 2AZ-FE engine was burning a quart of the recommended 5w-20 oil every 300 miles.
In an attempt to remedy the problem I did the following:
1. Did a multi-day piston soak. I drained the oil and left the plug out and the catch pan in place. I then pulled the plugs and distributed a full bottle of Berryman's B-12 Chemtool fuel system cleaner across all four cylinders. I loosely installed the plugs and let it soak for 24 hours. I then removed the plugs, cranked it over a couple of times and poured in a bottle of the SuperTech engine cleaner (Seafoam knockoff) and used a dowel to tap on the pistons a few times to see if a little vibration would loosen them up. Due to a rain shower this soak lasted 48 hours. I then extracted the last remaining bit of fluid with a syringe, installed new plugs and filled it with a mix of leftover oils of various viscosities.
2. I drove it for about 200 miles with a full bottle of Seafoam in the gas tank.
3. I removed and replaced the old filter, then topped it back up with a full bottle of SuperTech engine cleaner and some straight 30 weight. I drove it 100 miles on this oil/solvent mix, then dumped it and refilled with Valvoline full synthetic high mileage 10w-30. The oil was VERY dark for a 300 mile run.
4. I added two ounces of Yamalube Ring Free+ fuel additive to the gas tank.
So essentially I did four different things: piston soak, solvent in the sump, changed oil viscosity, and used a fuel treatment.
Since doing the treatments I have driven 250 miles, about half of which was 70mph highway driving. I am overjoyed to report that the oil level hasn't changed at all! I am absolutely floored by this result--it is FAR better than I expected. My original best hope was that I might be able to reduce consumption to Toyota's stated repair threshold of 1 quart/1000 miles but (fingers crossed) I think I might have even exceeded that.
I'm a bad scientist because I changed multiple variables at once so I din't know which things made the biggest difference. I do know I'm going to continue using the Ring Free until I use up abut half the bottle. I'm going to use the rest of it in my outboard since that's what Yamaha specs it for and if it's as good as they say it might add some meaningful life to my 50hp two stroke by doing what the name implies and freeing the rings.
I'm so happy to be able to report a good result. Thanks to all here who contributed helpful advice along the way.
tl:dr is that my recently acquired Scion xB with the known-problematic 2AZ-FE engine was burning a quart of the recommended 5w-20 oil every 300 miles.
In an attempt to remedy the problem I did the following:
1. Did a multi-day piston soak. I drained the oil and left the plug out and the catch pan in place. I then pulled the plugs and distributed a full bottle of Berryman's B-12 Chemtool fuel system cleaner across all four cylinders. I loosely installed the plugs and let it soak for 24 hours. I then removed the plugs, cranked it over a couple of times and poured in a bottle of the SuperTech engine cleaner (Seafoam knockoff) and used a dowel to tap on the pistons a few times to see if a little vibration would loosen them up. Due to a rain shower this soak lasted 48 hours. I then extracted the last remaining bit of fluid with a syringe, installed new plugs and filled it with a mix of leftover oils of various viscosities.
2. I drove it for about 200 miles with a full bottle of Seafoam in the gas tank.
3. I removed and replaced the old filter, then topped it back up with a full bottle of SuperTech engine cleaner and some straight 30 weight. I drove it 100 miles on this oil/solvent mix, then dumped it and refilled with Valvoline full synthetic high mileage 10w-30. The oil was VERY dark for a 300 mile run.
4. I added two ounces of Yamalube Ring Free+ fuel additive to the gas tank.
So essentially I did four different things: piston soak, solvent in the sump, changed oil viscosity, and used a fuel treatment.
Since doing the treatments I have driven 250 miles, about half of which was 70mph highway driving. I am overjoyed to report that the oil level hasn't changed at all! I am absolutely floored by this result--it is FAR better than I expected. My original best hope was that I might be able to reduce consumption to Toyota's stated repair threshold of 1 quart/1000 miles but (fingers crossed) I think I might have even exceeded that.
I'm a bad scientist because I changed multiple variables at once so I din't know which things made the biggest difference. I do know I'm going to continue using the Ring Free until I use up abut half the bottle. I'm going to use the rest of it in my outboard since that's what Yamaha specs it for and if it's as good as they say it might add some meaningful life to my 50hp two stroke by doing what the name implies and freeing the rings.
I'm so happy to be able to report a good result. Thanks to all here who contributed helpful advice along the way.