I’m considering doing a fast flush on a 2005 Subaru 2.5L non-turbo boxer engine. The oil consumption has gotten pretty bad and I have reason to believe the oil rings could be sludged and or the piston oil ring return holes are plugged. I’ve read of others that have had this problem and saw pics of carbon-ed oil rings and pistons. Apparently the boxer lends itself to this type of problem when you are not super critical about frequent oil changes and synthetic oil. The owner has been doing his own oil changes at an interval of 4-5k miles with low cost dino-oil. This, along with the customer working at a local university and only driving 3 miles each way to work lends me to think that stuck oil rings are a strong possibility.
I’m trying to devise a plan and my first step was to find a solution that would completely dissolve carbon from a piston without having to scrape, scour or rub to accomplish this. I went to the lawn mower shop and found a nice crusty specimen piston, probably out of a V-twin zero turn. I then gathered up a bunch of snake oils: Fuel oil, ATF, MMO, Motor Medic, Autozone lifter treatment, Berry carb cleaner dip, brake cleaner, MEK, Acetone and Simple Green. I tried soaking piston in all solutions for 4-5 hour periods in non-diluted compositions on a portion of the piston. The only one that had any noticeable effect at all was Simple Green. I even tried combinations like Diesel and carb cleaner, MMO and Acetone etc. After a 12 our soak in Simple Green 98% of the carbon was completely gone and the portion that was dipped is like brand new. There were a couple of little spots of carbon that were still present. This concerned me as in my mind this extra tough carbon represents the oil return holes under the oil ring. I then soaked it for 12 more hours and 100% of the carbon was dissolved. I have repeated this experiment with Simple Green and I’ve had the same results.
Assuming the engine runs good, has good compression and a borescope shows no scored walls I would like to try soaking the oil rings with SG. The question becomes how to accomplish this and how to clean up afterward. My thought is to drain the oil, replace the oil filter and then over fill the crankcase with simple green and allow a 24 hour soak. I suspect the SG would find its way into the combustion chamber so I plan to drop the exhaust manifold to avoid getting stuff in the cats. After the 24hr soak I would flush a second time with SG in an attempt to flush more solids out. Next I am thinking about flushing the crankcase with a mixture of 90% diesel 8% motor oil and 2% 911 (water dispersal) to flush out more solids and the Simple Green that may still be lingering. This followed with a couple of fast oil changes.
Prior to the attempting the fast flush I started with a slow flush. We added MMO and 200 miles later I added a half can of Kreen (Nano Labs internal engine cleaner) and the customer is currently driving the vehicle. This will probably go on for 200 more miles before I drain it out and start the fast flush.
So now I’ll put my bullet proof vest on and ask for your comments and what you think my pitfalls will be . I’ve probably missed some obvious things, there may be some hidden dangers and some will question my sanity but that’s why I’m posting. Thanks