The car
-2008 Subaru Forester Sports XT w/ VF48 turbo, 285k miles.
-185k miles on this OEM short block.
-Fresh turbo rebuild
-Eats 1qt of Rotella T6 5w-40 every 250 miles.
-Noticeable pre-ignition at low RPM, car falls on face and bucks if you add load below 2,500 rpm. You have to gently get over 2,500RPM, then it runs normally. My assumption is the blowby contaminated oil is just entering the combustion chamber. Could be via ring seal, breathers or combination of both.
The compression is pretty consistent except for cylinder #1 at 135PSI where the others are 145-150PSI. My plan was initially to just buy an OEM short block, have the D25 heads rebuilt and rock on for another 180k miles. I've tried soaking pistons by putting B12 into the cylinders, but this being a boxer engine makes that peculiar. Cylinder #1 spark plug has noticeable contamination.
Out of curiosity, I figured before I spend $2200 on a new short block from Subaru I'd try this liquid mechanic. I'm 1,000 miles into running 5w-30 Restore & Protect and the car has required 1.5-1.7 qts of total top off in 1k miles instead of 4 qts (1qt per fill up). Immediately after changing to R&P the misfire improved dramatically, no longer immediately falls on its face. The misfire improvement I'm assuming is the old oil was EXTREMLY contaminated, so any fresh oil would have helped.
It's too early to call it, but something has changed in this cars oil consumption after swapping from Rotella T6 to R&P.