The last OCI, in January, was with 20% (1.5 quart) Marvel Mystery Oil (MMO) in Rotella Conventional 15w40. That was a clean-up run on the newly purchased used 2003 Deville. I had replaced it for this last OCI with what I normally run, straight Rotella T Synthetic 5w40 (RTS). I had an analysis run after the first OCI just out of curiosity about the MMO.
After seeing the exceptional wear metal numbers with 20% MMO, I decided to run another analysis with this straight RTS to get something like a baseline. The numbers looked almost as good. I'm trying 20% MMO in RTS this next OCI and I'll run another analysis at the next change. I know I may be raking around in the "noise level" of the measurement process comparing numbers this low, but it interesting to see that the MMO not only did not hurt, but if anything it helped, and that this Northstar engine seems to love the Shell Rotella products.
The dipstick level had dropped about 1/2 quart the first OCI with no make-up oil and it dropped about the same - maybe closer to 1/3 quart - this time. I saw no evidence of significant leaking or "burn-off" with the MMO in this engine which was interesting, because I have seen MMO when run to quiet lifters cause excessive oil loss in older engines.
After seeing the exceptional wear metal numbers with 20% MMO, I decided to run another analysis with this straight RTS to get something like a baseline. The numbers looked almost as good. I'm trying 20% MMO in RTS this next OCI and I'll run another analysis at the next change. I know I may be raking around in the "noise level" of the measurement process comparing numbers this low, but it interesting to see that the MMO not only did not hurt, but if anything it helped, and that this Northstar engine seems to love the Shell Rotella products.
The dipstick level had dropped about 1/2 quart the first OCI with no make-up oil and it dropped about the same - maybe closer to 1/3 quart - this time. I saw no evidence of significant leaking or "burn-off" with the MMO in this engine which was interesting, because I have seen MMO when run to quiet lifters cause excessive oil loss in older engines.