Originally Posted By: badtlc
Using MMO with the oil is fine, but if you want to get the most out of the oil, then wait until the last 500-1000 miles to put the MMO in crank case. Otherwise, running the MMO with the oil for the entire OCI will decrease how far you can extend the OCI.
I agree. MMO lowers TBN according to used oil analysis reports. The used oil analysis reports I've read with MMO added were all pretty impressive, but TBN took a slight hit. My thinking is this: if you want to clean an engine don't use MMO for an extended drain, a 3,000-5,000 mile OCI is fine. If you want to clean the engine then you want to get the dirty oil out, not leave it in there for an extended drain. If you want to do some light cleaning or keep an engine clean, a pint of MMO for the last 1000 miles or so of an OCI is the way to go.