I have experimented with back-to-back runs of Rotella T Synthetic 5w40 with and without 20% Marvel Mystery Oil in my 2003 Cadillac Deville with a Northstar 4.6L engine. I have posted the UOA information on these approximately 5000 mile runs in the Used Oil Analysis - Gasoline forum. All the wear numbers looked good for all the runs, with slightly better iron (7 instead of 9) and copper (4 instead of 5) numbers for the ones with the Marvel Mystery Oil.
My awareness of Marvel Mystery Oil being used to solve problems - like dealing with valve lifter noise - and being used to generally clean engine internals spans more than 40 years, but I've never before thought about using it all the time. I am now.
I have seen it work well for what it does many times, but I've also seen it make leaks in some older engines significantly worse while it was in them. That hasn't been a problem with this engine, though.
So my questions are:
Is the improvement from 9 to 7 in iron a reason to continue using Marvel Mystery Oil in otherwise normal oil changes?
If Marvel Mystery Oil is used routinely for oil changes, will there be any difference in seal and/or gasket leaking at high mileage?
My awareness of Marvel Mystery Oil being used to solve problems - like dealing with valve lifter noise - and being used to generally clean engine internals spans more than 40 years, but I've never before thought about using it all the time. I am now.
I have seen it work well for what it does many times, but I've also seen it make leaks in some older engines significantly worse while it was in them. That hasn't been a problem with this engine, though.
So my questions are:
Is the improvement from 9 to 7 in iron a reason to continue using Marvel Mystery Oil in otherwise normal oil changes?
If Marvel Mystery Oil is used routinely for oil changes, will there be any difference in seal and/or gasket leaking at high mileage?