more cars are using synthetic oils , and you say not to use mmo in synthetic oil are you putting yourself out of business of selling mmo slowly?

MMO is not just for putting in the oil you know. I run it all the time in all my engines’ fuel. Marvel is not saying not to put it in synthetic oils but many of us on this forum don’t think it’s a good idea to risk messing with the additive package in a fresh change of top tier (group 4 or better) synthetic oil. I run long intervals and still use MMO in my oil, I just wait until there is about 3000 miles left to go before the change to add the MMO. The additive package is plenty used by then and the MMO will help fortify the old oil before it’s changed.

Cost alone will keep many from using synthetic oil, especially as the vehicle ages.  MMO will continue to be popular with those who are familiar with it’s benefits.

Nope....nil.  MMO has other benefits.......I believe my mother’s 2010 Kia Optima to have outrageous OCI......and it specs synthetic oil according to her (I’ll let her be the jidge there....Im not tearing thru her manual), and so I’ve got her on a 3k treatment rate, towards the END of her OCI, I put a pint of MMO into her engine......of course, not allowing the engine to over-fill.....as I feel it will help “clean up” what may have gotten dirty during these extended OCIs......

Thats bull butter. I run MMO with synthetic all the time. It actually works pretty well.  I just add a pint and run it the last 1000 miles of an oci.