HM oil vs Syn.

[edvanp]

If a car has received regular changes of synthetic oil (M1, NAPA or Castrol..whatever is on sale), is it necessary to use HM oils for seal protection?

 

[Schmoe]

If it ain't broke, don't fix it. The seal continuim is a never ending topic on this board. A LONG time ago, synthetics were known to affect some seals, but that has since been rectified. Actually, some HM oils have in it what synthetics already have to "condition" the seals.