Originally Posted by kstanf150
Unless somebody has proof that I've never been able to find.
Nobody really knows for sure what HM oil really does or doesn't do. I'm of the opinion that HM oil is just another marketing plan to get buyers to pay for something they don't really need. I'll admit I've been tempted to try it, but never have because I've logged a lot of miles on regular Dino and synthetic oils that were not HM.
Most HM oils have a slightly higher percentage of seal conditioners and in most cases, the basic viscosity is slightly higher as well.
Most seals are elastomers,and seal conditioning chemistry replaces some of elatomer molecules that have been lost to wear and heat.
Are HM oils another avenue of income for oil manf., of course, but they also help high mileage engines in various ways.