Originally Posted by bluesubie
If you aren't having leaks then you may not need to switch. The Mobil1 HM oils have additional seal conditioners, have a thicker viscosity within the same grade, have a higher High Temp High Shear, and have more anti-wear additives when compared to the regular oils. There is an M1 5W-30 High Mileage oil. Some people run them just because they're more robust.
Thanks for all the info! I guess I'll be sticking with my mobil1 5w30 and 5000km change interval since weight is not a big factor. Never seen HM 5w30 Mobil1. I'll have to check that out.
Regarding all the leak comments, I did have an oil leak but had the PCV valve and seals replaced so everything is better now.