Hey all long time lurker, I've been given a 2005 gmc jimmy from my dad, which sat for 5 years in his garage. With all the reading ive been doing the 4.3L is not a picky engine when it comes to oil. The suv has 164k kms (101k miles) and my dad always changed the oil at 4k with 5w-30 green quaker state and orange fram filter when he drove it. So before he handed me the keys he told me he did an oil change, and full engine tune up exactly 1 year ago. He did not put any kms on, but he would start and let it idle for 15mins every friday after work. It doesn't leak, or burn oil within the 3 weeks ive been driving it. I put appx 45-55kms a day driving kids to and from school and to work. Mix of highway and city stop and go. Only fluid im losing is ATF, but not too worried about that right now. So my question is does my Jimmy fall under the HM oil category? Or just stick to any conventional oil that is on sale? I read numerous threads that HM oil helps with seals and leaks, but mine is not leaking at all. And what would be a good baseline mileage to do a UOA for HM (M1 or Valvoline Maxlife) oil? 8000kms (5000miles)?