Even though I'm about 1000kms/600 mi early, I took the plunge today and went to Mobil 1 10W30 with an AC Delco PF52 filter in my '96 Yukon (5.7L Vortec) with 190100kms/118000mi. Something I never really considered: What kind of chanage interval should I be looking at? I have always been religious about 5000km/3000mi changes in the past, but have heard that synthetic extends the interval significantly. I just short-changed twice. Right after I bought it at the beginning of May (even though the dealer said they changed it before I picked it up, I wanted the peace of mind) and again at 3000kms to help clean it out if there was any junk in it. Recommendations? This is the first time (that I know of) that the truck's ever seen synthetic.