Hello folks: I have recently acquired my fathers old truck, a 2002 5.3 Silverado. Truck is closing in on 250k, and is nearing an oil change. I have been contemplating what oil I should go with. I was debating on if I should go with a high mileage oil, or just use a good name brand synthetic. The truck won't be a daily driver, but I would like to keep it in the best running shape possible as there is a lot of nostalgia attached to it. Most of the driving it will see will be just local backgrounds and occasional trips to town. I was considering using a high mileage 5w-30 thinking it would be beneficial to the 250k motor. However, I am hesitant because my father just had all new seals put on (valve covers, oil pan, rear main, even o-ring on dipstick tube) less than 10k miles ago. Would there be any benefit to using a high mileage oil with all new seals? Any risk in using high mileage on new seals because of the conditioners or swelling agents? Aside from seal conditioners, are there any extra additives to high mileage oils compared to their non HM synthetic brothers? I ask this because on a bottle of mobil 1 high mileage I had in the garage, the star chart on the back claims it protects "high engine temperatures" better than regular mobil 1 Any high mileage oils that offer good protection without attempting to swell seals? If high mileage is not the route to go, what is a good synthetic for a high mileage vehicle? Best filter for high mileage 5.3's? Also, if it matters, my father wasn't an oil stickler like I am. The truck has probably seen conventional oil for 90% of its life. Should I stick with the conventional if that is what it is use to? The truck doesn't burn or consume any oil as far as I am aware, but I have only had it for 4k miles. If it does burn or consume, it is very minimal. Thanks for any input and advice in advance.