Engine oil and fuel questions

[Splorg]

Sorry for what are likely a few dumb questions in advance.

My 2001 Yukon (5.3L) has 251K on the clock with the factory engine and transmission. As far as I am aware (and with so many miles in my experience) maintenance was regular and appropriate for the vehicle. However, I have absolutely no idea what was done aside from what repairs the gentleman I bought it from last week performed - new alternator and fuel pump, new accessories drive belt, plugs, and wires.

The oil isn't hatefully dirty or anything, but I'd like to get it changed. Beyond the viscosity required, 5w30, does anyone have any guidance as to what kind of oil to use given the high mileage, or any other tips?

As well, since it isn't labeled to take flexible fuel, I know not to try E85, but since it is a 2001 model, is it safe to run E15?

Thanks!

 

[SnowDrifter]

Stick with E10

Use 5w30. I personally don't subscribe to high mileage oil or any of the other bottled nonsense. Only reason to deviate is if you had rod knock or something and you're trying to limp the motor through, in which case, it would be more appropriate to use a thicker oil due to larger clearances.

And use a quality filter. I'd rather run cheap oil and the best filter to make a budget than the other way around. No matter how good your oil is, it'll do you no good if you have abrasive crap going through the sump!

Edit: If you're towing heavy with it, I wouldn't sweat stepping up to a 5w40. Not necessarily because thicker is better. But because higher temps will thin the oil out on its own and at that point, a hot 5w40 would be similar in viscosity to a daily driven 5w30. Whereas 5w30 might border on too thin. Disregard that if you have an oil cooler though.