Take a deeper look into the extended range oils offered by mobile 1 if you ever think about purchasing them. I've heard reports of people getting weird analysis of them. Like the 10k mile oil's viscosity will drop mid service and then return to spec at the end. So you take a new sample, checks out fine, mid change (like 5k), it's dropped below spec, then at 10k you're back in spec... pretty shifty stuff.