Orcrone, I tend to agree with you. In fact, I bet the sludge came from a combination of things, one of which is extremely high mileages between changes... something like way over 10,000 miles...(I panic if I get to 5,100 and haven't changed mine yet). Perhaps in these cases, where folks are unable or unwilling to change at 5,000 miles, synthetic oile would be a benefit.

I only referenced that, in reply to skywagon's comment:

"My engine never got sludged up because i used full synthetic right from the first 1500 miles."

He seemed to infer that dino oil wasn't good for "...extended oil change intervals like the manual called for..."

I believe that the manuals today call for 5,000 mile changes, is that really extended??