The 3,000 mile belief goes a lot further back than Quiklubes. I remember a guy telling me about that back in the late 60s. I followed that rule right up through the late 70s. I also changed the filter with every oil change
3,000 miles was easy to figure out because any number with a factor of 3 in it is divisible by 3. I could just look at the first two digits of my odometer and note right away whether it was due for an oil change assuming I changed my oil at virtually 3,000 mile intervals.
I don't remember what kind of synthetic it was but NAPA auto parts sold it.
What is an average price for a quart of synthetic? I remember when it first came out it was pretty spendy.
Also, is it a good choice for an $80,000 car?