The advantage to
synthetic is cold starts, where all the wear takes place. $50 for
synthetic at Walmart (Mobil 1 5quart jug is $24.50) compared to $30 (Valvoline $15.00 for 5 quart jug) for non sythetic at walmart. My
oil changes require 10 quarts. For $20.00 I will splurge on
Synthetic.
In my opinion the optimuim
oil is Mobil 1 0W40, followed by Mobil 1 10W40 high mileage for Hot climates as in Texas.
15W50 is way to heavy. I put some in and drained it out 5 miles later when the
oil gauge was pegged at 60 psig and ambient outside temp was 90F. The last thing I want is the oil pump bypassing and the second to last thing I want is the oil filter bypassing.
I found an interesting study, most oil filters at 6600 rpm and 10W30 have a pressure drop of 15 psig across them at 100C oil temp. Most oil filter bypass at 9-11 psig. The Ford Racing FL-1HP bypasses at 22 psig. So in summary most stock filters are not filtering your oil at high rpms. Probably not a big deal but something to consider.