The NAPA
oil (high in ZDDP) or Rotella, as well as a number of other ZDDP bearing oils, cost about half of what Brad Penn goes for. The cost is a factor when your using a LOT of
oil. Because of the limited number of miles any of my vehicles actually see I generally change it based on "time" rather than miles, but that depends on use. Often that becomes a marathon fleet
oil changing time, a time I don't generally look forward too.
$10 a gallon compared to about $20 a gallon, in round numbers. I add two bottles of STP at about $2.50-$3.00 a bottle (say $6.00 total). I buy oil in the gallon or more jugs at a time. The truck and the Cobra will consume over 4 gallons alone, not to mention the other vehicles around the place. All of them get the same oil and a shot of STP according to their need.
I've been using STP since high school, seems to work, who knows for sure? I never did put much faith in "testimonials" (mine or yours
) as I prefer hard numbers. But heck even "studies" and "polls" remain suspect. Good write up on Brad Penn, even though it is from a potentially biased source, I have a hunch it's the "good stuff", but a bit pricey.