i live in texas and drive mostly city and race. what would you reccomend?? and is royal purple good or bad?
If you've ever changed your oil on your diesel truck (I've been changing my own for the past 40 years), you'll notice that the used oil has a lot more contaminates (why else would it be so black?) in it than what comes out of a typical gasoline engine.
I know that synthetic oils don't break-down like regular oils, but they still get dirty from engine deposits and those deposits aren't removed from your engine until they run through the filter, so on the way to the filter the deposits can do damage.
Forget Royal Purple or any other synthetic unless you're going to change the oil at 5,000 mile intervals or less, if you are going to be doing a lot of Racing.
Stay with a good quality conventional oil (Shell Rotella, Chevron Delo 400, or Motorcraft) and change it every 3,000 to 4,000 miles and you'll never have a problem.
Oh yeah, if you're on a road-trip and by chance need oil, don't plan on finding Royal Purple or many of the other synthetics just anywhere. You can always find Rotella.
The following information has been offered as "an opinion" and should not be construed as "bashing" or "promoting" any oil.
Be leery of those on the forum selling Snake oil.