I have looked in the lubrication thread and after reading 20-30 posts thought that I would just ask for some help. I have 1990 mark 4 454's that are normally asp. and dynoed at 469 hp. Since being built (130 hrs) have run Royal purple 20/50 XPR without problems. But now hear that RP is not as good as once was. I want to do an oil change and have found out that no-one now carries the stuff in my area.
What can be recommended to run for my engines and find easily without ordering it somewhere? Live in small town in Miss.
Also would like to stay with synthetic.
Thanks

Mobil 1 15-50

been running royal purple for years and not changing....if you have had no issues why should you ? I have not heard anything about not being as good....they all are losing some additives due to emissions....Rob

The main reason swapping from Royal Purple is because of the un-availability in my area. You just don't go down and by a couple quarts.
Thanks for the advice.

Is Mobil 1 15/50 fully synthetic or synthetic blend?

Full synthetic.

Thanks for the help.

I saw a Royal Purple analysis still looks fine.

NAPA carries it. Got one near by?

Ditto ............