Running Rotella T6 5W40 for the last couple changes.
It's developed a lifter tick at idle after an hour or so highway driving.
around 65-70 PSI, once there is just a little throttle opening, pressure goes to 80PSI,
the bypass must open since it's a hard limit, maybe at first startup on a cold day I'll see 82PSI.
I've let it idle for over an hour on a 100F day with the AC running, not enough to get the tick.
Thinking of going to the next higher vis, Mobil-1 15W50 is what I'm looking at,
looks like good Zinc, Phos for this older bigblock with that gets run hard on the highway.
Out West on a long climbs , I've had it WOT for over 20-30 mins ( Capitol Reef on I70) or US80 in NV