Today I was at the Home Depot and figured I'd grab a few big jugs of oil to change the Gladiator and the XJ (both with a 4.0). Normally I use Mobil 1synthetic 10w30 with a Mopar MO-090 filter which I buy by the 12pks. My Gladiators 4.0 idled around 43 psi and my XJs usually idled really low around 18psi. Today I bought Pennzoil Platinum full synthetic 10w30 since they didn't have Mobil 1 and my truck is now idling at 58psi and my XJ at 40psi. 3 years owning that XJ I've never had oil readings like that, and ive used Castrol as a substitute in the past a couple times. Think I'll stick with this brand going forward. Happy with the pressures as now the XJ is more where it should have been all along. I just wanted to tell someone this because it makes me happy and everyone I know around here could care less about my jeeping and shop antics.
But we do care......and keeps us coming back for the next session
'81 CJ5 Base, 258 I6, MC2100, T176 4 spd, 300 TC, D30 Front NT, 3.31, 2-Piece AMC 20 rear NT, 3.31, 4" high arc spring lift
'84 Grand Wagoneer, 401 V8 (.030 over), MC2150 HA Comp, 727 auto, Selec-trac NP229, AMC 20 REAR - D44 FRONT - WT 3.31, 4" high arc spring lift
Rather be driving, than waiting to be modified
Somewhat related, I've been using amsoil z-rod 10w40 and after long highway runs my oil pressure would get scary low at idle. Dropped some napa 10w40 dino oil in it before a 1,000 mile trek back home and highway/idle pressures are much improved. One would think the oil rating describes actual viscosity at differing temps but there's something else at play here.