1955firstseries Should work for you,even in your colder climate,klhansen uses it clear up in Alaska. I would help it a little with zinc additive (I do) to protect that expensive hard to change cam. Maybe your truck sleeps in where it is warmer. Once got a lesson on crazy oil pressure in a 540 chevy truck pulling engine,turned out our machine shop's sloppy align-bore work left the rear main cap leaking oil internally right out in the way of the 8'000 rpm crankshaft making it foam. O-ringed the leak,that nitro Merlin block is headed for season 12 this summer. Any erratic oil pressure is often related to foaming oil. I have used 5w30 here in cold/hot Il. since 93 haven't lost a bearing,no oil users, just lately started using 0w20 as instructed by warrenty. Use zinc additive in flat tappet engines as I said some are 50 yrs. old one is 75.
Last edited by fixite7; 04/26/2023 10:54 AM.
