Time Out Please, side bar on multi wt vs versus straight wt:
When I was hauling logs in the 70s we used straight 40 wt in the 855ci Hercules in our '42 Federal 6 by. It got HOT when we worked it hard, and it used quite a bit of oil. One day (I was out of town) my dad and brother apparently couldn't find any more 40wt so the dumped in a couple gallons of 10w-40. Lost a rod same day. Fast forward to the mid eighties. I was working on the North Slope in the arctic in the winter (-20F), everything ran 24-7 with straight 30wt. I asked why they didn't use the new "Frigid Go" multi-vis oil, and was told "We used to, but lost too many engines". That was 40 yrs ago, but still I have this nagging suspicion that the multi-vis oils do not really have as much viscosity at high temp as the old straight wt oils. I still run straight 40wt in my two vintage Detroits, and straight 30wt in the Continental flathead in my 50-something Hyster forklift. Are there not a whole lot of air-cooled Harleys out there still running a straight wt oil? And airplanes also? I do run multi-vis of course in all my autos & motorcycles, including my '73 F100.
I haven't actually done this, but I think it would be an interesting "real world" test. The 360 in the F100 is getting tired, oil pressure not what it I would like to see, so currently running 20w50 racing oil. I wonder if the hot-run pressure would go up if I changed to straight 50wt motorcycle oil or airplane oil? Obviously NOT good for start-up, but strictly for the comparison of straight wt vs multi-vis at hot run, would be interesting to see what it does.
What do you think?