Why wouldn't the station owner just temporarily 'T' the line from the regular line to the premium line at the pump rather than involve others and increase risk for himself?
From the original picture you posted it shows 0W-30 or 5W-30 as acceptable grades (no mention of 0W-20). Unless that picture is from somewhere else than the manual?
I have bought 5 NOCO chargers(1A, 2A, 5A) , 2 off them have already failed.....I think they do a good job while they work, but not impressed with the longevity at all. Wont buy anymore.
I would up to at least 5W-30 if towing, probably Mobil 1 0W-40 which is a thin 40 grade. Or go with a 15W-40 if towing often and climate allows, which MS certainly does.
A proper stump grinder takes a lot of HP - all of it. Definitely not worth trying to build. Unless you already have a 40+hp coming out of something, even then.....just rent or hire.