Load,
I understand your doubts, I had the
EXACT same fears. The proof in my case is I've driven on 38deg days on highway [after a slow warm-up to t'stat temp, gearbox and diff] and easily maintained 190 - 205. Down by the beach, at big rpm/mph - in fact the more rpm, the more stable the temp. You just have to be patient and not hit it cold.
Bad news for me is
oil seldom gets above 140 in those conditions in spite of blocked cooler and
oil t'stat. In fact one year, I disconnected the cooler LINES, capped everything and ran
oil in the motor only. Barely made a 10 - 15 deg improvement. I love 10-30 Mobil One for exactly that reason.
I even drilled a 1/16 hole at the top of the 195 before installation. No problem.
Good luck, keep posted.