19oF this morning.
2000 F350 with 220K miles. It got 4 times to crank. It so hard. Going need switch cheapo supertech 15w40 to Shell 5W40 I had in garage.
If it was me I would plug block heater 2 hours min.
Last year I had 87 F250 with 6.9L diesel. It was PITA. Thank god it had brand new denso starter from preview owner. It would shake whole truck for about 5 min with tons of smoke out exhaust.