On Tuesday, February 5, 2019 at 9:03:06 AM UTC-5, Rob wrote:

Those times are probably not long enough. Even in my small car
(4-cyl 1.6L engine) I find that after a lot of 15-minute runs the oil
temperature caps at 100C when driving a bit longer, and it requires a
45 minute drive or so before it rises to 110-120C.

15 minutes at 1,000 rpm sitting still (using only the radiator fan if needed) is substantially different from moving down the road. Not to suggest that you are wrong. Every engine is different, and the goal is to drive all the moisture products-of-combustion out of the engine oil and exhaust system.

Peter Wieck
Melrose Park, PA