> "Haut category," I reckon it would be called in the professional bicycle
> tours circuit.
>
> A two-lane road, we climbed and we climbed. The oil temp gauge hit 235,
> easily. Hottest I've ever seen it. I was in first gear (auto trans) and
> kept
> the rpms to 3100.
>

  Hors category. climbs..or 'HC' in a bicycle Grand Tour....those are climbs
with long sections that are around 20%.   A 20% climb is rarely encountered
in the US and will 'get your attention' when driving a vehicle...

  Lombard St. in SF was laid out in switchbacks to reduce the grade to 17%
because most cars are incapable of climbing the 27% natural grade of that
hill.

  The grade of Tioga Pass into Yosemite was laid out at 7% max.  Sonora
Pass, the steepest pass in the Sierras, averages just over 7% with a few 21%
sections..It is given a category 1 classification....one category under an
Hors Category rating...by Daily Peloton web.

The most sustained gradient I have encountered in the western US is
Montezuma Grade on the east slope of the mountains near San Diego...it
averages ~8% for 10+ miles.  I took my one test ride in a Diesel Westie on
Montezuma Grade and was passed, going uphill, by my 55yr old wife riding her
bicycle..

  I'd just change the oil..I usually change my oil after a prolonged high
speed journey anyway...
  That section of California can get really really hot!  I raced my black
car once at Thunderhill Raceway Park, near Redding, on a day when the temps
were recorded at 123F!  My oil temp went just above 300F.  I bought ice
water circulating cooling vest to wear after that race.