Yesterday it was boiling hot, (major understatement). I had to remove and clean the injectors and pump on an old diesel tractor. So - drive into the field, remove the "stuff," drive to the shop, clean, drive back, install, drive out of the field. It was only then that I noticed my temp gauge was at 260 degrees, (pegged). Turns out that the seeds from all that johnson grass had packed themselves into the cooling fins of my radiator. Turned the heater on high and made it back to the shop, (to top it all off, I was wearing a black tee-shirt). I would have drank water out of the toilet by the time I got back. Now, I just changed the oil about 200 miles ago on this truck. Did this running excessively hot journey shorten the life of my motor oil. It's still clean and does not smell burnt - but - did it change anything chemically? The oil is 10 W 40 Super Tech API SL. Truck is a '96 Chevy 305 V-8 with automatic tranny. 120,026 miles.