The next test came a week later. I took the family on holidays through Montana. The temperature exceeded 40 C and the speed limits are high. The truck performed flawlessly, and did not use any oil in 2000 kilometres of driving. I also notice the oil pressure gauge remained in the normal range with the engine idling, instead of dropping to the low end of the scale as it has done during previous hot weather driving.
Several cars require synthetic engine oil to meet the manufacturer's warranty requirements.
Typically, these are high performance vehicles that generate a lot of heat in the engine during spirited driving. Synthetic oils provide the extra protection during hot engine conditions. It was only a few weeks later that I was able to check the oil performance during cold weather. While we have not reached the frigid temperatures of winter, the temperature has already dropped to -14 C where I was driving. I noticed the engine cranked quickly, and the oil pressure rose immediately upon starting the truck.