I thought I would post some observations regarding oil temps. I did this a few months ago when it was in the low 80's and the water temps were about the same. I put a temp gauge in the port just above the oil filter location on my 4.3 and it worked great. Cruising was for 5 plus minutes. I only did full throttle for a few minutes. I was idling it for about 10 minutes to cool the oil down. I plan on getting an oil cooler after seeing the results of my testing. When I do I will post the new temps.
idling 600 rpm engine temp 165, oil temp= 175
cruising 2600 rpm engine temp 165, oil temp = 205
full throttle 4800 rpm engine temp 170, oil temp = 270 and climbing
idling 600 rpm engine temp 165, oil temp= 175
cruising 2600 rpm engine temp 165, oil temp = 205
full throttle 4800 rpm engine temp 170, oil temp = 270 and climbing
