Here are my thoughts;
LB7's are more prone to higher oil temps, why, I am not 100% sure, but it only seems like fluctuating oil pressures are tied to the LB7's..
I never did any oil testing in my LBZ when I had it, mainly because I didnt know much about the topic either, but, when I would tow 14k to the dunes (weekend warrior full throttle) engine fan would kick on about 230* ECT, im sure oil temp was through the roof. I wish I did testing on it.
On my LB7, I knew oil temp with twins was an issue. I bought my truck knowing it "overheated" while towing, which was true, but it wasnt the coolant that was overheating, it was the oil. To test this, I towed my 26' gooseneck that is 5k lbs, up to northern AZ, from 1300' to over 7k. Results shocked me. Oil temps ski rocketed to over 260* pre OEM cooler, while climbing in 4th gear at 60 mph to keep the EGT's in check, coolant fan came on once, then back off. Stock trans cooler, and no additional oil cooling, other than stock. Reason why it was overheating the coolant. In that case, the hot 260*+ oil was preheating the engine coolant from the cooler, offloading it's heat into the coolant. Now my engine had to deal with that, as wel as higher temp coolant fromt he engine working harder, and it only got worse the higher the oil temp got, then oil pressure gauge would go :dancenana: from 30-65psi.
Bought Killerbee engine oil cooler, "new used". Oil changes are now 14 qts. Hooke dup trailer, same route there and back, same trailer. Never got over 190* oil temps, again, pre cooler. Engine fan never came one, but efi showed 195*, normal. Cool, it works. To put into a BTU perspective, my cooler is 140,000 BTU's.
This past weekend I towed 1000 miles a CC/SB LB7 to Mike L's. There is a 17 mile grade from Palm Springs, CA back into AZ, and wery windy at times. I was towing ~14k. 55mph in 4th gear up the hill, for 10+ miles, coolant reached 210*, oil reached 220*, again, for 10+ miles. The one thing I noticed with oil temps vs EGT's, is that if you lug the engine up the hills at 1900-2200 rpm egt rises, but oil temp does not. I felt it was easier to downshift into 4th gear to aid in higher boost and lower EGT's' but oil temp would rise, kind of a tradeoff, as you can't have both with big twins.
Around town my coolant never goes above 180*, and slows warming up around 164-175*. Oil temp sits are 180* no matter what, unloaded, and now loaded on flat ground. Your going to make heat period on the hills, but a biggert cooler cannot possibily stop rising oil temps, but it does help "cusion" the spikes. 220* is still hot, but for the load I was towing, combined weight, and air temp, that was cake for my engine. I only have about 2300 miles on this cooler, but I would spend the money again, but only if Super Diesel made a kit. :thumb: BTW, I have MPI big twins, 366/480, 30% injectors, stock CP3.
Sorry for the novel, just wanted to share my findings. :thumb::thumb: