I was wondering what is acceptable motor oil temperature and transmission oil temp I have a 87 fiero 2.5 with sensors on both with coolers and pressure sensors and fans ...I like to know what the hell my engines doing while I drive... my trans temp with out fans running goes to 90 C during summer and my motor oil goes 50 to 60 C with fan running I run 5.5 qts of oil with my oil filter relacation kit and cooler

On a hot engine, oil is expected to be about 15*F hotter than coolant... so when the computer takes over the engine in closed loop, about 180*F, the oil would be 195*F or about 90*C. If you are using an external heat exchanger on your oil and keeping it down to 60*C, you should probably use a thinner oil than recommended.

my fiero is a lambo replica now . so my transmission oil going to 90c is okay right? what is too hot? my oil temp getting 60 c is ok but I need to use thinner oil? I use 10w 30 pure synethic so I need like 5w 30? thinner oil is needed for the colder temps rights? I live in texas wheather is weird thanks for the info im having a overheating problem due to the car being heavier or not burped right so I installed dual trans coolers with 2 10 inch fans and a cooler with a 10 inch fan for motor oil with an oil filter relocation kit. im not using oem transmission line to radiator I decided to do a dual cooler in rear

All the fluids were designed to be operating at 90*C with no problem, and considering how much better synthetics are, I doubt if you really need to change anything, but If you are driving short distances in the Polar Vortex, 5W-30 would be a good choice I think. A better fix would be to take care of the overheating problem.

An important point here is that both temps get high enough to boil off condensation so that it does not build up in the fluid over time. Hot engine oil and good oil pressure at all times is no problem, automatic trannies live longer with lower avg temps over time as an engine failure due to overheat is usually followed shortly after by a tranny failure after it is repaired since it overheats along with the engine when cooled by the engine coolant only.