Talking air cooled here but I guess it applies to anything, My question is everybody talks about sump temperature, and even an oil thermostat tries to regulate sump temperature, wouldn't the oil temp going into the engine after the coolers be more important. does anyone have any input or figures
The oil temp is important because it determines the viscosity, shear index, etc, etc. The important bits in an engine that rely on the oil viscosity/shear index, etc are bearings especially. Figuring out the oil temp AFTER it comes out of the bearings is probably more meaningful than the oil temp out of the cooler, because after the cooler it still has to go through the pump gears and the case/block before reaching the bearings. Temps immediately after the bearings show what oil quality the shells themselves are dealing with.
As a rough guide only..........
80*C -- good
90*C -- OK
100*C -- just OK
110*C -- getting too hot
120*C -- too hot
Hope it helps. 🙂
I always measure the temp after the cooler, this way you can manage and vary the temp using a electric fan, if you know the delta t across the cooler you can work out the oil temp entering the cooler, I also have a digital controller in the same position to turn the fan on and off, if you have a IR gun you can measure the block and in my case on all my cars it is hotter than the oil by up to 20 degrees C, if the sender is in the block it will be reading more the block temp rather than the oil temp, in my ghias set up the oil never goes over 100 degrees, I have a inline thermostat and a large oil cooler with dash ten hoses, I also have a scoop under the car to direct a good flow of air into the cooler when at speed.
Thanks Monrod the temperatures you quote agree with what I have been working with, the coolers are after the pump , I am well aware how important oil temps are that is why I asked this question.
vwo60 like you I am running 2 remote coolers one 97 plate to the front of the buggy and a 47 plate at the rear, front with forced cooling plus a fans for both which are switched from oil after the cooler, the fans only switch on when the car has been stationary for some period of time, I too have an oil thermostat that works somewhere between 80 degrees C and 100, it is a good aircraft one not one of those nasty empi ones that I had to throw away on my trip to the Cape, I have not measured my return oil ( which is returning directly to the oil pressure regulator not the oil pump ) but I can say that at a sump temp of 100 degrees C you can hold you hand on the return line which would probably indicate to me that the oil is too cool ie less than 80 degrees. I am going to hook up a second oil temp gauge to monitor the temp before it returns to the block.
get a IR gun and you can measure the temp anywhere on the engine.
Yes I will do that they are quite reasonably priced now
