Oil pressure changes with ambient temp changes

[Donald]

If it's cold out, thermostat operation will limit how much of the block coolant gets diverted to the rad, so rad bulk temps can be quite a bit different from engine bulk temps. So, if the oil is not on a thermostatically controlled circuit and getting cycled into the rad, if the rad is 15-20 degrees colder than the coolant in the block, that's going to reflect in oil temps.

On the other hand, applications with a block-mounted heat exchanger that uses block coolant as the heat transfer fluid, temps are going to be much closer coupled.

I thought mainly cars with turbos had oil coolers to cool oil that was heated up by the turbo.

I would think you want to oil entering the block to be at engine operating temp to provide the best lubrication. You are not expecting the oil to provide any cooling. Maybe your oil cooler is cooling the oil too much.

 

[OVERKILL]

I thought mainly cars with turbos had oil coolers to cool oil that was heated up by the turbo.

I would think you want to oil entering the block to be at engine operating temp to provide the best lubrication. You are not expecting the oil to provide any cooling. Maybe your oil cooler is cooling the oil too much.

The OP says his oil cooler is in the rad, so it would be subject to fluctuating coolant temperatures in the rad if it's not thermostatically controlled (the oil cooler). Both my vehicles have coolant/oil heat exchangers which are a sandwich type unit that gets fed block coolant that fits between the oil filter housing and the filter, so it tempers the oil temperature as the oil leaves the pump, this is where the temp sensor is located, adjacent to this housing.

Oil does lots of cooling, my SRT has piston squirters which are used specifically to cool the undersides of the pistons, using oil. Oil cools the pushrods, rockers, lifters, camshaft, crankshaft, rods...etc.

My M5's oil cooler was designed to handle track duty, so while thermostatically controlled, the capacity of the oiling system and the engine's ability to reject heat, resulted in considerable seasonal differences in oil temperature under the same conditions.

Coolant/oil heat exchangers have become very common with the use of thinner oils, because they not only work to bring the oil up to temp much quicker (oil temp typically drags behind coolant temp by quite a bit), it also keeps it down under demanding conditions that would otherwise elevate temps beyond the capability of the lubricant viscosity-wise.

 

[FrogInTheWell]

Stick your hand out the window at 75 mph when it’s 30 below and tell me it’s not going to affect the bulk oil temperature, especially when the oil pan is exposed to the elements.

Arctic outflow takes on a whole new meaning when nature calls and it’s 42C below.

That's wind chill, Wind chill has no effect on inanimate objects.