Over the weekend I installed an oil temp sensor into a filter sandwich style adapter on my Explorer 2.3L. One of those plates that sits between the block and the filter that has NPT ports on it. Everything works and nothing leaks 
However, the oil temp readings seem really low. It was in the low/mid 20s this morning, and I drove about 30 mins to a customer’s home. Some interstate, but mostly 40+ mph roads. When cruising, even after 20 mins, the oil sat around 148F. If I stopped at a light, it would creep up to 160, but would come down again after I started moving at speed. The highest I saw it was around 172, while hot idling. The probe is very much in the path of oil flow, so it’s getting good fluid movement around it.
I find this surprising… this is a small turbocharged engine moving a large vehicle. Although the thermostat temp is 180F, I’d imagine the oil would get hot. The coolant also heats up very fast; up to full temp within 5/6 minutes usually, even when it’s cold out (I have a Scangauge for that).
I know that the reading at the filter might be slightly cooler than the sump, but I don’t think it would be that different. The first place the oil goes after the pump is the filter. From what I can see, there isn’t an oil cooler. Before I installed the sensor and gauge, I put the probe in a cup of hot water, and it seemed pretty accurate based on the temp I set my water heater to. The only thing I can think of is that the cold air coming thru the radiator might be cold-soaking the sensor. However, I doubt it. Once the engine heat soaks that would make the ambient temp irrelevant. Plus, I’ve read elsewhere that some people get higher temp readings at the filter compared to the sump
both the gauge and temp sensor are grounded directly to the negative battery terminal, FWIW.
However, the oil temp readings seem really low. It was in the low/mid 20s this morning, and I drove about 30 mins to a customer’s home. Some interstate, but mostly 40+ mph roads. When cruising, even after 20 mins, the oil sat around 148F. If I stopped at a light, it would creep up to 160, but would come down again after I started moving at speed. The highest I saw it was around 172, while hot idling. The probe is very much in the path of oil flow, so it’s getting good fluid movement around it. I find this surprising… this is a small turbocharged engine moving a large vehicle. Although the thermostat temp is 180F, I’d imagine the oil would get hot. The coolant also heats up very fast; up to full temp within 5/6 minutes usually, even when it’s cold out (I have a Scangauge for that).
I know that the reading at the filter might be slightly cooler than the sump, but I don’t think it would be that different. The first place the oil goes after the pump is the filter. From what I can see, there isn’t an oil cooler. Before I installed the sensor and gauge, I put the probe in a cup of hot water, and it seemed pretty accurate based on the temp I set my water heater to. The only thing I can think of is that the cold air coming thru the radiator might be cold-soaking the sensor. However, I doubt it. Once the engine heat soaks that would make the ambient temp irrelevant. Plus, I’ve read elsewhere that some people get higher temp readings at the filter compared to the sump
both the gauge and temp sensor are grounded directly to the negative battery terminal, FWIW.
