Oil Temperature Sensor Accuracy

[the machine]

Have been paying careful attention to the oil temp during warm-up and wondered if anyone else had experienced similar.... I keep the revs below about 2500 until 40degC, but have noticed that when cruising the oil temp can actually start to go down..

This happened when driving home last night. Got up to about 36degC before i reached the motorway, then i started crusing steadily at about 2400rpm - the temp gradually went down to 34degC. It stayed there for about 5 minutes until i slowed down for a roundabout and lights and then shot up to 45degC in a matter of a seconds.

Is this just a result of incoming air affecting the sensor when driving at speed, or is it a true cooling affect on the engine and oil temp?
I cant believe that the engine doesnt continue to warm up when crusing steadily at around 2500rpm, regardless of what speed your doing - does it imply its better to leave the car in the garage and sit idling because the oil warms up faster?

Any advice appreciated.

[astonman]

I would avoid idling at all costs to avoid cam wear problems,I always warm mine up at 2-2500, but as it is only used in the summer I have no experience of the cold! However oil temperature normally follows water temperature, so if the water is hot,then after a while the oil should be hot.This doesnt happen if you have an oilcooler without a stat,but It should happen on a standard car,so I suspect the sensor.simon

[grumbledoak]

Worry not! The oil sensor is quite open to air-flow, and will show a (false) drop at motorway speeds.

[the machine]

Thanks- that's put my mind at ease about a 'dodgy' sensor.

[holmsie]

I've asked this question a few times before as well to various people and never really got a conclusive answer.
Although, having driven the car over 2 winters and heading for a third, it's become pretty apparent that it's just the sensor being affected by cold air. As you've seen, when you pull up, the oil temperature will climb quickly, and if you look at your oil pressure you should notice it'll be at full temp pressure.

[Lensey]

I noticed this with my OPS, it started reading rubbish a few weeks back so I put a new one on, all reading ok and it still reads cooler when on A or M roads.

[YI8TVR]

The OTS is located 3/4 down the oil reservoir tank on the drivers side. You can see it through the front off side wheel. To overcome the winter read outs you can wrap the reservoir tank with quilted foil and cable ties. This will give you a truer reading

As you can see I fitted a mechanical OTS and reads colder in winter, so it may not necessarily be a faulty electrial OTS

Edited by YI8TVR on Tuesday 23 October 12:04

Edited by YI8TVR on Tuesday 23 October 12:07

Edited by YI8TVR on Tuesday 23 October 12:08