Engine oil running cool. 50C on the motorway, 60C on track.

[CrutyRammers]

I fitted one to the sum plug like you OP, and I seem to be having the same trouble. On the rolling road yesterday it didn't read above 65 degrees, so the sensor is presumably not actually getting into the oil.
Into one of the oil lines sounds more likely to work, but is going to be a pig to fit.

[Mojocvh]

Thermostat. Lazy ie failing open?

[nsa]

CrutyRammers said:

I fitted one to the sum plug like you OP, and I seem to be having the same trouble. On the rolling road yesterday it didn't read above 65 degrees, so the sensor is presumably not actually getting into the oil.
Into one of the oil lines sounds more likely to work, but is going to be a pig to fit.

If the thermostat is working correctly oil shouldn't circulate into the oil cooler lines until it reaches 95C, so any temp taken before then will be roughly ambient.

Mojocvh: I'm fitting a new thermostat this weekend.