https://www.ebay.co.uk/itm/223102658493

This supplier can sell different size oil drain plugs if you wanted to measure temp from that location.

That`s good value, well spotted.

Mezo.

I got one of these on a whim during the first UK lockdown last year and replaced the engine oil drain plug on my 34L with the supplied sensor. On a warm day (30c) the temp displays 80 to 90C when stationary. On a 20c day it's generally around 70 to 80c stationary. It drops 5 to 10c when cruising. I've since removed the PCB from the flimsy case and mounted it in an empty xt Speedo case I had lying around.
The voltmeter works great too.

https://www.ebay.co.uk/itm/143569639976

Something like this would be better in between oil pipe and oil cooler. DR650 oil pipe flange bolts are 30mm apart. May work in this application. I would always recommend to have a quality magnetic sump plug in these bikes so wouldnt lose that for an oil temp guage..

https://adventurebikeaustralia.com.au/p ... mp-sensor/

and use one of these with it

https://www.mxstore.com.au/p/Trail-Tech ... FkEALw_wcB