TD200 Discovery thermostat

[Disco Gofer]

Hi guys. Can some one shed some light as to what the correct temp thermo that goes in my 1994 Disco 200 TDi auto?
I bought this rig 6 odd months ago and it's my first TD after 5 V8s. So I'm not sure where the temp should sit but this is how it goes.

It takes a good few km's to warm up , then around town and open road at 80-90 kph it's sits on a quarter. Go to 100 odd kph or on longer up hills still at 90 the it goes to half way between a quarter and half and on the off occasion to half if a hot day. When I tow my cruiser bush truck it sits at half on the straights at say 80-90 and on up hills (besides dropping to an embarrassing slow speed like 50 kph) it goes to 3/4 but no higher.

So it's not over heating but the question is then should I get a higher say 82deg thermo to keep the temp more constant?

I have googled the web to death and EVERY ONE including Landy Gurrus cannot agree what the correct thermo is. One says 76 the next 82 and then the next swears its a 88.........haha
I have fitted a new water pump, new coolant, refilled the viscous fan and they all check out fine.
I rode along in a friends manual 1992 Disco this week end open road and two days of off road Safari it sat on half all the time?

[LR90NZ]

Which of the several Discovery's were you in on the Pirongia safari?

According to parts manual correct thermostat is ERR2803 and it is a 88 degree thermostat.