re: oil change intervals
I used to have a series 1 Disco, and of course the topic of oils & intervals was a popular one on one of the Land Rover forums; one of the guys was an LR tech who had an interesting viewpoint on change intervals - at least as it was related to the early Discos: every 3k or every 3 months, whichever comes first, and run a can of ATF (automatic transmission fluid) through it for 5 minutes in the driveway (i.e., no load on the motor, just idling) prior to the oil change. Didn't matter what flavor oil, just use the right viscosity (obviously).
And since I was only putting about 2500 miles/year on my truck at that point (I'm a motorcyclist) I practically spit my coffee over the monitor. 4x a year, for 2500m? In the summer, I would go 2 months without even putting GAS in that thing (because I'd have put 4k on one of the bikes), nevermind changing the oil ...
But ultimately, apples to oranges: that was a Rover, my T4R is not ... and the Rover barely made it to 100k, whereas I'm looking at 201k ...
Regarding the 4R, I'm still trying to decide whether to swap up to full-syn and/or 'high mileage' ...