Recently I have been driving the wife's car (Thor) due to a couple of minor issues it has had. I have noticed a big difference in the drivability between the Thor and my '97 Gems. The Thor is nimble , responsive and light on it's feet whereas my Gems feels heavy and sluggish. Also noticed that her Thor is about 3 MPG better on the jungle juice.

Is this typical or does my Gems need a spell on the Test book?

I have a '99 4.6 Thor, and had a '98 4.6 Gems. Although ownership was 3 years apart, from how I remembered the Gems, my current Thor is much more responsive, especially from a standing start. MPG wise, the Gems would give an average of 13.5 and the Thor is about 14.5. This is the average over 1000 miles or more as I just don't bother to reset the trip computer, and just fill the tank when it's empty. Not worth bothering about MPG on a car with a 4.6 V8, it's never gonna be good.

Thanks Alan. That's pretty much what I see. I just found it surprising that such a difference existed between two engines which are more or less the same. MPG wise the Thor averaged 19.6 over two brim to brim tanks of petrol whereas the Gems only managed 16.1. MPG. Both were measured over the same run.
I was thinking more about this last night after having read a post about resetting the gearbox ECU adaptive values and I realised that the gems changes up sooner than the Thor. Might take a closer look at the gearbox behavior and see if there are other differences.

I am not too surprised personally apart from the inlet differences between the two Engines. ECUs advanced quite a lot in the 1990s so quite feasible that the newer Bosch setup delivers better results.

The Thor is said to be down slightly on overall power but up on torque especially at lower revs compared to the Gems. More low down torque is exactly what the Range Rover needed. I'm actually a bit frightened to floor the throttle from a standing start too often in case I bugger the gearbox. I can easily beat the "tuned" Clio boys at the lights!

My low MPG figures are low as that's the average figure over thousands of miles, short journeys, trips to the shops, driving to/from work, longer trips etc, so are very real figures, but supplied by the on board computer.