Ok, I got a lot of differing views on this from members of the Cavalier/Sunfire club I belong to, and while these guys know a lot about cars and in some cases work on them, none of them have ever owned or even worked on a Discovery, much less anything built by Land Rover, so I'm not sure if I should stick with their opinions. So I'll ask here. What octane gas should I be putting in my Discovery? The engine's the 3.9 V8, has 80,000+ miles on it, has spent half the time in the shop ever since my folks got it a year ago, and the acceleration has a very noticable drop whenever it's running on less than 89 octane gas.

mate, use your nut, I recently purchased a 98 Disco 3.9 V8. First thing you do when driving off the dealers yard is fill it up cos the dealers to tight to do it. You use the cheapest which is 91 octane here in NZ. Guess what, for the next week my new baby was 'pinking' like crazy. Next fill was with 96 octane and presto no 'pinking' , more power, smoother. Cheers mate, and happy grunting.

89 !!!!!!!
Jeeees, put some proper petrol in it.
The standard here in the UK is 95 or if ya wallet's overflowing you can squirt in 98.