Do we need the high test in a 03Disco?
I find 87, 89, 92. Is the 89 good enough?
The OM calls for 90+

 

Because of it's high-compression and push rod design, yes, you should really be running high test.

 

If you search the forum you'll find lots of discussion on this subject.
The quick summary, if you use lower than 90, you might save some $$ up front, but your mileage will suffer and you risk fouling different sensors and components. Take the hit up front and use premium.
others will say you can use lower octane, but the "gurus" on the site will advise otherwise,

I trust the old guys on top of the mountain
(prolly cause their disco is running well enough to get them there)

 

You knew the answer before you asked.
If you don't run the highest octane gas you are just asking for worse gas mileage, carbon build up, lifter damage, I could go on and on.
Mike

 

I jusrremembered that the minimumgas pumpoctane rating in the UK is 95, so I'm sure the LR engineers didn't really plan on the engine having to make do with 91 octane at best. They probably designed the engine around being optimal with 95 octane. I think premium is 97 in the UK from whatI can remember?

 

UK 95 is not the same as US 95.

 

i ran one partial tank of mediun grade gas for the heck of it, yep they recommend it for a reason, had a caddy a few years ago and they take high test too. i wouldn't even try running less than premium!