If I run my gas tank empty I will fill the truck with mid grade because it hurts less.
If I am out of town and dont know how much premium the gas station sells I will buy regular because I know it will be fresh, I made the mistake once of buying premium at a gas station and it was stale, my truck ran, but she was not happy.
98% of the time I fill up when I'm at 3/4 tank and always use premium.

If I could get ethanol free 89 octane I'd use it exclusively.

 

Well I drove 8 hours all highway on 93 octane with ethanol and here was the breakdown on my two fills during the trip. Both on 93 next will try 89 ethanol free at least for one leg of trip when I go back and will report. Numbers were close both tanks too.

July 15th
96,797 miles got 316 out of full tank filling when gas light came on filled 21.68gal averaged 14.57MPG all highway. Would have thought more lol.

July 15th
97,041 miles got 244 miles filling around 1/4 tank put in 17.11 gal averaged 14.26MPG all highway.

Now for the bad part pulling my two jetskis back.
97,305 miles got 264 mi filled when light was on 22.57 gal averaged 11.7MPG

All of these were with 93 Premium with Ethanol averaging $77-83 to fill. Being the pump for 89 ethanol free is around the corner from my house and is $3.49 a gal Im going with it next fill.

 

I underlined "CLC" and "AKI" in your quote above.... These are two different ways of calculating and indicating octane levels in fuel etc. One method is used in Europe and a lot of other places and the other is used here in the States and everywhere else.

They are not interchangable measurements. It's like yards and meters. Similar measurements in length but not close enough to used interchangibly etc.

The point is "CLC octane 90" and "AKI octane 92" are the same octanes measured with different units. So "AKI 89" is not "just one octane point away" or different from "CLC 90". AKI 89 is about 2 or 3 AKI octane points away from CLC 90.

My opinion is that the long and short term health and drivability of your Disco requires that you use premium fuel with CLC/AKI octane levels as stated in the owners manual.

However, if you were Washington instead of Florida, and because I get so many cheap and excellent parts for scrapped Discos in local junkyards, I'd encourage you to use low grade 87. (that's a joke of course. there's enough Disco owners, who don't love their Disco enough to visit this forum etc, running 87 and 89 octane fuel to keep me well stocked in parts.)

cheers,

thomas

 

Speaking of hurts less, I'm going to have to start keeping my disco pretty full now too. After the 3 inch lift and 33's I've noticed that it rubs going into the garage if the tank is close to empty!

 

LOL!!!
I have a similar problem, the @ss of my truck gets "loose" in the snow/rain if it is below half because of my ARB bumper.

 

My rover never fit in the garage.

I don't worry much about the mpg in the truck anymore. The checkbook has been feeling the pain of the boats fuel consumption. Been going thru about 200-260 gal of non-ethanol 90 oct every weekend.