You let your wife speak out of turn about your Rover??? Shame on you!

 

Engine runs hotter, bad things happen... etc...

 

First, I must disagree with some of the info so far:

Read:

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Octane rating - Wikipedia, the free encyclopedia :

Octane is a hydrocarbon liquid which is used as a reference standard to describe the tendency of Gasoline, Petrol, or Benzin fuels to self ignite during compression prior to the desired position of the piston in the cylinder as appropriate for valve and ignition timing. The problem of premature ignition is referred to as pre-ignition and also as engine knock, which is a sound that is made when the fuel ignites too early in the compression stroke.
Severe knock causes severe engine damage, such as broken connecting rods, melted pistons, melted or broken valves and other components. The Octane rating is a measure of how likely a gasoline or liquid petroleum fuel is to self ignite. The higher the number, the less likely an engine is to pre-ignite and suffer damage.
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Engine damage: our Bosch Injected engines have knock sensors that will reduce the timing advance if it picks up evidence of pre-ignition (knocking). Bosch has gotten very good at this system, and it has been used on a huge number of different cars from Lambos to Volvos. I run a Porsche 944 Turbo racecar which has almost the exact same injection system as our Discos. At normal boost levels, I can run the 87 safely; but I lose a bunch of power as the timing is retarded. So, that is why I do use 100 octane leaded

Power: I have never used anything but 93 in my Disco, so I cannot tell you if it even uses enough timing advance to get knocks, but if it does, you will leave power on the table if you use lower octane fuel - see above.

Gas Mileage: This part might be true, you might lose MPG's if you go with lower octane. Again, the higher the octane, the more advanced the ignition timing can be, and the more effecient the engine can become. That said, MPM (miles per money) stays roughly the same in my experience. Many years ago I did a test with my Porsche 928. It again has the same fuel injection system as ours, and even has a V8. For 6 months I ran 89 (the lowest where I was), and then 6 month I ran 95 (the highest where I was). Yes, the 95 gave me more MPG's, but when you factored in the additional cost, it was almost perfectly equal. I am sure that I would not have nearly the same power, but I purposely ran both tests with a "normal" right foot.

Now saying all that, I USE 93. It works out roughly the same price, you can usually produce more power, and hey, the cars' designers told us to . . .

 

Personally, i think this should be the answer you should give her..... She'll understand this real quick.

 

Now this response is for us men only and I'm not saying that all Disco's would have this same result.

Upon purchase of my 04' disco new in 04' I can remember like it was yesterday us asking if we needed to run High Octane fuel. The answer was no and we didn't run High Octane for the 7 years following. I just completed a complete engine rebuild for lose of oil pressure with the cause being a failing oil pump. In review of the engine components involved in fuel burn contact ie. pistons, valves, head chambers I saw no evidence that the low octane fuel caused any damage whatsoever to the engine.

We had no issues with detonation or ping ever with the Disco and never got any check engine lights. The Milage as we all know is not good to begin with so I was never concerned about this.

All that rigamaro being said on this new $4500.00 rebuild I will be running High Octane for what I'm not exactly sure???

 

I will side with RPI on this...

"4.0 & 4.6 (new shape) suffer a similar but normally less dramatic problem although these engines are much stronger. The same air/fuel ratio problem will arise with low octane fuels, you will not normally suffer cracked blocks, but you will cause the liner to shift from its seat or cause sticky valve guides"

So run whatever you want and ignore the manufactures recommended octane, it's your truck not mine. Good luck to you. Mine has always run premium and had it's regular oil changes. It still runs like a top and doesn't burn a drop of oil. It has never been rebuilt and has 128k on it. No sludge at all. YMMV.

 

FWIW, I have found that when I run 94 octane, I am able to get low-mid 13 MPG. 91 octane gives low-mid 12MPG, both with 90% city driving. I have yet to do a cost per gallon per MPG calculation. There is only one station that sells 94 octane in my town, and it's not on my usual route to and from work, so I use it only so often.

 

Well here is my $.02, I'm the second owner of my truck, the previous owner always ran premium fuel, I have always ran premium fuel.
My truck has 205,000 miles on the original engine with nothing ever being done to it other than tune ups and oil changes, original head gaskets too.
Land Rover says to use premium.

 

Yeah but you have a badass rugged D1.

 

I still dont understand why anyone would ever buy a DII without a TD5.
Thats the only way I'd buy one.
If my truck were to get crushed by a tree I'd buy a Series and a $500 Camry with the insurance check.