Originally Posted by Spike555

Running the wrong fuel octane will not cause carbon build up on the valves, all it will do is cause the ECU to retard the engine timing because the Disco was designed to be ran on 91 octane or higher motor fuel.
It also will not cause lower MPG, because the ECU will retard the engine timing to compensate for the lower octane fuel.
You may notice reduced MPG or engine performance while towing heavy loads or at high speeds.



These engines are computer controlled and fuel injected, which means the ECU controls how much fuel the engine gets, and it will only give it as much fuel as it needs.
The ECU will also use the knock sensors to adjust the ignition timing to keep the engine running at optimum efficiency and performance.
You will however get carbon buildup if you are running worn out spark plugs and or spark plug wires because weal spark will not burn the fuel/air mixture correctly.

My experience with E-85 in a non E-85 car, it kills the fuel pump and fuel injectors.
In my Carmy it killed the fuel pump, in the Volvo it killed the fuel pump and fuel injectors.
It will also set off the check engine light because it runs to lean and the O2's will read that its running to lean and they will throw a fault code.

Your best bet is to use the fuel that is recommend by the manufacture and stick with that unless its a emergency, then use whatever you can get.