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[madtownrover]

Well, I have always understood that higher is better (no limit) with electronically managed engines that can set their ignition point dynamically. If youy put in higher octane fuel, the engine continually adjusts and fires later to just before knocking and hence gets more power out of it without knocking.

Is that a misconception?

Most vehicles will pull timing if octane is too low... I know of none that actually add timing if you run higher octane. You would need to have your electonics retuned for higher than 90 octane to benefit from, say 100 octane, fuel.

Unless LR has come up with some sort of magical ECU, there is no benefit, other than a big safety margin, to running more octane than you need for the particular driving task at hand.

My Audi has been tuned for 4 levels of octane. If I run 104 unleaded race fuel while the ECU is set for 91, I get absolutely no increase in performance. It provides a big safety margin, but at a very high cost. If I run 91 Octane while the ECU is set for 104 the car will pull lots of timing until it can't anymore...then it detonates.

 

[toddjb123]

... Then I put in 1/2 tank of 87 octane and significantly lost power, the engine noise increased, I started to see some hesitation. ....

I had thought that modern cars need a tank or two of full driving to adjust to any fuel changes. The computer will get used to your air/fuel combination and make adjustments.

Haven't tried this yet on the LR3 - be curious as it is a big price jump in my area from 87 to 91. (I hear ya though...is it worth it after you spend >$50K on a truck...still, be nice to test the fuel margins to see if if makes a difference after a couple tanks.)