>And my aviation point was also wrong, as the aircraft have to take-off at >sea level!

Oh yea, I didn't even think of that. Performance at take-off is probably a serious issue :-)

>harm at high throttle openings. I also can't see that having differing >fuel specs all over the place is in any way a good thing, or easy to >administer, or even cheaper having non-standard mixes.

From the POV of the octane, if it was cheaper to make it all the same, you can be sure the oil companies would be doing just that. It must be cheaper to be 'elevation sensitive' or they wouldn't put up with it.

There are many other additives that differ from state to state, so maybe the octane isn't that big a deal to them. <shrug>

>Octane ratings >higher than the minimum required don't actually do damage to an engine,

Until I was recently proven to be wrong by a someone's technician, I had been taught by the gasoline companies I worked for, that lower octane is cheaper, so wherever it provides the same performance, it is used. Lower elevations require higher octane, which costs more to produce. If the oil companies had their choice, the whole country would get 85 as the low end, but since that doesn't work, they put the 85 octane in all the places that it will perform correctly. Higher elevations.

>The DJ needs 93 minimum at Sea level. It runs a 10.5:1 CR as standard >from the factory. It goes better with 98, Super Unleaded and does another >mpg maybe.

If everything is up to spec, you won't see any difference between 93 and 98 octane as far as performance and mpg are concerned. Octane has nothing to do with either of those factors. The Super Unleaded probably has other additives that affect the performance.

Interesting day here in Vanagonville, ain't it? :-)

John