| I've been flamed for this before, but here goes :-)
In the past I have run my ML on 87, 89 & 91 octance. I have noticed no difference in performance or MPG, neither have I heard or detected any detonation (pinking) under heavy load or hard acceleration.
The engine control unit is doing it's thing and adjusting the timing as required for the various octanes etc.
For the past 20,000 miles or so the ML has been running on 89 octane with the very infrequent tankful of 91 as a 'treat'. So far so good....
Over in Europe high octane petrol is often considered a 'gimmick' and many people run on regular - so ignoring the 'recommendations' in the owners handbook.
I believe that high octane fuel is only really required for high performance turbo charged engines where the ECU 'may' not be able to re-act quick enough.
A lazy lumbering V8 as in an ML is more than catered for by means of the ECU.
FYI
I used to work for Ford Cosworth on F1 and Indy Car engine designing the ECU's for race purposes - so I figure I know when it's safe tp take an educated gamble. OK it's only a few bucks per tank full, but it's the principle ....
__________________
Tim (Formerly a senior race engineer / designer at Cosworth Racing UK for Formula 1 and CART engines)
'00 ML430
Replaced with Lexus RX400h 4x4 (0 to 60MPH in 6.5 seconds and 30MPG city)
My other 4x4 '03 Colbalt Blue Porsche Stage III 996 Twin Turbo (60 to 130MPH in 8.7 seconds and 12 MPG)
2005 Mini Cooper S, a pocket rocket
2002 VW Beetle, daily hack
Past cars of note:
'02 Porsche 996
'99 Porsche Boxster
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