What he said.

The engineer's only object is to meet the sweet spot between making the car run at optimum performance at lowest cost. If they could achieve that with lower octane fuel, they would.

There is no vested interest in making the car use more expensive fuel - in fact, if they could deliver the right performance and economy characteristics with a lower octane fuel and deliver lower running costs - they would!

With that said, the car does have the ability to retard timing to cope with a lower octane rated fuel. You will be duly rewarded with lower MPG and less performance.

The choice is yours - but my question would be, who buys a BMW and skimps on fuel?

__________________
2005 3.0d Sport - Sapphire Black
Engine : Bluefin Superchip Tune,
Wheels & Sus: Style 168s (10.5s all round), H&R RDA Spacers, Bilstein B12, Eibach 40mm drop, Whiteline RSB
Exterior: Le Mans flares, 4.6is kit F&R
Interior: Dynavin N6, Blackvue DR650 dash cams

My Build Thread: http://www.xoutpost.com/bmw-sav-foru...run-sheet.html