View Full Version : +Octane = +fuel economy?

03-03-2005, 11:41 PM
So, after careful(ish) calculations, I've concluded that here in Maryland 93 octane costs approximately 12% more than 87 octane. My question is then, if the engine runs more efficiently on higher octane (assuming that timing is advanced in order to take advantage of the improved octane), is there anyway I could see a 12% increase in fuel economy?

Oops... I should have clarified, the vehicle in question is an '05 Focus w/ 2.0 liter (5-speed) and I generally get 30-31 mpg... I'd need to see 34 or 35 to break even (not counting the cost of the chip or whatever was needed to advance the timing).

is 60 points significant enough to make that kind of a difference?


03-04-2005, 12:01 AM
Higher octane means lower MPG because the higher octane has less BTU per gallon.

MIKE 38sc
03-04-2005, 01:50 AM
Higher octane in the Focus is a waste of money and will result in lower fuel mileage because that engine is low compression and not set up for high octane. The SC engine is higher compession because of the blower boost and thus set up for high octane fuel. Using low octane in a SC engine will result in lower mileage and possable engine damage.