Originally Posted by Focus YBTC
For years most cars did not gain a performance increase by burning high octane fuel mostly because they had relatively low combustion chamber compression ratios but they also lacked proper fuel injection and electronics to manage the engine in that regard. The experts told people truthfully that premium gasoline offered no performance difference and poor value in these engines in light of that. More advanced modern cars with high compression ratio engines like in the 2012 Focus
(12.0:1) that can manipulate ignition timing and other things automatically to take advantage of premium fuel are a different story. At any rate any Focus owner can safely use either octane gasoline at their own preference.
Since we don't have a proper test done to confirm power or economy increases with the stuff I may as well offer my anecdotal high octane story as well. I filled my car up with BP premium a few weeks ago, reset the odo and MPG meter etc. and didn't notice any significant changes. When the fuel was halfway gone I refilled with premium again from a Shell station. Filling up showed MPG had gone up a bit over the last one (around 1.3 MPG ) and the engine seemed a bit stronger but nothing dramatic.
Last week I was driving to the airport and reset everything to see how far the airport was. I was surprised that the 38 mile trip produced 39.1 MPG on a 48 degree morning. The return (more uphill) trip today when it was warm (mid 80s F) left off at 40.2 MPG over around 80 miles which is the highest MPG average I've seen yet in my just over 1000 mile old car. Granted that's driving moderately on a mix of 45-55 and 70 MPH roads and not really hammering the car but still pretty impressive. Just as importantly the car is now running better too, a tad more low RPM torque and noticeably stronger power as you wind it up higher. I didn't hammer it but I did do adequate testing to determine this.
BTW, I was all over San Diego County CA this week and saw very few 2012 Focuses (less than 10 total over 5 days) and not one
of them were hatchbacks. I thought that was kinda weird.
I'd be surprised if I didn't have a similar experience.
Just today I did over 100km of driving. I swear the indicated range left dropped only 50km. same driving style as always.
The first thing I noticed about the engine was the high compression ratio, figured of nothing else the engine should run better with better juice, only time will tell if the economy really improves.