My car is an 2000 OBW, with a 2.5L H4, recommended gasoline is just regular (87 octane). Now I've read in magazines and online that cars designed for regular can't really take advantage of higher octanes, so you shouldn't even bother to put higher octane fuel in, it's just a waste of money. Now cars designed for higher octane can take lower octane at the disadvantage of reduced power as the engine computer dials back the tuning to prevent knocks and pings. But cars with regular as their standard don't have computers that dial up their tuning.
So anyways, I decided to try out some super octane the other day. I filled half the gas tank with it (I already had a half-tank of regular already in there). I would say the average octane in there was a mid-grade 89 (half regular + half super). Then I took my regular long ride (200km). I tend to get 28 mpg usually on this ride, but I got 31 mpg this time. Now I wasn't doing anything differently than I usually do, I set to cruise to 125 km/h (around 80 mph).
Now just to avoid some confusion, when I talk about gallons, I'm talking about Canadian Imperial Gallons (4.5 litres), not US Gallons (3.75 litres). But the relative differences are easily understandable.
So why would this be the case? I've heard other people in other cars talk about this too.
Yousuf Khan