High fuel economy question

[Pitts]

So after reading several threads on highway fuel economy, it seems people tend to get 25-29 mph. I know ZBum commented on several of them. I'm just curious why I get 30 mpg when driving in the good ol Rocky Mountains (with dangerous passes that claim lives in the winter) when I weigh 230lbs and I've got 100-175lbs in the hatch. When my hatch is empty and I'm on a straight away on the plains a few hours away, I get 34-36 mpg. I'm not complaining one bit. Just curious as to why my MPG is so high. I know quality of gas is a factor and I always run 91. I did talk to one guy from Alberta a week ago and he said that his fuel economy increased on his Honda Goldwing by 17%. My elevation is about 5700 feet above sea level.

[ezb57e]

Octane rating relates only to the temperature at which a fuel will ignite, and has no direct correlation to efficiency or increased mileage. Unless an engine has high compression or other characteristics that create high temps, high octane ratings are wasted.
However, high octane fuels also tend to be the makers top tier products, and may contain other additives that benefit engine performance.
Beyond that, I would be sure about my math in MPG calculations.
Is your tire size stock?

[Pitts]

Stock tire size. I verified my mpg on a full tank (and refilled after to get an accurate gas consumption) and distance with both my odometer and GPS.

[G-E]

What makes power is advanced timing, which benefits from high octane fuel...

It is very possible to get >30mpg with premium, but since you pay a premium, you likely haven't gained a thing in your pocket.

You should measure distance per dollar

[Pitts]

My timing is at 15 degrees for ignition. I'd expect 1 or 2 mpg on premium fuel, but not that big of a difference. Although it's unlikely, do you think that our quality of fuel might actually be better?

[G-E]

It's very possible the fuel you got has a higher specific energy, for example ethanol has about 25% less specific energy to gasonline, therefore any ethanol blended fuel will provide less power than the equivalent octane pure gasoline (yes I know even that's a blend, heptane, iso-octane etc)

[Aegis156]

Simple answer is your driving habits. Straight line commute (cruise set at 70 constant RPM) will see higher MPG than bombing around town constantly shifting with high RPM shift points. on long trips I normally see MPGs in the mid 30s, dropping into the 20s when I get silly in town. Every car has two MPG ratings one for highway one for local.

[Pitts]

Yes Aegis, but there also many other variables that come into play (such as plug condition, cap and rotor condition, injector condition, etc).

Ezb57e, a month later I moved. Went 60 behind the UHaul except when we were in the canyons (2 empty lanes, mostly down hill, tons of turns), kinda hard to control the throttle there. Haha. But I managed to get just a hair under 40 mph. Fueled up right at the on/offf ramp and fueled up right at the on/off ramp at the new town. Verified the distance with 3 different odometers. I also am not the kind of person who babies the car. Its WOT whenever I can.