I just returned from a 2400 mile trip and noticed a strange occurance.
I live near sea level (Seattle) and get about 12mpg driving around town and short freeway trips.

While on vacation (Yellowstone) we were driving between 7000 and 9000 feet in elevation, I got considerably better mileage (14-16mpg) driving around the park.

What do I need to change so that I could see that mpg here at home?

 

My guess is there is nothing you can do. At sea level the air is more dense then 7000 to 9000 above sea level. With the air being more dense it takes more fuel to get the proper air to fuel ratio. Where as the thiner air requires less fuel to get that same level.

 

The cure = drive more.

Short trips = bad.

Amazing that 1200 miles to the park helped so soon, no?

The altitude, while a factor, probably made little difference in the end as the computer adjusted to it with ease.

 

I am no Rocket Scientist...but that cannot be right. But then again, running lean=higher mpg's. I guess you are right since he had to be running lean, and rich=faster.

 

I have noticed this phenomenon too. I live in Louisiana (essentially sea level), but I love to vacation in the Colorado mountains. I have noticed an increase in gas mileage while there, which at first thought seems to defy logic.

However, I developed a theory that it is not so much the elevation as it is the "uphill and downhill" aspect of mountainous driving. This idea first occurred to me when I rented a vehicle with a trip computer with mpg display on the big island in Hawaii. We drove it to the top of Mauna Kea, sea level to 13700 feet. The vehicle was averaging around 16 mpg on level terrain, and dropped to 6-8 mpg climbing the mountain, which was what I expected. Coming down the mountain, however the mileage at times went as high as 99.9 mpg, which was the maximum reading of the display...essentially the mpg went to infinity, compared to driving uphill or on level terrain.

In other words, if you drive up a grade, the decrease in mpg might not be as great as the increase in mpg when you come down the same grade, particularly if the grade is one you can coast down with no throttle, i.e under mild to moderate engine braking.

I think that under the right conditons, such very high manifold vacuum due to engine braking, the engine computer on a modern fuel-injected vehicle can temporarily shut off fuel flow to the injectors completely. No fuel flow at all while moving = infinite mpg.

Just a theory...

 

Actually, the thinner air is the reason. But not because of causing a lean condition as much as decreased air resistance. You arent pushing as much air as you drive. It works the same for aircraft, the higher they fly, the more fuel efficient they are.

 

While driving around yellowstone, you encounter a lot of stop and go driving while everyone stops to look at animals, I don't know if we made it 10 miles in the park without having to stop.

All I can say is that whatever the cause is, I didn't mind with the price of gas.

 

Is it possible the amount of Ethanol in the fuel is different there than it is back at home. I know that crap sure doesn't help my mileage.

 

How did you enjoy your trip? Last summer I went to yellowstone and we went out on yellowstone lake for a guided fishing trip.. that was by far the most memorable thing ever and something I will always cherish experiencing with my dad. We went the whole trip my main thing was to see a grizzly you know.. and we were leaving on the last day I was bummed.. we were heading from west to south entrance of the park @ 6:00 AM and we passed a little picnic area (ironic?) and my dad said "I think I just saw a bear".. haha I was like TURN AROUND!!! dude we saw this young grizzly (prob a teenager) rummaging around the picnic area.. was so amazing. I want to go back so bad... so did you stay in hotel, cabin, tent?

 

The trip was amazing, we stayed at Madison Campground in our trailer.
Worse part of the trip was the snow storm.
Saw 90% of the animals in the park, including grizzly.
There is nothing that tells you that you are in the wild then walking back from fishing and following a bison into the campground.