Whitehorse to Mayo & Return on one tank of gas (821 km)

I had some work last week up in Mayo drilling a couple of new water supply wells for the town.  Over the past couple of years I've gotten interested in "eco-driving" - that is modifying my driving behaviour to maximize fuel efficiency.  So, I decided to see if I could make 1000km on one tank of gas.  I didn't quite make that, but I did get to Mayo and back on 66L of gas.  I turns out my car has an 80L tank, but that includes a 12 L "reserve", so it tells you are empty at 68L used.

And no, I don't drive a Prius or a Fit - it's my big old German tank - a 1991 Audi turbo quattro - a big all-wheel drive sedan.  Not bad eh?

So, how did I get this far on one tank?

Here is the secret: I drove the speed limit.

Yup, that's pretty much it.  Imagine if everyone drove the speed limit - we could probably reduce vehicle fuel usage in the Yukon by 20%!  Ok, I had a couple of other "hypermileing" tricks, but I don't know how much of a difference they made:

• light load (just me in the car)
• coasting down big hills with the clutch depressed
• very slow acceleration
• shift up early (5th gear as low as 60km/hr)
• NEVER touch the brakes if you can avoid it
• no radio or other electrical loads

Another interesting thing is I had a really good tailwind going north to Mayo.  I averaged about 31 mpg on the way up.  On the way back to Whitehorse, there was almost no wind (or even a slight headwind), and my mileage was much lower - 28 mpg.  Interesting that the wind could make a 10% difference, even for a low-drag car such as mine.

David MacKay has a nice summary of the effect of speed on fuel efficiency of a car in his excellent book "Sustainable Energy - without the hot air".