Fuel economy experiment

As almost guaranteed by the fact that I said I would, I ended up not blogging at all on the trip to PEI.  It was great, of course, but we were so busy I hardly had time to check my e-mail, or the few Twitter messages that get delivered to my nonsmartphone.  I have a huge folder of pics to go through and post up on my Flickr account, which I have yet to do.  One thing I did do is keep track of our gas mileage on the trip.

I’ve been keeping track of my mileage since I’ve owned a car, back in 2003 when I bought my first car.  You see, doing things like saving small bits of paper and entering numbers into spreadsheets is pretty much as exciting as life gets for an accountant, until you get around to actually making a graph – that’s like Christmas.  It’s been interesting to me to see how my driving style affects my mileage, and to rate myself against government fuel economy ratings.  On this trip, with Tay having barely learned to drive the car before we left, I had the opportunity to compare myself with another person driving the same car.

First off, the car.  We drive a 2002 Ford Focus sedan, with the high-performance Zetec 2-litre 16-valve 4-cylinder motor mated to a 5-speed manual transaxle.  The EPA website gives this car a rating of 10.7 L/100km city, 7.6L/100km highway (22/31 mpg).  Supposedly the automatic model gets better mileage; I call bullshit.  Keep in mind my air conditioner is broken, so we don’t waste gas using it.

Here’s where we get to our “experiment”.  After the fact, and without having thought of it beforehand, I decided to compare my driving to Tay’s over the course of the trip, in terms of fuel economy and what I’ll call “time economy”.  More on that later.

I was a truck driver in a past career, and am comfortable with driving for long stretches without stopping, so I drove for about 4-6 hours at a time.  I’ve developed a style of driving a constant speed and using cruise control, and drove with it set at a reasonable speed, except when passing, and in hilly areas where I let the car slow down on the uphill and use gravity to accelerate on the downhill.  Twice on the trip I drove from one gas station to the next.  On those tanks we scored an impressive 6.8L/100km (41 mpg), but we’ll say my average was 7L/100km.

Tay, on the other hand, doesn’t really enjoy driving for long periods, and was hell-bent on getting to the next stop.  She drove for 2-3 hours or so at a time, didn’t use cruise control, and drove … let’s just say she drove faster than I did.  Although she didn’t last for an entire fuel-stop-to-fuel-stop leg of the trip, our combined mileage rose to about 8.5L/100km, a 25% increase.  Since that’s about a 50/50 split between the two of us, we can assume that her mileage was even worse, let’s say 40% worse – a conservative estimate apparently.  We’ll say her mileage was closer to 9.5L/100km (30 mpg).  How she drove turned out to be closer to the EPA’s estimate, but I have yet to explain why I think that’s bullshit.

Here’s the fun part!  Since crunching all that info into my spreadsheet, and seeing the difference in our mileage, I thought it would be interesting to figure out which is the more time-economic style of driving.  It’s obvious that my driving is less expensive than Tay’s, but which one actually gets us there in less time?  Here comes the math, and I won’t be giving imperial conversions in the next section.

Our drive from Charlottetown to Toronto gives better numbers, because we filled the car just outside of both cities.  The drive was 1,617km, and we used 122.3L of gasoline which cost $119.21 to replace.  We’ll assume that we can use 40L of gas between fillups, and that a fillup includes a pit stop and takes 30 minutes (more realistic than you think).  If I drive, we can go 571km between fillups in 4h45m.  We need to fill up 3 times, and the trip takes just shy of 15 hours.  If Tay drives, we can go 421km to a tank in 3 hours.  We need to gas up one extra time, and the trip takes 13.5 hours, a full 90 minutes faster.  At our average cost of 97.5 cents per litre, I’ve spent $107.25 ($7.15/h) and Tay has spent $149.76 ($11.09/h).

It turns out that driving faster does make the trip shorter, but you definitely pay for it.  Honestly I was expecting there to be more of a difference in cost and in time, and I’m not going to be changing my habits any time soon.  Drive safe!

IMPORTANT NOTE: I am not suggesting that you should drive above the speed limit on any public or private road, anywhere, at any time, ever.  Speeding is both dangerous and illegal – you could lose your car, your license, your life.  Please be careful and always drive safe.

About Greg Burrell

Greg is an accountant, cyclist and political observer living in Toronto, Canada with too many cats.
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