Fiat on the Beach

How to Guzzle More Gas

Speed Affects Fuel Economy

(aka: How to Guzzle More Gas)

Driving fast can cost you a LOT of money in extra gas used. Here’s proof…

This is something anyone can try at home, and I encourage you to do so because it’s quite an eye opener!

The theory: I’ve read on several “fuel-savings tips” lists that increasing your speed can cut your fuel economy by something like a third.

The scenario: There are two main routes to get from where I live in Comox (BC) to Campbell River. One is the “Old Island Highway”, with a speed limit of 80 km/hr. The other is the new “Inland Island Highway” with a speed limit of 110 km/hr (note: after my experiments this limit been updated to 120 km/hr).

The experiment: We will drive from Comox to Campbell River and back once using the old highway, and once using the new highway, and will check the fuel used and time it takes. (We also had other reasons to be in Campbell River, of course). At both times we will fill up before and after the trip using the same pump at the same gas station in Comox (the Co-op), resetting the trip odometer before each trip and checking the distance at the end of each trip. And in both cases I drove at the speed limit whenever possible.

The Results:

1) Time:

Using the Old Island Highway (at 80 km/hr), we got to Campbell River in 44 minutes.

Using the New Inland Island Highway (at 110 km/hr), we got to Campbell River in 47 minutes.

2) Cost:

Old Highway = $8.25

New Highway = $12.77   (fuel cost per liter was the same for both trips)

3) Fuel used / Distance:

Old Highway = 7.3 liters for 96.5 kms

New Highway = 11.3 liters for 120.2 kms

4) Fuel Economy:

Old Highway = 7.5 liters per 100 km

New Highway = 9.4 liters per 100 km

30% more gas used? Is this for real?

The Conclusion:

It does indeed cost more to drive at higher speeds. In our test here it cost us nearly 30% extra fuel used per km to drive at 110 km/hr instead of 80 km/hr.

It would be illegal for us to test this, but just imagine what speeding over 110 km/hr will do to your fuel economy!

In real dollars, this means that someone commuting from Comox to Campbell River 5 times per week (in a similar vehicle) can save $23 per week or about $1100 per year just by using the Old Island Highway! You may have a similar choice of roads where you live, but even if you don’t, just slowing down can save you $30 for every $100 of fuel you’d spend at 80 km/hr.

Some details to keep in mind:

* The route to get to the New Highway involves a fair bit of driving at lower speeds, so the actual fuel economy at 110 km/hr is likely worse than shown. (And that will be even worse at the new speed limit of 120Km/hr)

* Both highways were quite calm in terms of traffic, so we were able to maintain the speed limit easily for these tests.

* We used cruise control on the New Highway to stay at 110 km/hr. We did not use cruise control on the Old Highway. In theory, cruise control should help to improve fuel economy.

* For these tests, we used a 2000 VW New Beetle, with the 1.8 liter turbo engine and automatic transmission, using premium gasoline.

* Vehicles such as trucks and SUVs with larger fronts will likely have more wind resistance and will therefore benefit even further at lower speed.

* The price of gas was at $1.13 per liter when this experiment was done. Higher prices will mean even greater savings.


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