How we made our calculations
Five of the cars in our group have 50-litre capacity fuel tanks. Although some of the cars have 51, 53 or 55-litre tanks (one had 59), we only used 50-litres for our "Challenge." The range of these vehicles (Volkswagen City Golf, Mitsubishi Lancer, for example) would certainly be extended by their larger fuel tanks, had we started filled them to capacity.
Our technique to equalize the tanks was to fill all the tanks, then "drive off" the required number of litres based on the combined city/highway rating for litres/100 km as supplied by the manufacturer to Transport Canada. For instance, the Dodge Caliber has a 51-litre tank; the combined L/100 km rating is 8.24 which is equivalent to 12.1 kilometers. Consequently we "drove off" 12.1 km before starting the event in the Caliber. We used the same method for each of the vehicles with larger-capacity fuel tanks.
Note: We understand that our method is not scientifically defensible. In order to cover all possible factors that impact an event like this would be beyond our resources. In fact, Transport Canada uses a simulation to generate its ratings precisely because of the numerous factors that can affect results. We feel that we have used the same methodology for each of the vehicles, driven them on the same route on the same day, and offer our results with some certainty that they are representative, and accurate to a plus or minus two-percent margin of error.
.... I must say that I'm shocked .... reading your article really let me think that you guys really only had 50L per car ...
That is about the worst way to make this test accurate. I even wonder why you even considered using GPS to make the test more accurate when you totally destroyed any accuracy using such terrible technique to know that you should have "about" 50L gas in the car ....
Tank capacity and real capacity is totally different, all the plumbing can increase a tank capacity considerably, so you might think that this car only have 50L tank but you can actually fill 54L into it when it's 100% dry. Or it can have "air bubble" on top of the gas tank so you can't fill it full without insisting, continue filling even when the gas pump stop until all air bubble are out.
The way we'd like to be able to do this test is to run each car dry, fill them all with 50 litres from the same pump and then go again. Problem is that manufacturers usually supply cars with a full tank; give that we got most of them just a few days before the test, it would have been tough for the four of us who live in Ottawa (where we held this event) to drive the eight or nine cars with larger-than-50-litre tanks dry so that we could refill with the required 50 litres.
Then how can you know the car came with a full tank of regular gas?? If manufacturers fill them with supreme the car can do more mileage.
Next time you should simply use a manual gas pump (15$ value) to empty all the car then fill them with exactly 50L.
I agree. Though I don't think the results would have been significantly different in vehicle ranking, distances were probably within a +/- 25km range of error based on amount of fuel in the tank. However, as you have pointed out, it would have been easy enough to siphon the tanks dry, run them around the parking lot until they stalled, and then filled them with 50l.
The bigger concern is individual driving techniques. As an example, my wife seems to be incapable of coaxing more than 500km out of a full tank on the minivan. Yet, when I drove it for several weeks, I had no problem getting 600-700km on a full tank doing similar city driving (even though I'm a much heavier user of AC
). We simply have different driving styles. I'm 100% sure I could probably have made any of the vehicles achieve 100-200km better results. I know there was probably a pep talk to all drivers before starting, but there is no way driver behaviour for acceleration, slowing to a stop, etc... can be taken out of the equation unless it's the same drive who tested all the cars.
In the end, the test did show that on average, the Toyota and Honda surpass the competition in this area, it's a nice publicity stunt, but should not be taken as scientific fact. Buy the vehicle that meets your needs.
JB
