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.