These days, when discussing fueling during pit stops, teams talk about things like head pressure and flow rates. It’s all fancy terminology used to describe how teams can get the fuel out of the cans and into the cars faster. What teams discovered, is that filling cans as full as possible allows the fuel to flow faster from them. But when cans get filled at the Sunoco stations at the track, they aren’t filled to capacity. The Sunoco workers put approximately the same amount of fuel in each can, which leaves a little extra space. Crew members were then taking these cans to pit road, and adding extra fuel to them from storage cans.
In doing so, and getting better flow rates from the cans, teams can have faster pit stops and get cars fuller, which creates a competitive advantage. Especially at tracks where tires aren’t an important factor, like Daytona and Talladega. Having cans that dump faster allows fuel only stops to be quicker, the now popular two tire/two can stops to be quicker, and for cars to be completely full on standard four tire stops.
Some teams have been getting away with this all season, but in recent weeks NASCAR has become vigilant in their efforts to stop the practice. Officials have been walking pit road during the race and forcing teams to remove extra storage cans from pit stalls. There was not a rule in the rule book prohibiting it per se, but NASCAR has been letting teams know all season they didn’t want it to happen. Now this bulletin makes it official.