Some Thoughts On Gas Mileage and NASCAR
Over the course of a season, you’ll often see races come down to what’s known as a “fuel mileage” race where, depending on how the cautions fall during the latter stages of the event, teams will find that their in-car fuel supply may or may not be enough to get them to the checkered flag. Consider, for instance, the finish of the March 19 Xfinity race at Auto Club Speedway, where Kyle Busch appeared to have a lock on his fourth consecutive series win until a blown tire handed the lead to Daniel Suarez. They were on the final lap, so it looked like Suarez would pick up his first win in the series, but his team had played it a bit too close on fuel, and the 24-year old driver from Monterrey, Mexico ran out of fuel. This handed the lead back to Busch, who was trying to limp his badly crippled car to the finish, but it was the fast-closing Austin Dillon who passed Busch on the final turn to win the event.
The moral of the story? It’s never over until the checkered flag flies, and sometimes that’s a problem for teams that have either miscalculated their fuel requirements, botched a fuel stop, or became the victim of extra laps caused by late-race cautions. Fuel-mileage races are the subject of complaints from die-hard race fans who want to see the pure performance of the drivers and their cars determine the outcome. For others, though, it adds an interesting element of strategy to the competition, often requiring crew chiefs to make pit-stop timing decisions based on fuel efficiency and the probability of late-race cautions and overtime laps. Fuel shortages have been seen to completely change the outcome of an event, much to the chagrin of some, or to the delight of others.
In order to manage the complexities of calculating fuel requirements, teams will typically use portions of their allotted on-track test time to compute miles-per-gallon (mpg) averages under race conditions. Of course, it’s not a precise measurement, since actual race conditions differ substantially from test sessions, with the amount of passing, drafting, and (occasionally) evasive maneuvering necessary during the race, coupled with race day weather conditions (temperature, humidity, etc.) also affecting the mix. But it’s a measurement they can at least use as a base to calculate their needs.
So, what kind of fuel mileage do the cars actually experience during a race? Naturally, it varies depending on the track, but many experts put the mpg figure in the 4- to 5-gallon range running at speed, and 6- to 7-mpg under caution. In 2012, NASCAR changed the landscape dramatically by introducing electronic fuel injection to replace carburetors in the cars’ fuel delivery system, throwing the race teams yet another curve as they calculated their fuel loads. As the sport has evolved, so too has the composition of the tires and the aerodynamics of the car bodies, so much so that there is a lot the teams and the driver can do to stretch fuel between pit stops. For example, when a fuel-mileage situation appears to be developing in the late stages of a race, many drivers will revert to a conservation strategy, doing things like coasting into a turn rather than using the throttle as a brake, drafting with other cars to reduce drag, or changing their angle of entry into a turn. If a caution period is in effect, you’ll often see drivers turn off their ignition (being careful to maintain the required speed) and restart after the speed drops (electronic fuel injection has enabled drivers to perfect this strategy, since it takes less fuel to restart than carburetors). No matter what they do, it adds tremendously to the unpredictability of the finish, again to fans’ chagrin or delight.
One final piece of information on fuel…NASCAR mandates the use of Sunoco Green E15 – a 98 octane fuel blend specifically engineered for high-performance engines. If you’re wondering why it’s called “Green E15” it’s because the fuel is actually green in color. Pit crews use filler cans (called “dump cans”) weighing about 94 lbs. to fuel the cars during a pit stop, usually dumping two full cans during a single stop. All of the cans are filled and re-filled by Sunoco personnel at a master station inside the track, and then carted back to the pit area by the team.