Gasoline, you need it. For a racecar driver, gasoline is a necessity to go places, unless you are campaigning a Tesla Plaid. This magic liquid can do wonderful things. Each gallon of gasoline has incredible amounts of potential energy, which is why as a motorsports and transportation community, we have been burning the stuff for more than 100 years.
But gasoline isn’t all checkered flags and championships. It does come with some drawbacks. Besides the obvious disadvantages, like pollution, weight is one of the issues that has to be dealt with when it comes to gasoline.
Each gallon of gasoline weighs approximately 6 pounds. I use the word approximately because, believe it or not, a gallon of gasoline from Chevron is a different weight than a gallon of gasoline from Sunoco. If you want to go down the rabbit hole of “the lightest fuel with the best octane,” be my guest — it is a deep hole. But for what we want to accomplish today, using the 6-pounds-per-gallon approximation works because regardless of what brand of fuel you are using we are going to weigh it ourselves anyway.
The basis for weighing fuel versus just using the number of gallons used in a racecar during a session comes down to two principles: 1) accuracy; 2) weight matters in impound. At the end of a race, your car has to meet a minimum weight. Nobody cares about how many gallons of fuel you used during a race. But everybody cares if your car is light after a qualifying session. If you come in light, you are disqualified.
Racecars don’t usually change much in weight during a session (tire rubber wear, driver sweat, etc.) but what does change is the amount of fuel burned while on track. If you burn 5 gallons of fuel during a session, that amounts to around 30 pounds of weight you will not have with you when you hit the scales in impound. Understanding your burn rate is important.
Using the idea that every gallon is 6 pounds and watching how many gallons of fuel you put into your car between race sessions can get you close, but it won’t be very accurate. The reason for this is the six pounds per gallon is an approximation, and measuring how much fuel you put into your car in the paddock is also an approximation. Most of us aren’t using a pump that measures to the hundredth of a gallon when we are at the track. We are filling from portable 5-gallon jugs with hard-to-read hash marks on the sides of the cans to delineate gallons. It is tough to know if you filled 4 or 4.4 gallons looking at a fuel jug.
I have measured the capacity on numerous jugs and found them to all be inaccurate with regard to how many gallons actually go into a 5-gallon can. You can assume I did this in the name of science or because I was trying to find a can that indicated “5 gallons” on the side when it really held 5.75 gallons because I was racing in the Western Endurance Racing Championship series — wink, wink — where there are specific rules for fuel jugs. Regardless of why I know this, it is knowledge that I am using to explain why weighing fuel is a more efficient way to quantify use.
Knowing exactly how much weight in fuel you are burning during a 20-minute session on track can help you more accurately know how much fuel you need to have on board to get through a 45-minute race at the NASA Championships or how little fuel you must carry for a 10-minute qualifying session where you trim the car down to go as fast as possible for one single lap. This information can only be available to you by collecting data.
At Double Nickel Nine Motorsports, we fill our racecar tanks full at the beginning of a race weekend. After the first session, we weigh the car. Then we take a full 5-gallon fuel jug and weigh it on a separate scale we have in our paddock — either on one of our corner-weighting scales or a bathroom digital scale. We write down that weight and then we fill the racecar tank until it is full. Then we weigh the fuel jug again and write that number down. Whatever the difference between the two fuel jug weights is the amount of fuel burned during the session. We keep notes of how long the car was on track during the session and approximately how many gallons we filled. What really matters is the weight not the gallons.
Because fuel level is the easiest thing to adjust on a racecar to change the weight, we use the information we glean regarding how much fuel we are burning during a session to make key adjustments during a race weekend — less for qualifying, more for the long race. This has paid dividends when it comes to hitting the scales at or near the minimum weight. For sprint racing, weighing fuel is a no brainer. However, we found that weighing gas also provided crucial data and therefore a winning strategy in endurance racing. Oh, and I forgot to mention, this is what professional race teams do. They weigh all their fuel.
When we first started endurance racing with multiple drivers, we simply looked at time on track versus a tank of gas. If the car could go an hour and a half before it needed to come in for fuel, that worked for us in a three-hour enduro. But when we started doing longer races, six hours, 12 hours, 25 hours, and we had four to five drivers getting behind the wheel, we started to fall short on data. It wasn’t as simple as one tank of gas equals an hour and a half.
We had drivers who used a lot more fuel than others. We started running out of fuel earlier than expected, which threw a wrench into our pit strategy. Our first reaction — the wrong reaction — was to scold the drivers who were running out of gas. Only after I looked at the data more closely did I realize it wasn’t as simple as looking at a tank of gas versus an hour and a half on track.
Our fuel-burning drivers were going faster, their lap times were faster, which meant in an hour and a half they drove more miles than our fuel-efficient drivers. It wasn’t that they were burning fuel faster, they were actually going farther. We needed to recognize the potential energy in a gallon of gasoline and how far it can push a car down the track. When we did that, the math was working out. Fuel weight and laps covered mattered, not just a tank of gas equals an hour and a half. We want our driver to go faster and farther. That is how you win races.
Once we had the mental breakthrough that endurance racing fuel mileage was more complicated than just looking at a tank of gas as an hour and half on the track, because it wasn’t a guarantee, then we started to collect data specific for each driver. Full disclosure, I was the worst offender on our team. Somehow I could make fuel evaporate from the tank when I was behind the wheel.
The same way we weigh gas during a sprint racing weekend — weigh the can before and after filling the car, then do the math — we did this during dynamic pit stops in an endurance race. This provided us with good information to understand how much fuel we needed for a specific time for a specific driver. We wrote all this information down on our checklists and then I transferred this data into an Excel spreadsheet to really nerd out on the information. Knowledge is power.
It may sound strange, but nowadays I don’t think about fuel mileage in miles per gallon. I think more along the lines of pounds per minute. I could try to convince you that I’m some sort of crew chief genius, but the truth is some of this arose out of necessity. The reality is my Honda Challenge racecar was so stripped down it didn’t have an odometer or a fuel gauge. I had no idea what kind of miles per gallon it used, didn’t know the miles or the gallons. But, I did have a scale and I did have a stopwatch. Using those two things, I was able to get the information we needed to be successful at the track and get our car down to minimum weight for every session, whether it was an enduro, the Championships or a qualifying session. We always made weight … barely.
So, what did we learn today? A gallon of gas is around 6 pounds. Weight matters at the end of a race. Using a scale to measure fuel usage will help you better dial in your car’s weight at the end of the race and improve your overall race strategy. And, Rob as a driver, is a total gas hog. That should do!
Rob Krider is a four-time NASA Honda Challenge 4 National Champion and the author of the novel, “Cadet Blues.”