At our last race we had two different fuel jugs, VP and Hunsaker. Both jugs hold about 5.5 gallons. The Hunsakers have unleaded fuel nozzles and pour a lot slower, but they have a convenient venting system that keeps you from getting gasoline on your race shoes.
I was curious how fast each can could dump its contents, so I filled them up with about 5 gallons of water and did a little test. But first, let’s see the contenders and how I modified them.
Hunsaker
My Hunsaker jugs have the small diameter nozzles that fit a standard unleaded restrictor plate. This has been useful for the Lemons team I race with, since their car (minivan), is street legal. The small nozzle’s .59” inside diameter (ID) restricts the amount of fuel that can flow, and makes fueling take a lot longer.
But my race car doesn’t have the unleaded restrictor plate, and so it’s kind of silly to use the Hunsaker cans as is. However, if I remove the nozzles, the large diameter tubing on the Hunsaker is too large to fit in my filler tank neck. So I made new nozzles that were as large as I could fit inside the clear tubing. I bought 1.25” aluminum tubing which has a 1.12” ID.
VP Jugs
We typically use the VP jugs for fueling because the hose is a larger diameter and they dump faster. The VP caps have a screw-in plug, and if you remove it, you can thread in a brass adapter that fits a 1” tube. Add a piece of tubing and a hose clamp and you’re done. The inside diameter of the brass adapter is 3/4”.
At the last Lemons race, my teammate Dieter modified one of my VP jugs with a Hunskaker-like air vent. This seemed to work pretty well, as no fuel escaped the vent or got on our shoes. I bored out the vent tube a bit to give it freer breathing, it looks like this:
Speed test
First up is the standard Hunsaker with unleaded nozzle: 44.4 seconds. That’s with the small air valve popped open. My teammate Pat always removes the entire vent cap from the Hunsaker jugs, instead of just opening the vent. I always thought that was silly, but I wanted to see what the difference was in dump time: 38 seconds. Huh, he wasn’t wrong about that.
Next up is the standard VP jug with homemade nozzle: 25.4 seconds. Having seen the benefit of a larger vent hole, I opened up the vent on the VP can. This can also has the “poor-man’s” Hunsaker vent, which is basically a long piece of tubing on the vent hole so you can invert the can and no gas drips out. This one dumps at 22.5 seconds, better still!
Finally, I tested the Hunsaker fuel jug with an aluminum 1-1/4” tube in place of the unleaded nozzle. Having already seen the benefit of the unscrewing the vent cap, I did that: 10 seconds. Woot!
| Fuel Can Configuration | ID | Seconds |
| Hunsaker, unleaded nozzle, small vent | .59″ | 44.4 |
| Hunsaker, unleaded nozzle, unscrew cap | .59″ | 38.0 |
| VP with standard air vent | .75″ | 25.4 |
| VP with larger vent and tubing | .75″ | 22.5 |
| Hunsaker with 1-1/4″ aluminum nozzle | 1.12″ | 10 |
I was actually unprepared for how fast the last configuration dumped the fuel, and could be off by a second when I fumbled to time it. It doesn’t really matter anyway, the point is to use the largest diameter nozzle you can, and don’t neglect the size of the air vent.
Occam's Racer 
This is great. Less time means less strain holding a 35 lb jug of fuel in the air. But, for those who are not endurance racing, that is, not on the clock while fueling, you might NOT want to drill out the air vent. Faster flow means less time to react when the tank reaches full, and more fuel on the ground if your reaction is too slow.
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This may be a stupid question but it just occurred to me – for endurance racing, where you’re trying to get as much fuel into the vehicle as possible, when you’re using a jug how to do you deal with the tank being full? Do you just dump gas in until it stops pouring then pull the hose out and dribble a little? That doesn’t seem like the right answer, especially with a top fill like a Miata, but I can’t come up with anything else that doesn’t depend on you only wanting to put a known fixed amount of gas in.
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There are a few ways to do this. I have a clear fuel line inside the car and a see-through panel in the bodywork, so I can see the fuel going in. Most people simply dump fuel until it starts to gurgle, and then pull the nozzle out quickly when they see it coming up. Or they simply let it overflow, and stop when that happens. This is not as terrible as it seems, as long as you route the fuel overflow tube out the back past the bumper to the spill tray. The overflow tube on a Miata dumps fuel onto the (hot) left rear brake, so you have to re-route this for safety anyway.
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