Whether you’re pumping diesel or gasoline, pretty much expect to get what you pay for. You do – only if the fuel coming out of that nozzle is 60 degrees. Anything warmer than that, and you’re getting cheated.
Fluids expand as they warm and contract when they cool. Diesel and gasoline are no exception. How much? Estimates vary, on average from 1 percent to 3 percent just for diesel, depending on how hot it is and whom you ask.
So if that gasoline or diesel you just pumped into your car or big rig is hotter than 60 degrees, your gallon just got “bigger.”
Is bigger really better?
Imagine this: Btu units are marbles filling a gallon glass jar surrounded by diesel or gas. When fuel is warmed, the Btu – marbles – separate from each other half an inch, and some are forced out the top of the jar. The jar has the same volume – it still measures out at a gallon – but has less Btu “marbles” to burn.
If that fuel you just pumped into your rig is 70 or 80 degrees – it’s basically weaker. It doesn’t have the same burn for the buck that it would have had at 60 degrees.
If you consider those two things – Btu content and volume – together, then you will see the problem. This is a perfect example of where the “bigger isn’t always better” adage proves true.
The magic number
Because the amount of energy per gallon varies with its temperature, engineers need a baseline for measuring and calculating. Diesel and gasoline volumes at the wholesale level are standardized to 60 degrees – the magic number – which is about the temperature of old single-walled, underground storage tanks. At 12 feet deep, the contents of those tanks are kept a relatively constant temperature throughout the year.
Today’s double-walled tanks keep fuel near the temperature it was when it was delivered. They act just like a thermos, and if the fuel doesn’t stay long in the tank, it can be so warm as to be labeled “hot.”
During the summer months especially, fuel can be delivered to a tank at a temperature that is nearly 40 degrees hotter than the benchmark used at the wholesale level. So if the fuel’s temperature is not compensated for at the truck stop pump, the gallon pumped into your tank will be less dense – with fewer Btu – therefore less powerful.
During the summer months, an informal OOIDA Foundation study of 32 fill-ups around the country found the coolest fuel at 71 degrees. The hottest fuel was 98 degrees.
Say a fuel retailer buys 10,000 gallons and pays for fuel and taxes on those 10,000 gallons. By selling warm fuel through pumps without temperature compensation, the retailer may be charging you and your fellow truckers for 10,100 gallons, collecting the retail price and taxes on 100 gallons more than he paid for.
Here does it stop?
It can stop at the pump – if you get involved.
Technology already exists in today’s digital fuel pumps to calculate the amount of fuel dispensed standardized to the same 60-degree benchmark that retailers buy the fuel at – reducing your power loss.
Retail stations have the technology, but for what seem to be obvious reasons, they are not excited about turning on the temperature-compensation function of their pumps. By buying fuel that’s compensated cool and selling warm fuel uncompensated, they are receiving quite a windfall in a business where profits are measured in pennies per gallon.
And if your fuel bill is 16,000 gallons, you could be paying as much as $160 more per year for energy you’re not getting. If the expansion is more like 2 percent or 3 percent, you can double or triple the savings you would realize if the pumps compensated for the expansion.
GIVE THEM A CALL
If you want this to stop, let your state Weight and Measure Administrator know what you think. Call the National Conference on Weights and Measures at (240) 632-9454 for your state’s contact person, or visit their Web site atncwm.net/statewmdir.pdf for a listing of state administrators.
By Jami Jones of the Land Line staff with contributions from Senior Technical Editor Paul Abelson and OOIDA Foundation’s John Siebert.