Featured Research

from universities, journals, and other organizations

Why 'Filling-it-up' Takes More Than 'Tank Capacity'

Date:
October 26, 2005
Source:
National Institute of Standards and Technology (NIST)
Summary:
You fill up your "empty" fuel tank at the gas station and the pump charges you for more gallons than the tank's rated capacity. Are you being deliberately overcharged? A NIST 's weight and measures expert explains in a recent paper why this may happen even at reputable gas stations.

Simplified schematic of a vehicle fuel tank (not to scale).
Credit: J.Williams/NIST

You fill up your "empty" fuel tank at the gas station and the pump charges you for more gallons than the tank's rated capacity. Are you being deliberately overcharged?

Related Articles


Unauthorized tampering with pumps does happen, even though state and local weights and measures officials regularly check gasoline pumps to ensure their accuracy. But there are also legitimate reasons for a discrepancy between the amount of fuel metered by a gas pump and an automobile's rated fuel tank capacity, according to a recent paper from the National Institute of Standards and Technology (NIST).

For example, some manufacturers estimate that actual fuel tank capacity can vary as much as 3 percent from the tank capacity rating because of design characteristics, the manufacturing process, and even the physics associated with the components that monitor emissions and the electronics of the fuel system and fuel indicators.

NIST notes that it is important to consider which parts of a vehicle's fuel tank are used to determine its capacity rating and what happens to these components when operating and fueling a vehicle. A small area at the bottom of a full tank is considered unusable because the fuel pump cannot reach that level to draw fuel. In addition, the tank's rated capacity does not include the "vapor head space," the uppermost portion of the tank compartment, nor does it include the volume of the filler pipe where fuel enters the vehicle.

Drivers, however, sometimes fill the tank beyond the pump's automatic shut-off point, resulting in fuel being drawn into the vehicle's vapor recovery system or filler pipe. Similarly, if the lanes that surround the service station pumps are not level, fuel can shift into the vapor space allowing more fuel to be delivered into the tank.

NIST cautions against using the "half full" reading on the fuel gauge to determine the exact number of gallons it will take to fill the tank. The fuel gauge is intended as an approximate indication of the fuel level. Manufacturers may set the "full" indicator at a level just below the tank's actual capacity. Reserve fuel also can be present if the manufacturer designs the fuel gauge to indicate empty at a level above the actual point where the tank runs out of gas.

###

*J. Williams. Fuel Tank Capacity and Gas Pump Accuracy. August 2005. Weights and Measures Quarterly newsletter is available at http://ts.nist.gov/ts/htdocs/230/235/archive/B-014.pdf.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology (NIST). Note: Materials may be edited for content and length.


Cite This Page:

National Institute of Standards and Technology (NIST). "Why 'Filling-it-up' Takes More Than 'Tank Capacity'." ScienceDaily. ScienceDaily, 26 October 2005. <www.sciencedaily.com/releases/2005/10/051023120710.htm>.
National Institute of Standards and Technology (NIST). (2005, October 26). Why 'Filling-it-up' Takes More Than 'Tank Capacity'. ScienceDaily. Retrieved March 27, 2015 from www.sciencedaily.com/releases/2005/10/051023120710.htm
National Institute of Standards and Technology (NIST). "Why 'Filling-it-up' Takes More Than 'Tank Capacity'." ScienceDaily. www.sciencedaily.com/releases/2005/10/051023120710.htm (accessed March 27, 2015).

Share This


More From ScienceDaily



More Matter & Energy News

Friday, March 27, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Inspectors Found Faulty Work Before NYC Blast

Inspectors Found Faulty Work Before NYC Blast

AP (Mar. 27, 2015) An hour before an apparent gas explosion sent flames soaring and debris flying at a Manhattan apartment building, injuring 19 people, utility company inspectors decided the work being done there was faulty. (March 27) Video provided by AP
Powered by NewsLook.com
Facebook Building Plane-Sized Drones For Global Internet

Facebook Building Plane-Sized Drones For Global Internet

Newsy (Mar. 27, 2015) Facebook on Thursday revealed more details about its Internet-connected drone project. The drone is bigger than a 737, but lighter than a car. Video provided by Newsy
Powered by NewsLook.com
Residents Witness Building Explosion, Collapse

Residents Witness Building Explosion, Collapse

AP (Mar. 26, 2015) Witnesses recount the sites and sounds of a massive explosion and subsequent building collapse in the heart of Manhattan&apos;s trendy East Village on Thursday. (March 26) Video provided by AP
Powered by NewsLook.com
Amazon Complains U.S. Is Too Slow To Regulate Drones

Amazon Complains U.S. Is Too Slow To Regulate Drones

Newsy (Mar. 25, 2015) Days after getting approval to test certain commercial drones, Amazon says the Federal Aviation Administration is dragging its feet on the matter. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins