Miles per gallon
From Wikipedia, the free encyclopedia
 |
This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2008) |
Miles per gallon (MPG) is a unit of measurement that measures how many miles a vehicle can travel on one gallon of fuel. It is used similarly in North America and the United Kingdom, although the U.S. gallon is about 83% of the Imperial gallon used in the UK.
Contents |
[edit] Conversion to SI units
Most countries other than the US and UK use the Metric (SI) units litre (approximately 0.220 Imperial gallons or 0.264 US liquid gallons) and km (approximately 0.621 statute miles). These can be combined to either km/L (efficiency) or L/100 km (consumption). The UK is a special case in this respect, as distances are measured in miles but fuel is sold by the litre. As a result, both MPG and L/100 km are usually quoted for any given vehicle, although the general public almost exclusively use miles-per-gallon. Note that because the imperial gallon is significantly larger than the U.S. gallon, MPG figures are 20.095% higher in the UK than in the U.S. for the same real fuel economy.
[edit] US liquid gallons
- 1 mi ≈ 1.609 km
- 1 gal (US) ≈ 3.785 L ≈ 0.833 gal (Imp)
- 1 MPG (US) ≈ 1.609 km / 3.785 L ≈ 0.425 km/L
- 1 MPG (US) ≈ 100 * 3.785 L / 1.609 km ≈ 235 L/100 km
- 1 MPG (US) ≈ 1 / 0.833 gal (Imp) ≈ 1.201 MPG (Imp)
[edit] Imperial gallons (UK)
- 1 mi ≈ 1.609 km
- 1 gal (Imp) ≈ 4.546 L ≈ 1.201 gal (US)
- 1 MPG (Imp) ≈ 1.609 km / 4.546 L ≈ 0.354 km/L
- 1 MPG (Imp) ≈ 100 * 4.546 L / 1.609 km ≈ 282 L/100 km
- 1 MPG (Imp) ≈ 1 / 1.201 gal (US) ≈ 0.833 MPG (US)
[edit] Increase in MPG and decrease in L/100 km
One should note that MPG works differently than litres per hundred kilometres. L/100 km denotes a rate of fuel consumption, while MPG is a measure of fuel economy (or 'gas mileage'). If a car uses less fuel, the MPG increases, and L/100 km decreases, but the percentages will not match, because the values are reciprocal.
For example, 20% better mileage does not mean 20%, but 16.7% less fuel. This comes from the following calculation: 20% is 1.2 times bigger distance, therefore 100% / 1.2 = 83.3% of the original fuel consumption, or 16.7% less fuel.
If a driver who travels 15,000 miles a year switches from a vehicle with 10 MPG to 12 MPG average fuel economy (0.10 gallons per mile to 0.083 gallons per mile), 250 gallons are saved. A similar 20% improvement in exchanging a 30 MPG for a 36 MPG (0.033 gallons per mile for 0.027 gallons per mile) vehicle saves only 83 gallons for similar driving patterns.
Since L/100 km is linear instead of reciprocal, a driver who travels 15,000 km a year and switches from a vehicle with 20 L/100 km to one with 19 L/100 km has the same 150 L/year savings as someone who switches from 5 L/100 km to 4 L/100 km.
Because consumption is an inverse function of MPG, MPG can be a misleading indicator of fuel efficiency gains. People intuitively take the difference in MPG when comparing two cars. This leads them to underestimate the savings from small improvements on low MPG cars (e.g., 14 to 20 MPG, which saves twice as much fuel over a given distance as the improvement from 33 to 50 MPG, www.mpgillusion.com). A measure of "Gallons Per Mile" (GPM), such as gallons per 100 miles, provides an accurate view of consumption for a given distance of driving. Unlike MPG, the GPM of one car can be subtracted from the GPM of another car to get a direct measure of fuel savings.
[edit] Conversion Formulas
In the following conversion formulas, MPGUS refers to miles per U.S. gallon, MPGIMP refers to miles per Imperial gallon, KMPL refers to kilometres per litre (km/L) and LPHKM refers to litres per 100 kilometres (L/100 km). To simplify the the formulas, they do not specify the units.
[edit] To MPG (US)
MPGUS ≈ (3.785 / 1.609) * KMPL ≈ 2.352 * KMPL
MPGUS ≈ 100 * (3.785 / 1.609) / LPHKM ≈ 235 / LPHKM
MPGUS ≈ 1.201 * MPGIMP
[edit] To MPG (Imp)
MPGIMP ≈ (4.546 / 1.609) * KMPL ≈ 2.825 * KMPL
MPGIMP ≈ 100 * (4.546 / 1.609) / LPHKM ≈ 282 / LPHKM
MPGIMP ≈ 0.833 * MPGUS
[edit] To km/L
KMPL ≈ (1.609 / 3.785) * MPGUS ≈ 0.425 * MPGUS
KMPL ≈ (1.609 / 4.546) * MPGIMP ≈ 0.354 * MPGIMP
KMPL = 100 / LPHKM
[edit] To L/100 km
LPHKM ≈ 100 * (3.785 / 1.609) / MPGUS ≈ 235 / MPGUS
LPHKM ≈ 100 * (4.546 / 1.609) / MPGIMP ≈ 282 / MPGIMP
LPHKM = 100 / KMPL
[edit] Conversion Tables
The conversion tables give a quick overview of the relationship between the different measurement units, MPG (U.S.), MPG (Imperial), km/L, and L/100 km.
[edit] Conversion from MPG
| MPG (Imp) | MPG (US) | km/L | L/100 km |
|---|---|---|---|
| 5 | 4.2 | 1.8 | 56.5 |
| 10 | 8.3 | 3.5 | 28.2 |
| 15 | 12.5 | 5.3 | 18.8 |
| 20 | 16.7 | 7.1 | 14.1 |
| 25 | 20.8 | 8.9 | 11.3 |
| 30 | 25.0 | 10.6 | 9.4 |
| 35 | 29.1 | 12.4 | 8.1 |
| 40 | 33.3 | 14.2 | 7.1 |
| 45 | 37.5 | 15.9 | 6.3 |
| 50 | 41.6 | 17.7 | 5.6 |
| 55 | 45.8 | 19.5 | 5.1 |
| 60 | 50.0 | 21.2 | 4.7 |
| 65 | 54.1 | 23.0 | 4.3 |
| 70 | 58.3 | 24.8 | 4.0 |
| 75 | 62.5 | 26.6 | 3.8 |
| 80 | 66.6 | 28.3 | 3.5 |
| 85 | 70.8 | 30.1 | 3.3 |
| 90 | 74.9 | 31.9 | 3.1 |
| 95 | 79.1 | 33.6 | 3.0 |
| 100 | 83.3 | 35.4 | 2.8 |
| MPG (US) | MPG (Imp) | km/L | L/100 km |
|---|---|---|---|
| 5 | 6.0 | 2.1 | 47.0 |
| 10 | 12.0 | 4.3 | 23.5 |
| 15 | 18.0 | 6.4 | 15.7 |
| 20 | 24.0 | 8.5 | 11.8 |
| 25 | 30.0 | 10.6 | 9.4 |
| 30 | 36.0 | 12.8 | 7.8 |
| 35 | 42.0 | 14.9 | 6.7 |
| 40 | 48.0 | 17.0 | 5.9 |
| 45 | 54.0 | 19.1 | 5.2 |
| 50 | 60.0 | 21.3 | 4.7 |
| 55 | 66.1 | 23.4 | 4.3 |
| 60 | 72.1 | 25.5 | 3.9 |
| 65 | 78.1 | 27.6 | 3.6 |
| 70 | 84.1 | 29.8 | 3.4 |
| 75 | 90.1 | 31.9 | 3.1 |
| 80 | 96.1 | 34.0 | 2.9 |
| 85 | 102.1 | 36.1 | 2.8 |
| 90 | 108.1 | 38.3 | 2.6 |
| 95 | 114.1 | 40.4 | 2.5 |
| 100 | 120.1 | 42.5 | 2.4 |
[edit] Conversion from km/L and L/100 km
| L/100 km | km/L | MPG (US) | MPG (Imp) |
|---|---|---|---|
| 1 | 100.0 | 235.2 | 282.5 |
| 2 | 50.0 | 117.6 | 141.2 |
| 3 | 33.3 | 78.4 | 94.2 |
| 4 | 25.0 | 58.8 | 70.6 |
| 5 | 20.0 | 47.0 | 56.5 |
| 6 | 16.7 | 39.2 | 47.1 |
| 7 | 14.3 | 33.6 | 40.4 |
| 8 | 12.5 | 29.4 | 35.3 |
| 9 | 11.1 | 26.1 | 31.4 |
| 10 | 10.0 | 23.5 | 28.2 |
| 15 | 6.7 | 15.7 | 18.8 |
| 20 | 5.0 | 11.8 | 14.1 |
| 25 | 4.0 | 9.4 | 11.3 |
| 30 | 3.3 | 7.8 | 9.4 |
| 35 | 2.9 | 6.7 | 8.1 |
| 40 | 2.5 | 5.9 | 7.1 |
| 45 | 2.2 | 5.2 | 6.3 |
| 50 | 2.0 | 4.7 | 5.6 |
| 55 | 1.8 | 4.3 | 5.1 |
| 60 | 1.7 | 3.9 | 4.7 |
| km/L | L/100 km | MPG (US) | MPG (Imp) |
|---|---|---|---|
| 5 | 20.0 | 11.8 | 14.1 |
| 10 | 10.0 | 23.5 | 28.2 |
| 15 | 6.7 | 35.3 | 42.4 |
| 20 | 5.0 | 47.0 | 56.5 |
| 25 | 4.0 | 58.8 | 70.6 |
| 30 | 3.3 | 70.6 | 84.7 |
| 35 | 2.9 | 82.3 | 98.9 |
| 40 | 2.5 | 94.1 | 113.0 |
| 45 | 2.2 | 105.8 | 127.1 |
| 50 | 2.0 | 117.6 | 141.2 |
| 55 | 1.8 | 129.4 | 155.4 |
| 60 | 1.7 | 141.1 | 169.5 |
| 65 | 1.5 | 152.9 | 183.6 |
| 70 | 1.4 | 164.7 | 197.7 |
| 75 | 1.3 | 176.4 | 211.9 |
| 80 | 1.3 | 188.2 | 226.0 |
| 85 | 1.2 | 199.9 | 240.1 |
| 90 | 1.1 | 211.7 | 254.2 |
| 95 | 1.1 | 223.5 | 268.4 |
| 100 | 1.0 | 235.2 | 282.5 |
