Fuel efficiency
- This article talks about fuel efficiency, which is closely related to fuel economy, to learn about the difference, click here.
This article refers to the thermal efficiency of internal combustion car engines. This is how well a vehicle's engine is able to convert gasoline to distance traveled, as expressed in liters per hundred kilometers, miles per gallon, or kilometers per liter.
Factors in fuel efficiency
Fuel efficiency is affected by a variety of factors. This includes the thermal efficiency of the engine, as well as mechanical losses from the drive train, tire pressure, brake efficiency, and coefficient of drag of the car. According to the US Department of energy, 5-15% of light-duty fuel consumption is a result of tires, and an improvement of up to 3% in fuel consumption is possible by properly inflating tires (this improves rolling resistance)[1].
How to improve fuel efficiency
It may not seem like it, but acceleration and speed during driving have a tremendous effect on fuel efficiency. Things like slowing down a little, not accelerating so rapidly substantially improve fuel efficiency. Also properly inflating tires to their proper pressure makes a big difference.
Car manufacturers can also improve fuel efficiency by implementing a variety of kinetic energy recovery systems, like regenerative braking, and capacitors to store electricity for rapid acceleration.
Savings based on fuel efficiency
This is a table of fuel and carbon dioxide savings based on the fuel efficiency of the vehicle. Keep in mind that the make of the vehicle is not important here. Gasoline consumed is gasoline consumed, no matter what kind of car or truck you have.
| MPG (US) | Example | km/L | L/year | kg CO2 produced | Savings from 24mpg ($1.20/L) | 5 year savings | 10 year savings |
|---|---|---|---|---|---|---|---|
| 18 | Jeep Wrangler | 7.58 | 2234 | 5,343 | Costs an extra $668.40 | -$3342 | -$6,684 |
| 24 | Toyota Camry V6 | 10.1 | 1677 | 4,011 | 0 | 0 | 0 |
| 30 | Mini Cooper Clubman | 12.63 | 1341 | 3,207 | $403 | $2,015 | $4,030 |
| 38 | Fiesta 3-cyl | 16 | 1059 | 2,533 | $741 | $3705 | $7,410 |
| 45 | VW Golf TDI | 18.95 | 894 | 2,403* | $939.60 | $4,698 | $9,396 |
| 60 | Kia Rio 1.1 CDRi | 25.26 | 671 | 1,603 | $1,208.40 | $6,042 | $12,084 |
| 73.5 | VW Golf TDI Bluemotion [2] | 30.94 | 547.6 | 1,309 | $1,355.28 | $6,776.40 | $13,552.80 |
| 114** | Nissan Leaf | 48 | --- | 844 | $1,588 | $7,944 | $15,888 |
*Diesel emits 2.7 kg CO2 per liter[3]
**MPGe
Fuel efficiency conversions
The metric system of discussing fuel efficiency is very different from the US system. In the metric systemm fuel efficiency is discussed as the number of litres that it takes to go 100 km, while in the US they concern themselves with the number of miles driven by 1 gallon of gas. The first is a measure of amount of gas divided by distance, while the second is distance divided by an amount of gas, completely opposite. The unit converter below can help explore this difference: