Fuel efficiency can be measured in terms of either fuel consumption or fuel economy.
This is the amount of fuel used per unit distance; for example, litres per 100 kilometers (L/100 km). The lower the value the more economical the vehicle.
Is the distance travelled per unit volume of fuel used; kilometers per litre (km/L). In this case, the higher the number of kilometers, the more economical the vehicle.
How to increase fuel efficiency
Repairing a vehicle that is noticeably out of tune or has failed an emission test can improve fuel consumption. Repairing a faulty oxygen sensor can also improve fuel consumption.
You can improve fuel efficiently by keeping your tyres inflated to the proper pressure. Properly inflated tyres are safer and will also ensure a longer life span.
Dirty or substandard engine oil (See the section on Engine Oil)
Changing oil according to the vehicle manufacturer’s service schedule can improve fuel consumption and by using the correct grade of oil.
Fast driving, rapid acceleration and braking, wastes unnecessary energy and fuel. Sensible operation and smoother driving will ultimately lower wasted energy and fuel consumption.
Observe the speed limit
Each vehicle reaches its optimal fuel economy level at a different speed, fuel efficiency can improve significantly at speeds over 80 kph with little acceleration such at moderate speeds on the motorway. Keeping to the speed limit will help save fuel.
Remove excess weight
Avoid keeping unnecessary, heavy items in your vehicle. A load in your vehicle can reduce your fuel consumption. The reduction is based on the percentage of extra weight relative to the vehicle’s weight, and affects smaller vehicles more than larger ones. Why carry a boot full of unnecessary items when the energy wasted in moving them around with you is not necessary.
Avoid excessive idling
Generally, the larger your engine the more fuel you can waste while idling for extended periods. Avoid heavy traffic where possible choose routes with less stop/starts. Avoiding traffic may be impossible; why not invest in a GPS device that could offer alternative routes or even warn you of traffic congestion ahead.
Use cruise control
Using cruise control on the highway helps maintain a constant speed and, in most cases, will save fuel.