It is well known that car tyres with a low rolling resistance make for very fuel efficient tyres. However they’re not the only thing that can help your economical driving.
Actually, there is quite a lot you can do to save fuel where possible. This post will look at the optimal driving speed, how the weight and aerodynamics improve or hinder your fuel efficiency, as well as the various car parts that are worth paying attention to.
The optimal speed
What speed you drive at changes the amount of fuel consumed by the engine. There are various reasons for this, involving the mechanics of the engine and the ratio of power required compared to the power output used purely for driving.
While the exact number will vary depending on your specific car, the miles per gallon peak at around 55 mph. Anything above or below this will waste more fuel - generally, the further you are away from this figure, you will be wasting more fuel.
Of course, many roads have strict driving requirements, such as the various 40 mph and 30 mph limits that are found throughout the United Kingdom. However, when it comes to motorways where a national speed limit is enforced (70 mph), you can instead opt to drive at 55. It might make your trip longer, but it will help cut down your fuel efficiency.
Weight and aerodynamics
While your tyres focus on lowering the rolling resistance (a bigger factor for summer tyres, but also still a factor for winter tyres) there are a number of resistance features that can slow your car down. Previously, we looked at the forces of front-wheel steering systems, rear-wheel steering systems and 4x4 cars when they are turning, but here we will look at the air resistance and weight of the vehicle.
Normal cars aren’t designed to be aerodynamic to the extent that race cars are, but there are still some important ways to reduce drag and resistance. The more resistance there is, the more fuel is used to push the vehicle forward. Similar to rolling resistance, this uses up energy that isn’t directly converted into movement.
To defeat this, ensure that the car’s exterior is clean and smooth (a quick polish will often be enough). Likewise, removing roof racks and external additions when they are not in use will help decrease the drag factor. Many also argue that narrow tyres are beneficial but, while these do offer less air resistance, remember that these often come with less grip and traction as a result of the reduced contact area.
As for the weight, there is the same argument - the more a car weighs, the more power is required to move the vehicle. Because of this, you should keep the car as light as possible. Usually, this can be achieved through clearing out the boot of items that aren’t needed. Again, fixtures such as roof and bike racks add weight, even when they are not in use. The influence on driving speed is most visible when starting from a standstill. When accelerating, this weight pushes down onto the tyres, requiring energy to move.
For the car engine to work at peak efficiency, there needs to be an ideal balance of fuel and air. The latter is required to introduce oxygen and the air filter removes any dust or pollutants that would hinder the combustion process. Of course, the air filter becomes clogged as a result, and this influences the amount of air that gets through to the engine.
It is often recommended that drivers change their air filters around every 15,000 miles, although this exact figure depends on the nature of your car, your air filter and your own driving habits. As such, you should always consider changing the air filter when you notice reduced power during acceleration, even with a high revs per minute (RPM) rate. This occurs because the high RPM requires more oxygen, which the air filter is obstructing.
Similar to air filters, your oxygen and airflow sensors help control the engine’s efficiency. These monitor the airflow from the exhaust, in the case of oxygen sensors, and the airflow into the engine and many modern cars will use this data to adjust the fuel injection. As a result, a faulty sensor will disrupt the intake of your engine, often resulting in less fuel efficiency. This is hard for drivers to notice, but the sensors should be inspected around 100,000 miles or so, just to be sure they are working correctly.
Fuel efficient tyres
Of course, this also includes your tyres. A low rolling resistance offers low fuel consumption only if your tyres are in good condition. As the tyres wear down, the rolling resistance will likely change, alongside a multitude of other driving factors, such as driving comfort and grip. As such, it helps to change your tyres on a regular basis, to ensure a decent level of performance and rolling resistance.