Typically, cars are most efficient at 45-50mph. As well as fuel economy differing from vehicle to vehicle, it is also dependent on a number of other factors such as tyre pressure, presence of roof racks, and driving style – all of which are covered in this guide.
Midsize conventional gasoline cars achieve their best fuel economy at 55 mph. The fuel economy of midsize conventional diesel cars declines gradually from 45 to 55 mph and then drops quickly thereafter. The midsize hybrid electric vehicle loses efficiency more evenly between 45 and 75 mph.
Most cars, vans, pickup trucks and SUVs are most fuel-efficient when they're travelling between 50 and 80 km per hour. Above this speed zone, vehicles use increasingly more fuel the faster they go. For example, at 120 km per hour, a vehicle uses about 20% more fuel than at 100 km per hour.
But, in general, the most efficient speed to drive is between 40 mph and 55 mph. It's important to understand that engines consume fuel, even when idle. So, if your car's at 1 mph, it's actually quite inefficient since your car isn't covering any significant distance while it's still consuming gas.
Cars use 50% of their energy overcoming aerodynamic drag. Reducing highway speed to 55 mph or less can improve fuel economy between six to eight miles per gallon.
The quicker you drive, the more fuel you consumption it is as simple as that. Department for Transport figures state that you will use up to 9% more fuel driving at 70mph than you would at 60mph, and up to 15% more fuel than driving at 50mph.
Air conditioning uses fuel
An air-conditioning (a/c) system can increase fuel consumption by up to 20% because of the extra load on the engine. The actual load depends on the vehicle's interior size, the outdoor temperature and other conditions.
The short answer: Nope. The reason: The common understanding is that going faster burns more fuel and therefore, the slower you drive, the less fuel your car will use, but this actually isn't true. Most cars' peak fuel efficiency occurs somewhere between 50-60 miles per hour.
Cruise control can help you become more fuel-efficient and can help you save an average of 7-14% on gas thanks to its ability to maintain a continuous speed. In comparison, the constant change in acceleration and deceleration of the driver placing their foot over the pedals can eat more gas.
Anything that is listed as less than 6-litres/100km or more than 16.5km/1-litre is considered to be pretty good. The first (and most common) reference is litres per 100km (litres/100km).
A full tank of fuel weighs more, driving round with additional weight in a car or van will reduce fuel economy. However, the fuel in the tank only weighs a very small percentage of the overall car or van weight, an average of around 5%.
Does AC affect gas mileage? As a general answer, a Consumer Reports study found that, yes, running the AC does reduce gas mileage. Here are some tips to help you balance your fuel consumption with comfort.
Speeding up
To accelerate a certain vehicle to a certain speed takes roughly the same amount of fuel, however quickly you do it. The main difference is that if you accelerate quickly you will be at the faster (and less economical) speed range for slightly longer, so you'll burn fractionally more fuel.
Fuel efficient driving or ecodriving is about adopting driving techniques that maximise modern engines' efficiency. Using less fuel when driving also means that carbon emissions and air pollutants from vehicles are reduced. Ecodriving contributes to safety due to the strong focus on greater anticipation.
Braking and accelerating sharply can waste fuel, so consider (as should be done anyway) a sensible, cautious approach to driving which avoids the need for sharp braking. A more consistent approach to your speed will also help to lessen fuel consumption.
A car consumes more fuel in lower gears when accelerating. If the engine's not pulling, shift down instead of pressing the throttle. Shifting up at 2,000 rpm (1,500 rpm for diesel) gives the best mix of speed and economy.
Car heating is free
Though many people don't know it, turning on the heat does not increase the car's consumption of petrol.
Idling uses up to ½ gallon of fuel per hour (although it varies depending on the type and size of the engine). It may not seem like much, but idling for a few minutes everyday can cost you several dollars per week. MYTH: Engines need to warm up by idling, especially in cold weather.
Overall, both studies showed that driving with the windows down has a significant negative effect on the fuel efficiency — more than using the vehicle's air conditioner [source: Hill].
Otherwise known as Ultra-Premium by some brands, 98 is the highest-octane fuel currently available in Australia. Unleaded 98 provides higher engine power and overall performance in comparison to 91 and 95.
Diesel fuel is known for its high energy density and fuel efficiency, making it a popular choice for long-distance driving and heavy-duty applications. Diesel engines are often more fuel-efficient than petrol engines, providing better fuel economy and lower emissions.
If you're wondering why your car is using fuel so quickly there are several causes to consider. Low tyre pressure, dirty air filters, overloading, and poor driving habits are just a few of the many reasons why your car's fuel economy can suffer.