At high speeds, the car starts to consume more fuel, and the trip becomes not only less safe, but also more jittery. what is the most fuel efficient speed for this we compared consumption in three identical cars and assessed which economical speed on the highway is best associated with fast travel time and moderate fuel consumption.

The legal speed limit on highways is 90 to 120 km/h in most of the world like the US, Europe, and Canada, but the reality is that drivers often either drive much slower or “rush” forward at much higher speeds. The limit is most often exceeded by users of expensive premium cars and business cars, while motorway traffic makes it difficult to overtake trucks and drivers in older cars, for whom reaching a speed of 120 km / h is a problem.

## How much does it cost to drive on the highway?

The overtaking maneuver of a large truck creates a long “rope” of cars in the left lane very quickly, especially on a highway with two lanes in one direction. This not only annoys drivers but also creates danger, so the minimum safe speed on the freeway must be at least 90 km/h.

The maximum is already determined by weather conditions, the current traffic situation, and regulations, although not everywhere, for example in Germany there is no legal speed limit at which you can drive on the motorway.

## what is the most fuel efficient speed? Experimental values

We conducted a test to answer the question of what is the most fuel-efficient speed. For its implementation, three identical vehicles were used ( Hyundai Tucson with a power of 141 hp with 1.7 CRDi), which had to overcome 1000 km at different speeds (100, 120, and 140 km/h).

The test was to show how a typical car consumes fuel depending on the increase in driving dynamics. In each of them, the actual average speed was measured.

### Speed 100 km/h: best speed for fuel economy km/h

Moving at a speed of 100 km/h, it was possible to achieve a consumption of 6.6 l / 100 km. for Hyundai Tucson. On motorways, slower passenger cars and minibusses tend to maintain this speed, and practice shows that it is not necessary to overtake them. This allows very smooth maneuvering and minimizes the amount of braking and thus maintains the set speed for as long as possible. As a result, the actual average speed was only 4 km/h slower than expected.

Contrary to appearances, at a speed of about 100 km / h, many cars are moving along the highway, not just vans. This is the upper limit of relatively economical driving, which does not require frequent braking and overtaking.

### Speed 120 km/h

By increasing the speed to an acceptable one, you can notice a significant increase in fuel consumption most cars do not consume much up to 100 km / h. When driving at 120 km/h, you should be prepared for frequent overtaking, but this is not something to worry about too much. The car covered 500 km in just over 4 hours, which is 60 minutes shorter than a driver traveling 100 km/h.

120 km/h is the optimal highway speed. This does not pose a threat and does not yet cause very high fuel consumption for the car.

### Speed 140 km/h

Fuel consumption increases and range decreases – at 140 km/h, the Hyundai Tucson burned over 3 liters of fuel for every 100 km. This resulted in a difference in gas bill compared to a car traveling at 100 km/h, but the driver reached the destination 1.5 hours faster. However, such fast driving requires frequent (sometimes sudden) braking and visits to gas stations for refueling.

Exceeding the speed limit on the motorway disrupts the smoothness of driving and negatively affects safety (you often have to brake, and not only when there are trucks in front of you).

## Differences in combustion in other vehicles

The Hyundai Tucson example showed that the car retains its efficiency up to about 100 km/h. Editorial measurements included 6 other vehicles that were tested under the same conditions. In general, the difference in fuel consumption between 120 and 160 km / h was from 2 to 4 liters, and in the Toyota Land Cruiser V8 up to 10 liters for every 100 km. This is due to the low aerodynamic body shape because one of the smallest differences in fuel consumption performance was recorded in the Porsche Panamera.

## Find out what is the most fuel efficient speed to drive at For Any car?

As a rule, such an optimal speed is indicated in the characteristics of any car. There is always a line with fuel consumption in different modes, including driving on the highway. The speed indicated in this line will be the most economical.

You can also focus on the average figures indicated at the very beginning of the article. That is, assume that the most economical speed is somewhere between 80 km/h and 110 km/h. You can even use the average of these two speeds, and in a rush to save money, stick to a speed of 90 km/h. This figure is suitable for most passenger cars.

The third way to find out the most economical speed is to use regular or freelance fuel software. Now, these can be installed on absolutely any car without any problems. To find out that very treasured speed, you will have to experiment. Under the same other conditions from the list above, it will be necessary to travel at different speeds, observing the readings of the BC. At the same time, you should always wait for the moment when the vehicle speed is stable (no acceleration or braking), otherwise, the readings will be distorted.

If there is no instruction manual, no onboard computer, and no confidence in the average 90 km / h, then the instantaneous fuel consumption can be roughly equated to the average. But for this, you will have to record the mileage at each refueling, and also adhere to the same cruising speed at certain periods of time. This is a long time, not entirely accurate – but quite real.

## Conclusion

Maintaining a speed of **100 km/h on the motorway means the most fuel efficient speed **and safe, stress-free driving. However, taking into account the travel time of the route, the most advantageous option is to drive at a speed limit of 120 km/h. Driving at 140-160 km/h is probably the fastest route but by far the least economical and quite dangerous.

Moreover, over longer distances, the time spent on additional refueling results in the fact that we lose almost all the time, while at the same time when the car is going slower, it does not need to stop and top up the fuel level. That’s why you shouldn’t experiment with speed on highways.

**The quieter you go, the further you’ll get!**