To begin with, it makes no sense to rely on the fuel economy figures given in the vehicle specifications and car manuals. It happens that the data given in such documents are only close to the values of real consumption.However, for the most part to the "documented" parameter should be added a liter, a few liters, or even double the liters, if you are driving a large and heavy four-wheel drive car, in adverse conditions
Why are there such discrepancies? The fact is that any of the methodologies of consumption calculation is carried out in greenhouse conditions, namely - on the stands, where the car only simulates acceleration, braking and acceleration, typical for driving out of town, in the city and in the mixed mode.
For example, according to the standards of the European evaluation methodology, the consumption results for urban conditions are taken when the car accelerates to 50 km/h in an endless 26 seconds. In this case, including stops before traffic lights and invariably unhurried speeding are simulated. When estimating parameters of driving in the mixed cycle, driving up to 70 km/h is taken as a starting point. In this case the car switches off all electric power consumers and uses tires with minimum allowable tread in order to reduce energy losses for friction.
It is clear that in real conditions it is problematic to follow this way of driving - you will interfere with other traffic participants, and it is hardly possible to maintain a steady driving tempo contributing to economy. The same concerns driving without the switched on headlights and air conditioner - it will hardly be possible to drive so at night and in hot weather.
Nevertheless, if you have a task to economize fuel as much as possible, the speed mode of 75 km/h will be optimum. To keep such speed in a city in absence of traffic jams, by the way, is quite realistic, if speed limits allow. As regards the algorithm of speed gain, for maximum economy it is necessary to start as the test bench does - to accelerate up to 50 km/h for those same 26 seconds and thus to watch that the tachometer needle does not get higher than 1500 rpm.
On the highway for maximum economy will have to be built in the rightmost lane and maintain cruising 75 - 80 km / h. Ideally, if you can get behind the same slow traffic (truck, cargo van, grandfather on the old "Zhiguli", etc.). Then the fuel consumption can be reduced even more because of the reduction of frontal resistance.
One more important moment is connected with a choice of correct gear in transmission. It is desirable to activate the highest, direct gear, for which in the case of automatic transmissions, it may be necessary to activate manual mode. Shift up as much as possible without hesitating, for example, immediately after "second" include "fourth" and watch that the tachometer needle remains on low revolutions.
At the same time, if driving conditions allow, it will be not superfluous to disconnect climate system and other powerful consumers of electric power, which will also contribute to the economy of driving. Thus, working headlights require additional 0,5 l/100 km, therefore, it is better to use daytime running lights or fog lights. One more tip - to raise pressure in wheels by 0,2 bar - so, it is possible to count on reduction of fuel consumption.
In any case, remember, that "vegetable" manner of driving will for certain cause irritation at neighbors. Therefore, we repeat, keep in the slow right lane.