Fuel prices are higher than ever. Diesel cost more than two euros per liter at times. The most effective means of combating high fuel consumption is under your right foot.
Information on the display of many modern cars also shows how to save money and CO2: Disengage the clutch at the traffic lights, and the automatic start-stop system will kick in. Or: Only disengage the clutch below 900 revolutions, because as long as the engine is braking, consumption is zero. How can a cell phone help?
ADAC: 40 percent of fuel gauges are inaccurate
Most cars display the current consumption, the average consumption over 100 kilometers and perhaps the long-term consumption over several thousand kilometers. The on-board computer supplies the values to one decimal place. But are these values correct? The German Automobile Club (ADAC) investigated this. 80 car models were tested. In 40 percent of them, the on-board computer was off by more than five percent. The front-runner is an Audi Q2 35 TDI Quattro with a deviation of almost 14 percent. The good news is that most of the deviations indicate excessively high consumption. The manufacturers don't want to shine with low consumption; instead, they build in a buffer for measurement inaccuracies and one for the remaining range at the same time.
Measurement inaccuracies? It can't be that difficult to measure the level in a tank. But it is: because the fuel tanks hug the shape of the car body. Depending on the fill level, a change in level of one millimeter can add up to liters of difference either way. That's why car manufacturers don't measure tank capacity for fuel consumption, but the amount of fuel that passes through the injection nozzles. And even that is not accurate. As the ADAC has already stated.
From the test bench to the app
There is another way. Since September 2018, all new cars have had to pass the Worldwide Harmonized Light Vehicles Test Procedure, or WLTP for short. On the chassis dynamometer, manufacturers, TÜV, DEKRA and others measure pollutant emissions and use them to calculate consumption. WLTP also takes into account the best-equipped model with the widest tires. However, consumption when driving uphill is completely different from consumption on the level, and during stop-and-go the consumption values for braking and acceleration are far higher than those of the driving cycle on the chassis dynamometer. This is the approach for fuel-saving apps, which thus complement the complex measurements of tank levels and injectors.
Save fuel with your cell phone
Fuel-saving apps are even more accurate than the WLTP cycle itself. They calculate fuel consumption using current driving data as a percentage deviation from the globally recognized driving cycle. That's because almost all cell phones have chips built into them that use satellite data to calculate their position once a second. And not just in two dimensions, but in three. This means that the cell phone records both the speed and the gradient. The rest is Newtonian physics: The app calculates the current fuel consumption from the weight, efficiency of the engine, energy content of the fuel, wind and rolling resistance together with the data from the position. The position data provides values for idle times, acceleration and braking.
An app becomes the norm
To ensure that all fuel-saving apps perform the calculation in a comparable way, there is a standard: ISO 23795-1 Intelligent transport systems – Extracting trip data using nomadic and mobile devices for estimating CO2 emissions. Intelligent transport systems – Extracting trip data using nomadic and mobile devices for estimating CO2 emissions. The blueprint for the standard is an app from T-Systems. The "Low Carbon Mobility Management" algorithm has already proven in a test in China that it works, helps save fuel and has the potential to improve the air. Together with a parcel service provider, T-Systems equipped a fleet of vehicles with the app in the megacities of Dongguan and Qingdao. The result: In Dongguan, the parcel service saved almost 20 percent fuel per ton of freight. In Quingdao, the service provider saved close to 12 percent. In total, this corresponds to 341 tons of CO2.
Good for fleets
Of course, it's not enough to put the cell phone with the app on the passenger seat. The two levers for potential savings are driving behavior and the route. A fleet operator can use acceleration values to give tips to individual drivers, for example. After all, there is high fuel-saving potential under their right feet. The second lever is the planned route. Those who avoid inclines, traffic lights and congestion can do even more for their wallets and the environment. This provides fleet operators with a simple and cost-effective tool. Parcel service providers also have to record the weight of the freight. But this is included in the electronic information for each parcel and is recorded via scan during loading.
