Some vehicles, especially older models and vehicles built for long-distance travel, have built-in reserve tanks in addition to the primary fuel tank.
These reserve tanks hold about 15% of the maximum amount of fuel that can be contained in the primary fuel tank. When the fuel in the primary tank runs dangerously low and cannot be immediately replenished, the driver switches to the reserve tank, allowing the vehicle to cover some extra miles.
However, modern cars do not have reserve tanks. Instead, their fuel tanks adopt the concept of these auxiliary tanks. In the design of modern vehicles, the fuel indicator notifies the driver prematurely of the need to top up the fuel.
When the low fuel warning is displayed, the vehicle’s fuel tank is not empty but has about 10% to 15% of fuel. This is known as the reserve fuel, which allows you to get to the nearest gas station before your vehicle stalls.
Differences Between Reserve Tank and Reserve Fuel
A reserve tank is a secondary fuel tank built separately from the primary, secondary tank. The reserve tank is usually connected to the primary tank via a valve.
The driver flips a switch or pushes a button to switch to the reserve tank when the fuel in the primary tank runs low. This allows the reserve tank to supply fuel directly to the engine, thus enhancing the convenience of traveling.
In some cases, the reserve tank is synonymous with the reserve fuel tank.
Reserve fuel refers to the fuel contained in the reserve tanks of some vehicles and the extra fuel available for use when the low fuel indicator is displayed in cars with only one fuel tank.
In vehicles without reserve tanks, the reserve fuel is contained in the bottom of the tank, below the low fuel indicator level. The reserve fuel is advantageous to drivers as it enables them to safely access a fueling station before the vehicle runs out of fuel, thus damaging the engine or disrupting their travel.
However, experts recommend refilling your fuel tank as soon as the low fuel indicator is displayed and using the reserve fuel in emergencies only.
How Do You Know If Your Car Has a Reserve Tank?
This fact will be indicated in the car’s manual if your car has a secondary reserve tank. Moreover, on your vehicle’s dashboard, you will have a switch or button that allows you to switch from the primary tank to the reserve tank, informing you of the presence of the reserve tank.
Most modern cars have reserve fuel. This information will be displayed under the gas tank specifications to determine the quantity of reserve fuel for your vehicle.
The reserve fuel is approximately the same as in a secondary fuel tank, 15% of the fuel tank capacity for most vehicles. You can calculate the exact amount of reserve fuel depending on your vehicle’s specifications.
How Far Past Empty Can You Drive?
The distance you can cover when running on fuel reserve depends on the car model and the quantity of reserve fuel. To determine how far you can drive once the fuel indicator turns on, you need to calculate your vehicle’s volume of reserve fuel.
Next, calculate your vehicle’s fuel economy, which is the fuel consumption of your vehicle. However, take note that fuel economy is influenced by driving conditions such as speed, acceleration, slope, and loads.
For example, cars tend to consume more fuel when going uphill, carrying heavy loads, and driving slowly.
Let us estimate the distance a 2017 Audi SQ5 can cover on an empty tank while traveling on generally flat terrain at an estimated 74km/hr speed.
If the fuel economy is 9 liters/ 100 km and the reserve tank holds 10 liters of fuel (15% of 70 liters), the average distance the car covers is 111km, which is quite impressive. However, most cars’ average maximum length they can cover is 80 km past empty.
Reserve tank and reserve fuel are advantageous car specifications that enhance driving convenience. Reserve tanks are standard in older vehicle models and long-distance traveling vehicles.
However, modern cars apply the reserve tank principle by having reserve fuel stored in the fuel tank. Once the fuel reaches the reserve level, the fuel indicator is displayed, warning the driver of low fuel.
Although the reserve tank can allow us to drive for quite a long distance, this action is ill-advised because of the dirt that accumulates at the bottom of the fuel tank, which can be transferred to the engine through the reserve fuel.