Is it necessary to fill the gas tank full if the car is rarely used?
For cars that are rarely used, it is advisable to fill the gas tank full (or at least three-quarters) before parking the car for a long time, but do not let it overflow. A full tank leaves little air space, thus reducing the chances of condensation, water, and rust forming inside the tank. However, a full tank is not a guarantee of problem-free operation, as gasoline itself can still degrade in quality if left too long.
There are many reasons why a car is rarely used, such as commuting by KRL, MRT, or online motorcycle taxis and only using the car on weekends. Some people have low mobility because their daily activities do not involve using a car, and the car is only used for vacations. Cars like this are often parked for days, even weeks, with just a little gasoline left. This habit may seem economical, but it can lead to repair costs later on. Therefore, it is also important for us to understand how to maintain a rarely used car.
This article explains what happens inside the tank, which is better between a full tank and an empty one, and practical steps to maintain the fuel system.
What Happens Inside the Tank When the Car Stays Idle for a Long Time?
When a car is rarely used, there are three processes that slowly occur inside the tank: condensation, rust, and gasoline aging.
- Condensation.
The empty space above the gasoline surface contains air that holds water vapor. When the temperature rises during the day and drops at night, the water vapor condenses into droplets on the tank walls and then falls into the gasoline. Astra Daihatsu Motor technician, Anjar Rosjadi, explains that the less gasoline there is, the larger the empty space and the greater the potential for water from this process. - Rust.
Water that settles at the bottom of the tank can trigger corrosion. Rust flakes can be carried by gasoline and clog the fuel filter, burden the fuel pump, and disrupt the carburetor or injector. Modern car tanks are generally coated with anti-rust layers, but the risk does not disappear completely. In plastic tanks, there is no rust, but water mixed with gasoline still disrupts combustion. - Gasoline aging.
Gasoline that is stored too long gradually changes its character and no longer burns as well as fresh gasoline. The effects are usually felt as the engine stuttering, reduced power, or difficulty starting. If gasoline has started to age, a full tank will not fix it.
Full Tank vs Empty Tank: Which is Safer?
A full tank is safer for rarely used cars, especially to prevent water and rust. Here is the comparison.
|
Aspect |
Full tank (around ¾ to full) |
Empty or low tank |
|---|---|---|
|
Air space in the tank |
Small |
Large |
|
Risk of condensation and water |
Low |
Higher |
|
Risk of rust on tank walls |
Lower |
Higher, especially at the bottom of the tank |
|
Fuel pump |
Submerged in gasoline |
Often exposed or operating with a thin layer of gasoline |
|
Gasoline evaporation |
Less |
Easier to evaporate |
|
Gasoline aging |
Still occurs in a full tank |
Still occurs with leftover gasoline |
|
Other risks |
Spills if filled to overflow |
Stalling due to running out of gasoline, indicator may be less accurate |
Cars that are rarely used should not be left with an almost empty fuel tank for a long time. The American Automobile Association (AAA) recommends that the fuel tank of unused vehicles be kept around three-quarters full or full to help reduce the air space that could experience condensation. Additionally, gasoline stored too long can degrade in quality. Nevertheless, the need for refueling should still be adjusted according to the duration of storage and the vehicle manufacturer's guidelines.
