While using a car regularly causes wear and tear on the engine, suspension, and other components, leaving a car unused without starting it can cause problems in itself.  

That’s right. Leaving a car unused can result in damage.  

If you stop driving your car for an extended period, you should be aware of the best practices to keep it safe. In this guide, we’ll examine how long you can leave a car without starting it and how to start a car that’s been sitting idle for months.  

Grab your keys, and let’s get going. 

What happens to your car if you don't use it?  

Wondering what happens if you don’t drive your car for six months? You’re not the only one. Here’s what to expect after storing a vehicle. 

Leaving a car to sit can cause damage and require the replacement of certain parts, such as:  

1. Tyres  

Rubber perishes with time and exposure to sunlight, even when not used. This is accelerated by the tyres having low pressure from a slow puncture or not being inflated regularly.   

If the tyres lose all their pressure, the sidewalls can crack, and the tyres develop a ‘flat spot’ in a matter of weeks, rendering the tyre too damaged to be used.   

2. Hoses  

Hoses are used in various systems in modern cars, including cooling, air conditioning, steering, and brakes. All rubber hoses deteriorate faster when not used, meaning leaks can develop in various places after a few months.  

3. Suspension Joints  

Along with hoses and tyres, many suspension and engine mount bushes are made of rubber, these also deteriorate faster when sat in the same position for a long time.   

4. Battery drain  

Various systems like the alarm, immobiliser and even some ECU functions still operate even when the car is not in use. This is known as a parasitic draw and is impossible to avoid completely. Without frequent use of the car, it can deplete the battery. 

How long can you leave a car without starting it?  

You should start your car’s engine at least once a week and let it run for half an hour. 

It would be ideal to drive the car for a short journey, too, as this would help keep the battery charged. This is a must if you’re not driving your car every day. 

How to keep the battery healthy in an unused car - three key steps 

There are a few things you can do to stop the battery from being damaged from lack of use, with the correct steps a battery can be kept unused for years.  

1. Remove the battery and store it  

Current draws from the car's electrical system, and temperature changes both affect the battery's health. Removing the battery from the car and keeping it inside, in a reasonably stable environment keeps the battery from deteriorating.  

Make sure to charge the battery fully before removing it, either by taking the car on a long drive or charging it using a battery charger. 

2. Trickle charging  

Most battery chargers have a trickle charge function. This keeps the battery topped up with a small amount of current constantly, preventing the battery fluids from crystallising and diminishing the battery's capacity.   

If you don't have a garage or the ability to get power to the vehicle where it's parked solar-powered trickle chargers can maintain a battery purely from solar power.  

3. Store the car in a cool and dry place 

Extreme weather conditions and temperatures can affect a car battery’s health. So, store the car in a cool and dry place like a garage. This protects the vehicle against temperature fluctuations and saves you money on damage. 

What happens to a car battery if unused? 

If you allow your car battery to become fully discharged for too long or too many times, it will no longer have the same capacity as before and may need replacing soon.  

When a car battery discharges, the liquids solidify into crystals inside the battery. When the battery is charged again, the crystals are dissolved, and the liquid enables the voltage potential to be restored, restoring the power in the cells.  

The problem comes when the battery is fully discharged too many times or for a long time. The crystals build up excessively and cannot be effectively liquidated, which severely limits the capacity of the battery.   

Different time periods can affect the car battery differently. Here’s a rundown on common concerns. 

What happens to a car if unused for 2 weeks? 

Modern cars should be okay left unused for two weeks.  

It’s not enough time for the tyres, other rubber components, suspension joints, and wiper blades to perish.   

Before parking, top up the tyre pressures and the battery charge—even just by taking the car on a long drive. Check that no interior lights or other electrical components are left on.  

What happens to a car if unused for a month? 

30 days of inactivity for a car could cause some issues, especially for older cars.  

The most likely issue is a dead battery. This can be mitigated by either disconnecting and removing the battery or using a trickle charger, as described previously.   

What happens to a car if unused for 6 months?  

The battery will almost certainly be flat and unable to recharge. 

Six months is quite a long time to leave a car unused. It is also likely that one or more of the tyres will have deflated. If a tyre has deflated, it will most likely need to be replaced, as the sidewall will have been stressed excessively at one point, causing cracking.  

Any fuel left in the car’s tank will likely have deteriorated to the point where the car will not run properly using it. 

What happens to a car if unused for a year or more?  

Even more issues occur after a year, such as rubber perishing. 

This may present itself in small leaks on coolant, vacuum or air conditioning hoses, and creaking/knocking suspension.   

To fix a car that has been left for over a year, it would probably need new tyres, some new suspension bushes, a new battery and a substantial inspection from a mechanic. 

Starting a car that has been sitting for 6 months 

If you need to start a car that’s been idle for six months or more, there are some extra checks you need to make for your safety. These include: 

• Inspecting the fluid 
• Check and charge the battery 
• Examine the tyres for rubber damage 
• Look for critters or animals under the wheels or undercarriage 

An overall service is always good if a car has been in storage.  

How to store a car for a long time - The conclusion 

Leaving your car for long periods isn’t advised, but sometimes, it has to happen. Ensure you store your car properly and run the engine when possible to keep it healthy. Finally, check if the car is healthy before driving it again. Double-checking is key here! 

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Author - Joseph Law

Joseph has been writing about cars for over seven years and writing for Bumper for over two, blending his passion for automobiles with a talent for storytelling.

Joseph has written about engineering and cars for Autozilla, Komaspec, and several engineering manufacturers. When he's not writing or tinkering with one of his five cars, Joseph dreams of owning an Alfa Romeo 33 Stradale.