If you’re like most people, your parents probably advised you that to always keep your gas tank at least ½ full in winter. On those days when the needle on the gauge drops low but you’re too tired to stop at the gas station, you may have wondered if it’s true. Unlike the myth that you need to warm up your car in winter…
Turns Out This One’s True!
In winter especially, you should try to keep that gas tank topped up, or at least half full. If your car runs on diesel fuel it’s particularly important.
The Problem is Condensation
Condensation occurs when colder water vapour comes into contact with a warmer surface. You can see this in action on your car windows on any frosty morning.
This can happen in your gas tank, because there’s air in any space in your gas tank not occupied by gasoline. Gasoline is relatively slow to warm up, and will help keep the air cool.
Just like drops of water forming on the side of a cold glass, drops of water can form on the inside walls of your gas tank, where they eventually slide down.
What Happens When there’s Water in Your Gas Tank?
Because gasoline and water don’t mix well, and water is heavier than gas, those beads of water that drop into your gasoline sink to the bottom. From there, they can:
- Be drawn into the engine and lead to corrosion.
- Lead to corrosion in the gas tank if it’s made of steel (many are plastic these days).
- If it’s cold enough, they can freeze in the fuel lines and prevent gasoline from reaching the engine. Your car could refuse to start or stall out.
You need a certain volume of air for the condensation to become a problem, so habitually running in the red can lead to more serious problems.
Other Reasons to Keep the Tank Half Full
There is also a safety reason: keeping your tank topped up means you have plenty of gasoline to help warm your car in case you get stranded by the side of the road. Hopefully you have a well-stocked car emergency kit that can help you stay safe too.
Mechanically, there’s another benefit to keeping the tank nice and full: a steady stream of gasoline helps keep your air pump cool. Water or ice particles will interfere with that, potentially leading to damage that can be expensive to repair.
But Someone Online Says it isn’t True
I’ll admit, this is a hotly debated topic online, and I’ve also read forum posts and blog articles from people who say they always let their gas level fall and they’ve never had a problem.
And those people aren’t lying – but you have to look at their location. Many of these people are posting from the southern half of the US, or even the northern half where their winters aren’t as cold as ours. Most Canadian vehicle manuals will actually recommend it.
Yes, it’s also true that modern cars are designed differently, and that modern fuel injection systems don’t have low pressure areas or potential gaps where air con collect. But neither of those things prevent water from condensing in the gas tank in the first place.
What About Ethanol?
It’s true, Canadian law says there needs to be at least 5% ethanol in our gasoline, and ethanol is like antifreeze in that it freezes at a much lower temperature. While ethanol can help, it can’t stop condensation from happening, or prevent it from reaching your fuel lines.
Keep Your Tank as Full as Possible
No matter what time of year it is, try and keep your gas tank as full as possible. When you refill, choose a gas station with a lot of customers. The steady stream of customers means it’s more likely that the station is refilling its massive storage tank more often too. Don’t forget to close up the gas cap tightly when you’re done.
For this reason, it’s not advisable to store gasoline for longer than a few months, and if you have any kind of outboard motor, it should be drained for storage.
More Tips for Winter Driving
FAQs
More so than ever during the winter months, it's crucial to keep your gas tank topped up on the regular. This is because extremely cold temperatures can cause your car's fuel lines to freeze. As a result, your car may stall or not start at all.
Should you keep a full tank of gas in the winter? ›
Keep your vehicle's gas tank at least half full in the winter. The main reason is the weather. What happens in a heavy snowstorm as you're driving home from work? Traffic slows to a crawl.
How much gas should I have in my tank in the winter? ›
Since you can't control the ethanol content or how your vehicle's engine will respond to it, the best way to minimize condensation and avoid problems caused by freezing fuel lines is to keep your tank more than half full in the winter.
Is it bad to have an empty gas tank in freezing weather? ›
Experts suggest keeping your gas tank at least half full in the winter to avoid major damage. Cold temperatures can cause condensation to form on the walls of a gas tank that is running low. Water will drip into the gas and eventually sink to the bottom.
Is it better to always keep your gas tank full? ›
Engine Health
Running your vehicle on a consistently low fuel level can lead to sediment and debris from the bottom of the fuel tank being drawn into the engine. Over time, this can affect your engine's performance and potentially cause damage.
Is it bad to be low on gas in the winter? ›
Our advice: If you live in an area with extremely cold winters, it's a good practice to keep your gas tank at least half full during the coldest months. This helps to reduce the amount of air in the tank, which can minimize condensation and the potential for water to freeze and cause fuel line blockages.
How cold is too cold for gas? ›
This depends on the type gasoline and its components. Different elements of the fuel are made from unique molecules, which will become more solid at different times. You could probably give it a range of about -40 and -200 degrees Fahrenheit, with most of it freezing at -100 degrees.
How to keep a gas tank from freezing? ›
Keep the Gas Tank Full
It also plays a critical role in minimizing the amount of air—and consequently, moisture—inside your tank, reducing the chances of water condensation. Less condensation means a lower risk of water freezing within your fuel lines.
How much gas do you need in your tank for it not to freeze? ›
Many experts recommend that prior to large, frigid temperature drops, drivers fill their gas tanks to at least halfway full. While it's nearly impossible for the gas inside your tank to freeze, the air left inside your gas tank has moisture in it.
Is it better to store a car with a full tank of gas or empty? ›
Choose a clean, dry garage or storage facility, as damp air can cause rusting. Ideally, store your car in a climate-controlled facility. Fill the gas tank completely full. An empty or low gas tank will lead to internal rust as condensation and moisture builds within the tank.
Naturally, sediments sink to the bottom of your fuel tank, so running on empty means your filter could be getting clogged with dirty fuel. Your fuel filter may even become completely blocked in some cases. The most obvious risk you take when ignoring your fuel light is, of course, running out of fuel.
Can you leave gas tank outside in winter? ›
Even as the temperatures drop, your propane tank should remain outdoors. Propane tanks should always be kept in a well-ventilated, shaded area and at least 10 feet from your home. Turn it off. If you'll be bringing your grill inside for the winter, be sure to turn off your propane tank and disconnect it.
How much gas should I keep in my car in the winter? ›
Before any long-term storage, it's a good idea to fill your vehicle's fuel tank all the way to the top. This dramatically reduces the potential for condensation to form either inside the tank itself or the fuel lines leading to the engine—if moisture collects, it can result in significant fuel-system corrosion.
Why is it bad to not fill your gas tank? ›
An almost-dry tank can leave you stranded and potentially damage your vehicle. QuickTakes: Fuel pump damage. Fuel filter clogs.
What wastes the most gas in a car? ›
- Driving fast increases drag, which increases fuel consumption. - Braking excessively wastes gas. - Turn off your vehicle you are waiting, excess idling is a major waste of gas. - Remove unneeded car racks and carriers.
Is it better to store a car with a full tank of gas? ›
Choose a clean, dry garage or storage facility, as damp air can cause rusting. Ideally, store your car in a climate-controlled facility. Fill the gas tank completely full. An empty or low gas tank will lead to internal rust as condensation and moisture builds within the tank.
Can you store gas over the winter? ›
Always store your cylinder gas outdoors, even in the winter
Storing your tank inside can also cause dangerous temperature changes within the tank. The freezing temperatures of cold winter months do not reach temperatures low enough to affect gas that is stored in cylinders.
How often do you need a full tank of gas? ›
The less fuel in your tank, the greater the risk of running out completely in a bad spot. While different experts have different suggestions, it's typically agreed that drivers should refuel their vehicle when they have anywhere between a quarter of a tank or half of a tank left for maximum efficiency.
