Can Engine Oil Freeze? Here's What Happens In Cold Weather

When you think about the various moving liquids of your car, there's a certain related issue that may spring to mind in the winter season: the possibility of freezing. We've all seen a puddle of water solidify into a sheet of ice when it's cold out, so traditional logic dictates that a similar solidification could occur to your car's various liquid components.

Take, for example, the oil in your car's engine. It's the oil's job to keep your engine's various components lubricated and friction-free. If that oil were to completely solidify, you can probably imagine the unpleasant effects that would befall your car. The good news is that the odds of your engine's oil solidifying completely are extremely low. The bad news is that engine oil doesn't need to solidify completely to start causing dangerous knock-on effects to your engine and your car's overall operation. Remember, a puddle of water doesn't need to be more than slush to start being dangerous.

Compared to some other liquid and semi-liquid substances, oil has a much lower freezing point. The only way for a container's worth of oil to completely freeze into a solid mass would be if the ambient temperature reached around -320 degrees Fahrenheit. That's several magnitudes colder than the coldest plateaus of Antarctica, so if your engine oil ever froze completely, you'd probably already be a popsicle yourself.

That said, while engine oil doesn't freeze completely, cold temperatures can cause it to become thick and sludge-like in its consistency. Starting at temperatures of around -4 degrees Fahrenheit, engine oil starts to become clumpy and slow-flowing. It's still technically a liquid at this point, but rather than the slick and slippery substance you need it to be, it's more akin to something like honey or molasses. If you tried to funnel honey through a bunch of tight metal nooks, to say it would take all day would be an understatement, and that's definitely not workable when you're in the middle of a drive.

Normally, when you start up your car, the oil starts flowing through the engine components right away. This ensures that all of those rapidly-moving parts get a proper dose of lubrication and can continue their work without damage or overheating. If the oil becomes thick from the cold, though, it won't flow nearly as quickly as it's supposed to. The components of your engine will already be spinning up before the oil even has a chance to reach them. If the oil doesn't get there in time, the components will start grinding up against each other with heightened friction, subjecting them to potentially intense physical damage. It's a similar effect to when oil gets too hot and evaporates.

Even putting that aside, without the extra lubrication from the oil, your engine will have to work much harder to draw in fuel from the intake, which will severely worsen your car's overall fuel economy. Thickened oil can also lead to air build-ups in the line, which can mess with your overall oil pressure. All of this adds up to damaged parts and expensive repairs.

While you only really have to worry about oil becoming thick in a particularly bitter winter, that doesn't mean the problem is completely eliminated. If you attempted to operate your car with the oil in this state, it could result in serious, lasting damage.

If you live in cold conditions, the best thing you can do for your car's oil, not to mention its overall health, is keep it stored in an insulated and/or heated garage when not in use. Besides that, consider switching to a synthetic engine oil rather than a conventional oil. Synthetic oils with higher viscosity indexes are more resistant against being thickened by the cold, so even if it's chilly out, they should still flow properly. Synthetic oils are also a bit smoother in composition, as opposed to conventional oils that may contain cold-vulnerable substance deposits.

Before you make any changes to your car's oil, make sure to check your owner's manual for supported oil types, and to consult a mechanic.