What Happens if You Put RV Antifreeze in a Car

Couple on a white and yellow RV

Antifreeze is antifreeze, so why bother with instructions in the small print? Because much can go wrong, even dangerously wrong. Many people – maybe you, too – dream about vacations in a motorhome and, given an opportunity,  you may rent one. Under some circumstances, you may need to pour antifreeze into the engine. Driving an RV, you may use the RV antifreeze – and you can kill the engine within a few miles.

Much worse, you may pour automotive antifreeze into the plumbing and possibly fatally poison yourself. Be careful with the antifreeze, and make sure you enjoy the motorhome vacation.

RV Antifreeze is made for pipes on campers, RV’s, and houseboats. Adding RV antifreeze into a car’s system could be sure death for your car engine as this stuff has no anti-boiling agents. Given that it’s only antifreeze, your engine would be at risk of overheating and warping.

On the other hand, mixing it in with real antifreeze would turn it to gel and create a huge mess. The one that would also create hot spots, maybe even clog your heater core. In this article, we cover this theme and much more to help you understand the proper use of RV antifreeze.

RV Antifreeze Is For The Plumbing, Not The Engine

Who doesn’t love being on the road? Passing through unknown cities, passing beautiful lakes and crossing mountains as you move along, meeting new people wherever you stop. Some do it by taking a bus or a train; others ride a motorcycle, even a bicycle. The majority probably does it in a car. A growing community of travelers, however, does it in a motor home.

Like any vehicle with an engine, a motorhome requires different liquids to run: fuel, lubricants, antifreeze, even the water for windshield vipers. But a motorhome has an additional system: plumbing. With water in the pipes, protection is necessary against freezing when you expose an RV to freezing temperatures. That’s the role of the RV antifreeze.

Is it the same type as the one you pour into the engine to stop it from overheating and freezing? No, it isn’t. And what happens when you use the so-called RV (recreational vehicle) antifreeze for the engine?

First Things First – What is Antifreeze?

The crucial difference between the car (engine) antifreeze and its RV counterpart is the toxicity. The engine antifreeze is highly toxic to humans and animals alike. RV antifreeze, on the other hand, is far less harmful and is dangerous only concentrated.

There are other essential differences. But first of all, let’s see what is antifreeze, in general? It is a liquid you use to lower the freezing temperature of the water.  Most antifreeze solutions also raise the boiling point of water. So, in essence, you use antifreeze to keep water in a liquid state.

When combined with water, concentrated antifreeze becomes what is commonly known as coolant. Antifreeze is frequently pre-diluted. The concentration of the antifreeze in the water determines the freezing/boiling range.

Chemicals You Can Find in Antifreeze

Most RV antifreeze solutions have ethanol or propylene as the base ingredient.

  • Ethanol-based antifreeze doesn’t hike the boiling point, so it only prevents freezing.
  • Propylene-based antifreeze will both raise the boiling point and lower the freezing point. Both types come in concentrate and pre-mixed. The former must be diluted with distilled water before use, and the latter is used out of the container.
  • These, along with the rest of the ingredients, are both non-toxic materials. That makes them non-harmful to humans and animals in small doses.

Most automotive antifreeze types are ethylene-glycol-based. It is odorless and has a sweetish taste.

  • This type of antifreeze is extremely toxic. It must not be ingested and must remain out of reach of children and pets.
  • Unlike RV antifreeze, which is (almost) always pink, car antifreeze comes in various colors, depending on the chemical composition.

Car Antifreeze Isn’t the Same as RV Antifreeze

So how RV antifreeze differs from car antifreeze? Both kinds have the same purpose but play very different roles. It can be unclear to a new motorhome user, which needs both automotive and RV antifreeze.

Automotive or engine antifreeze prevents the water in the engine cooling system from icing and from boiling.

The antifreeze should be dissolved in distilled water – tap water contains minerals that could crystalize or calcify and hamper the flow or damage the pump. The ratio is designated adapted to the temperature range in which the engine operates. The coolant also inhibits corrosion, which pure water would over time cause in the motor.

The coolant runs in a sealed system comprising the radiator, the container, hoses, and channels in the engine block.

When the motor is running, a pump pushes the coolant through the entire system. It absorbs heat in the engine and releases it through the radiator. The coolant boils at a higher point than pure water, essentially allowing the car to work harder.

In cold weather, it stops the water from freezing in the engine. Trying to start the car with the coolant frozen solid in the motor may block the water pump and cause massive damage – the best scenario is burning the belt drive. The worst includes many bent parts an astronomical repair bill.

Motorhomes Also Use Motor Antifreeze – In The Engine

To make it clear, an RV also has an engine that requires the coolant, the same as any other motor vehicle. Naturally, it goes into the motor, in the summer and winter alike. The RV antifreeze comes into play only in the freezing weather.

An RV has systems regular vehicles don’t have. For instance, it has plumbing. It is a car with an apartment in the back and on top. Adding to the comfort, inside are a kitchen, a toilet, and a shower.

Its plumbing connects the water tank with faucets, the shower, and the toilet. It also leads the so-called gray water, from the sink and the shower, into one tank. The sewage from the toilet, adequately called black water, flushes into a sealed sewer tank.

Winterizing the RV With Antifreeze

In the winter, the RV plumbing water may freeze and damage the pipes and the pump. Repairs are costly and time-consuming. To avoid that, RV owners should prepare their vehicle for winter – winterize it.

Winterizing consists of several checklist measures, including draining the reservoirs, pouring the adequate amount of antifreeze, and pumping it into the entire plumbing system. Unlike automotive antifreeze, RV antifreeze has a broader range of applications, primarily to protect the plumbing lines and water tank from ice formation. So far, we can see that automotive and RV antifreeze solutions have many differences. But there’s more.

What happens when you mix RV and car antifreeze?

Those are the fundamental differences between RV and car antifreeze. But, finally, what happens when you mix them up?

While not as poisonous as engine coolant, RV antifreeze should also not be ingested. If you have it in your camper’s tank, don’t drink that water. After you drain and flush, though, the water from the tank will be safe for consumption. The RV antifreeze residue in the tank and the pipes will not be harmful.

However, what if you make a mistake and pour engine coolant into the system? You’ll need to flush it out thoroughly to avoid the threat of poisoning someone. It means you’ll have to flush the system out repeatedly.

Even better, connect your RV water intake with a garden hose and flush through open taps. Then dissolve a container of baking soda and refill, let the solution sit for a couple of hours. After another flushing, the water in the tank should be clean. But if it tastes even slightly sweet, repeat the process. Remember – engine antifreeze is poisonous.

RV at night

Motorhomes are a frequent rental option, so perhaps some users may become confused in an emergency and pour the RV antifreeze into the engine. Well, the liquid in the cooling system won’t freeze, that’s for sure. But the engine may overheat, and that could lead to warping and total engine damage.

It is maybe even worse if you top-up the coolant with RV antifreeze. The two compounds may chemically react and form a gelatinous substance that will not perform the cooling function. So, if you pour the RV antifreeze into the engine, you need to flush it immediately.

The problem is, of course, that it’s a job for a mechanic. In case one is out of reach, drive on as slowly as possible and keep a close eye on the temperature gauge. A dysfunctional cooling system can overheat within a few miles.

The best way to avert any mistakes: unless you’re very sure of what product you’re using for what – ask for advice or carefully read the instructions. The last thing you want is to harm your engine, right?

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