Keep Cool: Why You Should Be Paying More Attention To Your Coolant

Troy Siahaan
by Troy Siahaan

Not all coolants are created equal

We talk all the time about how fun motorcycling is. It’s true, obviously, but a good ride starts with a good motorcycle, and a good motorcycle is one that is properly maintained. One area often neglected is the motorcycle’s cooling system. Now, if you have an air-cooled engine in your bike, there’s no reason to continue reading. This article isn’t for you.

But if you’re one of the many people with a liquid-cooled engine, read on. You may or may not have known that coolant in your engine should be flushed periodically. Some manufacturers also specify the kind of coolant to use, too. Then what should you do if you live or ride somewhere that has freezing temperatures at night or extremely hot temps during the day?

The nuances of a liquid-cooled engine are quite complex, but you don’t need to worry about all of them right now. There are a few basic principles to keep in mind that will cover most of what you need to know to keep your motorcycle happy for miles to come.

First Off: The Purpose of Coolant

This seems obvious at first. Clearly, coolant is used to keep a liquid-cooled engine, well, cool. Technically this is true, as the liquid carries heat produced from the engine to the radiator, and air flowing through the radiator – whether from forward motion or from fans – takes the heat away.

Beyond its primary purpose, coolants also help protect your engine when it’s freezing by not freezing up itself and remaining in its liquid form below 0ºC/32ºF. The fact your engine’s cooling system is pressurized also enables a lower freezing point. But when the engine is off, none of that matters. If you had just water in the system it would freeze, causing expensive, and sometimes irreparable, damage to your engine. Coolant that remains a liquid in freezing temps can literally save your engine.

Lastly, coolant can also contain additives to help your cooling system stay clean and healthy for longer.

Propylene Glycol vs. Ethylene Glycol

Glycol is what keeps the liquid (water in this case) from freezing over. Interestingly, the marriage between water and glycol also raises its boiling point beyond water’s normal boiling point of 100ºC/212ºF. This combined with the pressure produced from the radiator cap is why the coolant in your system doesn’t blow over on hot days.

The Bel Ray Moto Chill coolant uses propylene glycol, though you’d need to carefully examine the back of the bottle to know that.

There are two main types of coolant available today: propylene glycol and ethylene glycol. While they sound a lot alike, there are some significant differences between the two. The biggest one is this: Ethylene glycol is extremely toxic and can kill you if ingested, even in small doses. Propylene glycol won’t kill you, but you still shouldn’t drink it.

Toxicity levels aside, both kinds of coolant exist for a reason. They have different thermal capacities and properties, which offer different benefits. Since we doubt you’re actually going to drink your coolant, we’ll stick to our usual recommendation and suggest you use whatever coolant your owner’s manual calls for. The exception to this rule depends on whether you plan to take your motorcycle onto a closed course. Then you should stick to water and a non-glycol blend. More on that below in the water section.

Can I Mix The Two?

In short, no. Absolutely not. Mixing the two different types of coolant runs the risk of prematurely wearing out your water pump, could cause premature corrosion, and/or make your engine run hotter than it should. This is one of the reasons why coolants are different colors – so you don’t mix them up. Though this isn’t standardized practice among coolant manufacturers, so one brand’s green coolant may or may not be the same as another brand’s orange coolant, for example. This uncertainty is why you shouldn’t mix coolants unless you’re absolutely sure the two types are 100% the same.

If you’re low and need to add more, it’s much safer to add distilled water (otherwise known as demineralized or deionized water. It’s all the same) and then flush the system and refill at your earliest opportunity.

Photo: CGN089/

Also, stay clear of coolants with silicates or phosphates. These can form layers over the metals in your cooling system which traps the heat the coolant is trying to get rid of in the first place. This isn’t such a big deal if your coolant system is regularly and routinely flushed. The bigger issue with silicates and phosphates is that they can prematurely degrade the seals in your water pump. So it’s best to just stay away. You don’t really have to worry about this with most, if not all, motorcycle-specific coolants. But if you find yourself staring at random coolants in a gas station someday because you have an emergency, it’s something to keep in mind.

As always when it comes to what you should and should not put into your motorcycle, refer to your owner’s manual. Nobody knows better than the people who made your bike to begin with.

What About Water?

Photo: Benjamin Clapp/

Water – distilled water, to be precise – is a great conductor of heat and has a great thermal capacity, too. The problem is it freezes and boils at relatively low temperatures. If you can keep your engine away from those temps and flush it often to keep the contaminants and impurities to a minimum, you actually can run it as a coolant. In fact, this is exactly what they do with a lot of track-specific motorcycles. Distilled water is relatively cheap compared to standard coolants, works great for this specific use case, and gets flushed regularly so the cooling system is never dirty.

And there’s one more benefit to straight water – there’s no glycol. Yes, we said glycol was great for expanding water’s freezing and boiling points, but it’s also extremely slippery and hard to clean up. In track environments, glycol on the ground poses a major safety risk for anyone who happens to ride over it as it’s really slick.

In the case of your average road bike, the benefits of distilled water still apply. However, for the sake of everyday convenience and keeping your bike in its proper operating range over wide temperature variances, just use the recommended coolant and/or water-to-coolant ratio.

Lastly, stay clear of tap water. The minerals added to tap water can cause havoc on your cooling system over time. But if you’re absolutely in a pinch with no other options, then go ahead and use it. Just flush it out as soon as you can.

Final Tips

Like most motorcycle maintenance tips, consistency is key. A good rule of thumb is to change your coolant once a year, depending on how much you ride. Coolant does have a shelf life, so even if you don’t ride much, it’s still a good idea to flush it out periodically.

Another thing to keep in mind: Some manufacturers have their own labeled coolant, just like they have their own labeled oil. While it’s safe to use these on your motorcycle, you don’t have to. Sometimes these labeled bottles are simply more expensive versions of the generic bottles sitting next to it on the shelf. Above all, be sure to check if the type of coolant is compatible with your motorcycle.

Coolants We Like

Different coolants exist for different reasons. The nice thing about coolants is that one type can work for a variety of bikes and riding styles. Unlike, say, tires that have become so specific and perfected for one type of riding.

Propylene glycol coolant: Bel Ray Moto Chill Racing Coolant - Non-toxic, pre-diluted, and ready to use, Bel Ray Moto Chill offers corrosion protection and is formulated for high-performance (read high heat) conditions. However, its glycol content means it’s not legal for racetrack use.

Ethylene glycol coolant: Maxima Coolanol Coolant - A ready-to-use 50/50 blend of ethylene glycol antifreeze and deionized water, it provides optimum rust and corrosion protection for all aluminum and magnesium motorcycle and ATV liquid cooled engines. Coolanol also contains anti-foam agents to reduce water pump cavitation and increase cooling capacity. Coolanol 50/50 blend protects from freeze-ups in winter down to -34°F. Not legal for track use due to its glycol content.

Race-legal coolant (and street-legal too): Engine Ice High Performance Coolant - Biodegradable, phosphate free and non-toxic, Engine Ice reduces operating race temperatures and effectively keeps boil over temperatures to 256°F or less and freeze-up protection down to -7°F. Engine Ice is popular (and legal) in the racing community because it doesn’t contain glycol and yet delivers great coolant properties.

A versatile coolant: Red Line SuperCool Engine Coolant with WaterWetter - Red Line is the name when it comes to race-oriented coolants. One of its most well known products, WaterWetter is legendary in the track community for its cooling properties and glycol-free makeup – but you have to mix it with water before adding it to your application. Red Line SuperCool is already premixed with WaterWetter, distilled water, and other agents, including ethylene glycol, making it illegal for track use. SuperCool not only reduces rust, corrosion and electrolysis, but it also cleans and lubricates water pump seals. Crucially, it’s compatible with all antifreeze and coolant types, and can even improve the heat transfer of both types of coolant.

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Troy Siahaan
Troy Siahaan

Troy's been riding motorcycles and writing about them since 2006, getting his start at Rider Magazine. From there, he moved to Sport Rider Magazine before finally landing at in 2011. A lifelong gearhead who didn't fully immerse himself in motorcycles until his teenage years, Troy's interests have always been in technology, performance, and going fast. Naturally, racing was the perfect avenue to combine all three. Troy has been racing nearly as long as he's been riding and has competed at the AMA national level. He's also won multiple club races throughout the country, culminating in a Utah Sport Bike Association championship in 2011. He has been invited as a guest instructor for the Yamaha Champions Riding School, and when he's not out riding, he's either wrenching on bikes or watching MotoGP.

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  • Tech Tech on Aug 12, 2023

    There are plenty of coolant types: SI-OAT, IAT, OAT, HOAT, P-HOAT, etc. All explained in Valvolines article on coolants. I use the BMW coolant which is nothing but Zerex G48 in the motorcycle and Zerex G40 in the car.