Combustion-engined vehicles rely on a number of vital fluids. You need good fuel, good oil to keep the engine lubricated, and good coolant to keep the engine from overheating and seizing up. Or, you know, you could just use a few bottles of Pepsi. Wait, what?
This madcap experiment comes to us from Garbage Time. It’s an Australian YouTube channel about cheap old cars—known as “nuggets”—and doing silly things with them. You might know the host better as tech Youtuber Dankpods, but his infectious mannerisms have translated well to the world of automotive tomfoolery, too.
Don’t worry—as ridiculous as this sounds, we’re going to dig deep. We’re looking at how Pepsi performs as a coolant on both short-term and long-term timescales. This is the real consumer advice you need. Read on.
Is Pepsi Okay?
A used 2009 Proton Saga served as the mule for this test. Known as the S16 in Australia, it was the cheapest car on the local market in 2009. Retailing for just $11,990, you got a 1.6-liter four-cylinder engine for your money with 110 wild horses under the hood. But could those horses survive on Pepsi?
The experiment was ultimately a straightforward one. The coolant was drained, and replaced with the fizzy soft drink that has always wanted to be Coke. This wasn’t as easy as you might think, as the Pespi fizzed up a great deal during the filling process.
With a few liters of Pespi in the cooling system, the Proton had its engine started, and the torture began. It took some time to get things up to temperature, but after a good while, the thermostat was open and the Pepsi was circulating.
At this point, you might have expected calamity in short order. Surely the sugary Pepsi would caramelize and clog up the cooling channels. Or perhaps all the carbon dioxide in the soft drink would cause an air bubble precipitating the end. Surely the engine would overheat before long!
And yet, it soldiered on. The temperature gauge rose as per normal, and the Pepsi cooled the engine without complaint. Even hours of drive tests weren’t enough for the Malaysian donk to give up the ghost. So what gives?
Well, as it turns out, Pepsi is a fine choice of engine coolant, under very specific circumstances. That might sound wild, but here’s the thing—Pepsi is, by and large, mostly just water. And water cools engines really well! Fundamentally, if you put a bunch of water in your engine’s cooling system, it’ll run all day. Using Pepsi instead just isn’t that much different.
The carbonation doesn’t really cause problems, either. The solubility of carbon dioxide in the fluid reduces significantly at high temperatures. Thus, as the Pepsi heats up, the bubbles come out of solution quite quickly, and would be quite easy to burp out of the system. There’s a benefit to the sugar in Pepsi, too. Solutions of sugar and water have an elevated boiling point, something which is beneficial in a cooling fluid.
Plus, Pepsi is cheap! A gallon of premix coolant costs around $18.95. You can get over a gallon of Pepsi for less than $5. Winning, right?
“But we don’t use water as coolant!” you cry. “And Pepsi has to be bad!” Hold on, hold on. I’m getting there.
Fundamentally, you’re on the money. But let’s start with water. There are two prime reasons we don’t use water as coolant. The first is freezing point—if water freezes inside your engine’s cooling channels, it’s almost certainly going to do damage. Hence why coolant is commonly referred to as “antifreeze,” as it contains agents to lower its freezing temperature. Secondly, running plain water can lead to corrosion over time. This can cause leaks or clogs as corrosion byproducts build up in cooling channels.
For both of those reasons, you shouldn’t actually use Pepsi as an engine coolant. It’s probably worse for your engine than water, given that it’s slightly acidic. This shit can clean coins, so it’ll gladly start chewing away at metals in your cooling system. It’ll also freeze fairly easily if you live in a colder area.
What does this mean? Well, if you’re in an emergency situation with no coolant and you really just need to keep the engine going for a few hours, Pepsi will do the trick. However, it’s bad for your engine, and you’d want to get it out of there quickly to avoid corrosion. I’ve seen straight tap water clog a brand new radiator in a year flat. I’d suspect Pepsi would do the same in months, if not weeks.
But what about the sugar? Will it cook inside the hot engine, and clog things up? That’s an interesting question. On the one hand, it’s commonly said that sugar caramelizes at around 320 °F. Meanwhile, the average engine thermostat is set somewhere around 195 to 220 °F. Under the 15 psi of pressure inside the cooling system, the boiling point of water raises, too, so it’s unlikely to start boiling until around 248 °F or above. 50:50 coolant mixes raise this to 265 F, because ethylene glycol coolant has a higher boiling point than water.
Based on those numbers, it seems unlikely the sugars would caramelize too easily. This is also borne out later in the video, when boiling Pepsi in a kettle actually goes relatively cleanly, with no sticky residues spotted.
However, there are some reports that caramelization can happen at lower temperatures on a longer time scale, so I wouldn’t trust the Pepsi in there for long. Plus, there’s a side risk here. If you’re running Pepsi as coolant and you have some kind of leak, that could cause all kinds of trouble. If it’s seeping past the head gasket, the coolant would absolutely boil and leave sticky deposits everywhere inside the engine. Similarly, if it’s dripping out of a pipe on to a hot exhaust or oil pan, that’s going to be an ugly mess, too.
So, what’s the upshot here? Well, Pepsi is mostly water. Thus, you can pour it in your radiator and your car will work surprisingly fine. At the same time, it will be eating away at your engine and you really shouldn’t do this unless you absolutely really have to. Hope that helps! As always, stay milky.
Image credits: Garbage Time via YouTube Screenshot, Walmart, Lewin Day