Here’s Which Diesel Anti-Freezing Additives Won’t Leave Your Truck Stranded This Winter: Project Farm

Diesel technology remains a great way to get a fine mix of fuel economy and power, especially when the diesel engine is found under the hood of a pickup truck. However, diesel fuel is a lot weirder than gasoline and if you don’t treat your tank of diesel in the winter, you can find yourself with a truckload of gelled fuel that can’t be pumped into your engine. Thankfully, lots of companies have come to the rescue with products designed to keep diesel engines running better in the winter. But which brand is the best? It’s time for one of our favorite YouTube channels, Project Farm, to put diesel additives to the test.

If you’ve never driven a diesel vehicle before this may seem foreign to you. A car powered by gasoline may struggle to start when it’s 0 degrees Fahrenheit outside, but the gasoline in your tank will almost certainly still be liquid. Diesels have a much harder time in the same conditions.

Gasoline and diesel fuels work differently. Gasoline engines use spark plugs to ignite the fuel/air mixture. With each fresh charge of fuel and air, a spark jumps across the plug’s gap to ignite the mixture. As you can see in the animation below, a diesel engine appears to operate like a gas engine at first glance: the fuel/air mixture enters the combustion chamber through the intake valve, and once combusted, exits via the exhaust valve.

But you’ll note there’s no spark plug in the animation, because diesel fuel is not ignited by a spark. Instead, the piston highly compresses the fuel/air mixture at the top of the stroke, and this high compression heats the mixture enough to ignite it. This is why diesel engines are called compression ignition engines: They ignite the fuel/air mixture via compression rather than with a spark from a plug.

Now, diesels do have electric plugs, but they are glow plugs, not spark plugs. Glow plugs warm the cylinders to aid ignition when the engine is cold, but once running, the fuel/air mixture is ignited solely by compression. Heck, if you stuck an open flame to untreated diesel fuel, you’d find it hard to actually get it to ignite. Look, don’t ask what I do during the summer (or try this at home).

However, despite this technology, the glow plugs aren’t going to help much if you can’t get fuel to the engine. Diesel fuel is made out of a complex mix of hydrocarbons, but for the purposes of this piece, what matters to us is the paraffin wax contained in diesel fuel. In cold weather, these waxes thicken and crystalize, giving your diesel fuel a consistency like honey. That alone is bad as your pumps can struggle to get the goo to the engine. That can cause engine stuttering and in a worst-case scenario, stalling. In seriously sub-zero conditions, your diesel fuel can freeze into a solid. Your diesel car, truck, or piece of equipment has no chance of starting in that state.

This process is called “gelling” and the exact temperature it starts to happen can vary. Technically, diesel can begin gelling at around freezing temperature, or 32 degrees. However, most consumers won’t be hit from the effects until you’re closer to about 10 to 15 degrees or so. Biodiesel blends are known to thicken at higher temperatures.

Thankfully, modern chemical science means that there is a way to battle gelling. You can buy bottles of additives to dump into your diesel tank that lowers the freezing point of your diesel fuel. In theory, your worries of gelling will be a thing of the past.

Now, putting a bottle of something in your tank to improve the performance of something sounds like snake oil. However, anti-gel is one of those products that does exactly as it says on the sticker. You can even buy a diesel de-icing fluid. Some of these products also make grand claims about improved engine performance as well as enhanced lubrication. Who else than the wonderful host of Project Farm to put these claims to the test.

As a fan of diesel power, I’m familiar with using these products. I used to drive around with several bottles of Hot Shot’s Secret in the backs of my diesels ready to dump in when it was time to get fuel. I’ve always wondered which anti-gel additive was the best.

This Project Farm showdown included diesel anti-gel and diesel de-icing potions from Hot Shot’s, PEAK, Power Service Diesel, Amsoil, Archoil, STA-BIL, Optilube, Howes, Stanadyne, Ford, and Lucas. I loved this selection because you will find most of these brands at pretty much any gas station or truck stop during wintertime. I also dig the addition of the Ford-branded stuff. Is OEM-branded anti-gel any better than the stuff at the gas station?

Personally, of the lineup, I’ve used Howes Diesel Treat, some off-brand additive I’ve found somewhere, and Hot Shot’s Secret Diesel Winter Anti-Gel. In my personal experience, my car always started quicker and with a bit more exuberance when treated with the Hot Shot’s than with the Howes or the generic. But those were just feels and a sample size of a handful of cars. Were my feels even close to being on point?

Our charismatic host begins by telling us the battery of tests he’s going to put the fluids through. The first test is simple enough. Mason jars filled with diesel will get the proper dose of anti-gel and put into a deep freeze, where a winner should be clear. Then, diesel fuel will be put into a sort of opposite test where the emergency de-icing fluids will get a chance to melt frozen diesel.

The other tests cover the bonus features advertised by these products, including fuel system corrosion protection, lubricity, water dispersants, and whether they really do increase the base fuel’s cetane number. The cetane value refers to the combustion speed of the diesel fuel and the compression required to ignite it – the higher the cetane number, the better the fuel’s combustion performance. While these extra features aren’t necessary to keep diesel as a liquid, it’s nice to have some extra benefits.

Something great about Project Farm’s tests is that the host includes a control and often, he’ll toss in a sort of backyard hack. In this case, two-stroke oil is tossed into the mix.

Project Farm starts off the test with untreated diesel. Unsurprisingly, the untreated diesel was the worst performer in the lubricity test and it couldn’t stand up to the bitter cold. I mean, that’s why these additives exist in the first place. The host explains that the process used to reduce the sulfur content in diesel has the unfortunate consequence of also reducing diesel fuel’s lubricity. So, in the lubricity test, which involves some metal-on-metal action, diesel fuel does little to prevent damage. This can simulate the moving parts in your fuel system, which are generally cooled and lubricated with fuel.

A surprising result in this first test was the Lucas anti-gel. A lot of folks use Lucas products. I use them, my wife uses them, and our parents did as well. Yet, the Lucas was no better with lubrication than untreated diesel. However, as Project Farm notes, Lucas didn’t promise any increase in lubrication. Howes advertises increased lubricity and does so with a colorful picture, but delivered only slightly better lubricity than the Lucas additive and the control, with a ton of damage caused to the test media. As someone who used to depend on Howes for my diesel vehicles, that was disappointing.

I won’t spoil the whole test here and you should watch it yourself. Archoil won the lubricity test after causing relatively minimal damage to the test piece. Hot Shot’s finished second with an almost imperceptible larger swath of damage. The most amusing performance was the two-stroke oil. In the lubricity test, it performed better than most of the anti-gel additives, even the ones that claimed to increase lubricity.

Another highly interesting test was the main showdown to determine which anti-gels actually prevented gelling. Surprisingly, the Lucas and Stanadyne anti-gels completely failed, and their fuel examples froze solid. Unsurprisingly, the two-stroke oil did nothing. Peak and Hot Shot’s came out on top with fuel that remained the most liquid. From there, the gauntlet of tests included rust prevention, water dispersal, emergency de-icing, and increases in cetane. Hot Shot’s won most of these tests with Lucas putting in a sad performance, finishing in last place in every test.

In the end, the tests concluded with Hot Shot’s earning a decisive win, performing measurably better at everything than even second place, which was Peak. That’s impressive given Hot Shot’s affordable $17 price, which was about half the price of a handful of the other options.

So, what did we learn here? There are lots of different diesel anti-gels out there, many of which are from storied brands. However, some performed so poorly at their one job that there’s a non-zero chance your diesel engine might not start if you’re using that particular fluid as diesel treatment. Unfortunately, Lucas was the worst performer in the entire test. It didn’t keep the diesel from freezing, didn’t do much better when the dose was doubled, and performed the worst when it came to upping cetane, preventing corrosion, and upping lubricity.

In other words, you should always check reviews and tests of products, including ones by popular name brands. You never know if a brand known for making good products creates something that’s far behind the rest of the pack.

One thing is for sure, diesel anti-gel isn’t snake oil! As always, if you want to learn something new about a tool you have in your shed or maybe about a tool, an automotive fluid, a battery, or something else along those lines, I highly recommend giving Project Farm a watch. The tests are entertaining and who knows, maybe you might learn that a product isn’t as you expected.

(Photo credits: Project Farm/YouTube)

Support our mission of championing car culture by becoming an Official Autopian Member.

• I Drove A 2024 Diesel Ford F-250 And Now I Get Why People Daily Drive Huge Trucks

• Four Decades Ago, Nissan Made A Diesel Truck So Economical It Got Better MPG Than Almost Every Pickup Today

• How ‘Indirect Tire Pressure Monitoring Systems’ Work And Why We Should Celebrate Their Return

• Here’s How Dirt Cheap Tire Pressure Gauges Compare To Expensive Ones: Project Farm

• It’s Possible These Tires Weren’t Great: Cold Start

Please send tips about cool car things to tips@theautopian.com. You could even win a prize!