Some On The Internet Claim Metal Pellets In Your Gas Tank Will Improve Performance. But Let’s Look At The Science

I found myself browsing automotive forums last week on my regular hunt for stories, and I happened upon a curious thing. Over on Corvette Forum, back in 2014 there was a guy working on a classic ’66 Corvette. He’d found a bunch of weird metal pellets in the gas tank and wondered what the heck they were doing in there. Ah! A mystery, and one I had to unravel. What I discovered was weirder, and in some ways sadder, than I could possibly have imagined.

The story at first seemed straightforward. Forum users stated these were lead pellets intended to be added to unleaded fuel to protect older engines. The oil companies started taking the lead out in the 1970s, so people put it back in in the form of pellets. The general idea was that this was an example of good old automotive snake oil. Simple enough, right?

That seemed to make sense, but I wanted the full story. As it turns out, these metal pellets are still on the market today, even for modern vehicles, and apparently they’re God’s own gift to motoring. We’re going to start by looking at their link to lead and leaded gas, then explore what’s actually going on with these mystery metal pellets turning up in gas tanks.

Why Did We Ever Use Lead In Gas?

Leaded gasoline didn’t just have elemental lead particles dissolved or floating around in it, or anything like that. Instead, it was dosed with a compound called tetraethyl lead, known as TEL for short. That compound has the chemical formula Pb(C2H5)4—a combination of lead with four ethyl groups, hence the name. It exists as a viscous transparent liquid at room temperature and is highly soluble in gasoline.

The compound was discovered to be an effective anti-knock agent to improve engine performance in 1921 by one Thomas Midgley Jr.— an American chemical engineer working at GM. At the high temperatures found in the engine, TEL quickly decomposes, splitting into lead and multiple combustible ethyl “radicals.” Radicals are highly reactive and can kick off or sustain a combustion reaction; indeed, many end up floating around in the fuel-air charge during the compression phase as heat and pressure ramps up.

However, lead and lead oxide in the combustion charge tends to react with any radicals in the fuel-air mix, stopping them from kicking off or sustaining early combustion (known as “knock”) before the proper ignition by the spark plug. It’s the lead that actually acts as the anti-knock agent — the ethyl groups simply serve as a way to mix the lead effectively with the fuel. TEL had a side benefit,  too—it helped cool intake valves and lead deposits stopped microwelds between valves and valve seats.

Those involved in the additive’s development were aware of its toxicity, but must have deemed the profit opportunities to outweigh the risks. As noted by The Conversation, despite the well-known hazards of lead and alarms raised by public health officials about TEL specifically, development went ahead. It was advertised under the simple name “ETHYL” to avoid the negative connotations around lead. Midgely suffered a serious case of lead poisoning due to his work, taking a long leave of absence to recover. Per this paper by a Radford University professor, seventeen workers would also die in the early efforts to produce industrial quantities of the additive in the 1920s. Meanwhile, Midgley and GM continued to promote the use of TEL in fuel until it became an effective industry standard. All the while, cars were spewing lead directly into the environment.

Phaseouts only seriously began once catalytic converters became necessary to meet air quality standards in the 1970s; lead in gasoline would poison the catalyst material, making it useless. It took until 2021 for the world to abandon leaded gasoline completely. That is, except for aviation—where 100LL “low lead” fuel continues to be used in piston-engined aircraft. A phaseout is targeted for 2030 at this stage.

For his pioneering work, Midgley has been referred to as a “one-man environmental disaster”—not only did he put lead in gasoline, but he also developed CFC refrigerants, which are remarkably effective at tearing holes in the ozone layer. Unlike leaded gasoline, though, the negative effects of CFCs weren’t well understood until decades after his death in 1944.

Lead Pellets To The Rescue! (Right?)

To a lot of people, “leaded gasoline” doesn’t mean gasoline with a special TEL compound in it. It just means gas with lead in it. Thus, if you wanted to run your car on the good old leaded gas, despite the phaseout, surely you could just put the lead back in yourself! That makes sense, right? And thus, these metal pellets are just bits of lead?

The thing is, this doesn’t actually work. If you drop chunks of lead in your gas tank, you’ve just got gasoline with a lump of lead in it. The lead doesn’t dissolve in the fuel in any way, it just sits there. It does precisely nothing to boost the fuel’s knock resistance or octane rating, and it does nothing to preserve the valves or valve seats, either. It just sits in the tank. This is why companies like DuPont spent great sums creating plants to make tetraethyllead, because that’s how you actually get the lead into the fuel.

There’s a perception in some sectors that old leaded gasoline is better, particularly for vehicles designed to run on the stuff. Sometimes that’s down to misty eyed nostalgia from those who grew up with elevated blood lead levels for some mysterious, unknowable reason. Sometimes it’s rooted in some fragments of fact. The truth is that early leaded fuels did have higher effective octane ratings, allowing engines to run at higher compression ratios without knock. The lead also offered a protective effect to valves and valve seats. Thus, simply switching to an unleaded petrol without considering the implications could cause problems.

However, these issues have since been solved. Modern unleaded gasoline is available in lovely high-octane grades that help avoid knock. There are also additives available to reduce valve seat wear in older engines. If your valves or valve seats wear out, you can replace them with hardened parts that don’t need any lead to reach their proper useful life.

In any case, this all seemed to line up — I figured the forum story was just about lead pellets showing up in old gas tanks because people wanted to put the lead back in. Only, then things got more complicated.

‘Fuel Catalysts’

I initially believed that the metal pellets from the Corvette forum were being sold as supplementary lead to add to fuel. However, thus far, I haven’t been able to find any period advertisements indicating that. That’s not to say they don’t exist—there certainly could be such a product. But, as alluded to in the Miller Oils paper above, it turns out these pellets may actually be made of something else. Does that mean they’re legit? I’m not convinced—but I’ve gone to great lengths to collate the evidence so you can assess for yourself.

In the case of the forum post I mentioned at the start of this article? Those appear to be Fitch Fuel Catalysts. They’re sold in two primary formats—the first being a set of metal pellets in a plastic housing. They’re intended to be dropped into a fuel tank of an older pre-1980 vehicle without an anti-siphon device in the filler neck. If you’ve got a newer vehicle, the company will sell you an in-line catalyst device instead for splicing into your fuel lines.

For context, the idea of a catalyst in chemistry is something that aids or supports a chemical reaction, without actually taking part of it. So, these devices are supposedly acting to help the fuel go under a chemical change, without being used up or absorbed into it.

Annoyingly, most “How It Works” videos or documents from these companies fail to explains anything at all.

Fitch’s website (fitchfuelcatalyst.com) will tell you that its device “reformulates gasoline and diesel resulting in a more complete burn and allowing you to extract more energy/gallon from your engine.” The product will apparently let you run a vehicle that needs premium gas on lower grade fuel, and that you’ll get more complete combustion, too. Oh, and more horsepower and torque. As a bonus, the catalysts supposedly “permanently” stabilize your fuel and protect against bacterial growth. The device is warranted for 250,000 miles, long enough to be a lifetime application for most vehicles. It’s good for everything from lawnmowers to motorcycles and automobiles, too.

There is a document on the Fitch website that explains in more detail what the catalyst does. It says the catalyst helps attach more oxygen molecules to the hydrocarbon molecules in the fuel, thus allowing it to burn better. What isn’t clear is where this oxygen comes from. For an in-tank catalyst, one could imagine the oxygen coming from some limited quantity of air in the tank. However, in the case of an inline device, there’s no obvious supply of extra oxygen to enter the fuel.

You can find these things all over the place. It appears even Summit Racing used to carry them at one point, though they’re now “not available.” But you’ll find them on sale all over the place on eBay, on Amazon, and beyond.

Sadly, though, the company is cagey about what they’re actually made of—not mentioning lead or any other material. Frustratingly, while a ton of other companies make very similar looking products, they’re all equally vague too. Not only do they not talk about composition, they don’t talk in any real detail about how these products actually work. They just allude to vague chemical changes in the fuel without specifying what those are. They all also tend to highlight that this occurs via catalytic action—with their material acting only as a catalyst to support reactions within the fuel, rather than being absorbed into it like an additive.

You can find plenty of these devices if you simply search for “fuel catalysts.” Many seem to be sold with reference to classic vehicles, again seemingly leaning on some kind of angle related to leaded gasoline.  You can get a particularly janky version off eBay that has a few metal pebbles wrapped up in a bit of steel mesh, presumably so they don’t get sucked into the tank’s fuel outlet and block it. This is often marketed as the “Formula Power Fuel Catalyst” citing that it was developed in 1941 by the Royal Air Force.

Indeed, as I researched further, I eventually found myself querying that tale. Supposedly, during Operation Benedict in World War II, British planes were struggling to operate on low-octane Russian fuel, if you believe Wikipedia. The lone citation for this is a random PDF on the “Broquet Fuel catalyst.” Would you believe it, Broquet is another brand selling these magic beans! According to the story, a special tin catalyst was able to spice up the Russian fuel to help boost the British fighters to their proper performance.

Other sellers seem to lean on varying retellings of this story. I found a defunct brand called Carbonflo which included a similar tale on its now-deceased website.

Did Anyone Do Science?

Indeed, there are a lot of commonalities between the sellers of these products. Most stack their websites with testimonials, and some even have example tests to prove their value. Fitch has a curious dyno test video from 2009 that suggests its product provides a hilariously minor boost to horsepower, well within the margins of error on a dyno, while also claiming a boost to economy. The company also cited chemist Steven Suib from the University of Connecticut.  Meanwhile, Carbonflo quoted one Professor G.E. Andrews, a combustion expert from the University of Leeds in the UK. Naturally, I have reached out to these individuals for their comment on these matters—given these companies are quoting them as experts in their fields.

Supposedly increases fuel efficiency. See description.
byu/Sadangler inMechanicAdvice

This Reddit post mentions spotting these devices at the University of Connecticut. I’m hoping chemist Steven Suib is able to get back to me with his comments on the matter.

Looking down this road led to one small hint of legitimacy. Dive into the research website of the Suib Group, and you’ll find a 2005 paper entitled “Effect of a metal alloy fuel catalyst on bacterial growth” with Steven Suib as one of the authors. It covers the case of a “fuel reformulation” catalyst made of tin, antimony, lead, and mercury, and its affect on bacterial growth in fuel. The paper directly mentions Advanced Power Systems International, Inc., a company apparently linked to Fitch. It suggests the alloy was able to reduce bacterial growth in fuel, but doesn’t touch on the other supposed benefits of the catalyst. Looking through Suib’s other publications, I was unable to find a paper that more directly covered the chemistry at play with these metal alloy pellets. Having reached out to Suib for comment, I’m dearly hoping to hear back, because it’s clear he was once investigating these in some sort of scientific capacity.

The U.S. Government Mentions These ‘Magical Beans’!

There’s also a curious mention of this technology by the US government itself. As cited by FTC, there is a vague mention of fuel catalyst technology in the 107th Congress 2nd Session House of Representatives Report. It was tabled by the Committee on Armed Services, and you can find it here on page 292 and 293. It seems to suggest these catalysts have some grand capabilities. The document states that the Marine Corps tested a system for diesel engines that improved fuel economy by 38.7 percent and reduced emissions by 44.8 percent. Wild numbers! Similarly, the Navy apparently saw “exhaust pollution” cut by 39 to 50 percent, and a 21 percent reduction in fuel consumption.

Those numbers are what we’d call insane. Imagine bolting on one component to an engine and improving your fuel economy by over 20%! “Given the magnitude of potential fuel savings and emissions reductions, the committee does not understand why the Department has not taken advantage of this technology,” reads the report. The Secretary of Defense is then urged to adopt the technology post haste.

So wait, did the US military miss a trick? Are they that stupid to ignore such epic savings? Well, let’s actually examine, here. I looked at the “More Capable Warfighting Through Reduced Fuel Burden” report, found on a US military server, and found no mention of fuel catalyst technology whatsoever. Furthermore, I was unable to find any record of such a test run by the Marine Corps. However, I did find an unverified PDF on a website called “voja.nl” that appears to allude to testing done by the Naval Facilities Engineering Service Center using an unidentified “RENTAR” fuel catalyst. Results were mixed in truck testing, with questionable sensor readings and many vehicles dropping out. Meanwhile, in a shipborne test, it apparently achieved negligible fuel economy increase and no noticeable improvements to carbon build up. In any case, the report doesn’t look quite right, and it’s hosted on the site of a company that sells fuel catalysts. I’ve contacted the Naval Facilities Engineering Service Center to comment on whether this report is legitimate.

Real talk? There doesn’t appear to be a genuine source for those exceptional performance figures in the Congress report. It appears somehow, a committee member may have ended up with misleading information with little basis in truth. After all, if those numbers were legit, the US military would be rushing to adopt the technology—and just about every other military on Earth would be, too. Fundamentally, I don’t believe there is science behind those wild figures quoted in the Committee’s report.

The University Of Aukland Dug Into This

Don’t give up hope, though, because I found something epic. A test regime run by engineers at the University of Auckland from 2002. They investigated a “Fuelstar” tin alloy additive to see if it had any notable performance benefit. This felt like striking a gold mine—just good old fashioned scientific testing done right. This isn’t some one-page outline of vague benefits or effects—it’s a full report on all the testing done and the results found! This is real science, people!

The author of the study ran a wide battery of tests with good scientific rigor, aiming to determine whether these pellets had any real value. They found no noticeable improvement from the use of the tin alloy pellets, either in benchtop test engines or in road tests of actual vehicles.

The full test is well worth reading and is full of scientific rigor beyond that of marketing materials and YouTube videos. I’ll just leave you with the study conclusions and some nice fuel economy graphs below. The pre-installation figures are in blue, the post-install figures are in pink—you’ll note the additive did nothing in this case.

A Curious Modern Example

It was late in the day when a particularly interesting example of this “technology” caught my eye. It was Mike Brewer, of Wheeler Dealers fame, and he was smiling in a video on fuel catalysts produced by a company called FTC. Published in December 2023, we see Mike sat down with a man called Simon, presumably from FTC, to talk about “miracle little pellets you put in your fuel tank.”

Simon actually gives us more information than the vast majority of fuel catalyst sellers. “All they are is tin and antimony,” says Simon. “Sometimes they’re made with a bit of bismuth in, sometimes a little bit of inorganic lead, but generally, they’re just tin and antimony.” If you’re unfamiliar, tin is a metal, while antimony is classified as a semi-metal element. Antimony is often mixed with tin or lead to make various useful alloys for soldering or bearing uses.

It’s here that FTC’s angle differs from the rest of the market. Simon talks down previous sellers of these products. He says that wild claims of boosted horsepower or fuel economy aren’t really legitimate. Instead, he says the primary role of these tin-antimony pellets is to help clean carbon deposits out of engines.

“These make cars run with completely clean engines, that’s what they do, and the fuel becomes the hero,” says Simon. “These will make that fuel clean your engine out.” He cites one example of a vehicle gaining a 1.4% fuel economy improvement due to the removal of carbon deposits which restored it to original factory performance specs, as well as a wild 28% reduction to carbon monoxide output. “Within an engine, there are deposits everywhere…These eliminate all deposits?” ” asks Mike Brewer. “All deposits, absolutely,” says Simon. “These will prevent deposits forming, but they’ll also remove them from engines where they’ve built up.”

There’s also a weird anecdote—the story of a Mini Cooper tested on a “rolling road” that got “116 brake [horsepower],” but that improved—”I think it was eight hundred thousand miles with the pellets in, she’s getting 119 brake [horsepower],” says Simon. Outside of the odd mileage claim—presumably a slip of the tongue to say she drove 800,000 miles—a three horsepower difference is well within margins of error across two dyno readings on two different days. Still, apparently the pellets cleaned out carbon deposits, improving performance and economy, and apparently the shifting of the automatic gearbox. Just magic. Oh, and the pellets? “These never wear out!” says Simon. “With these, you put ’em in, they work forever!”

Still, we don’t get any insight into the chemistry. “The fuel reacts against the surface of the pellet, the pellet never wears out,” says Simon. That’s about all we get. No information on how this makes fuel burn more completely or how it clears out carbon deposits at all. As one of the more active companies online right now in this space, I’ve reached out to FTC Direct for more information on their product.

A Professional Opinion

We wanted to get a professional to chime in on this topic. We reached out to Dr Andy Randolph, technical director of ECR engines. With 13 years experience at General Motors, and many more beyond that working on NASCAR engines, he knows a thing or two about internal combustion.

When we showed him the video above from FTC? He was not exactly impressed. Here’s what he had to say:

There were several comments in the video that caused it to lose all credibility.  Here are a few of them:

1. “Lead was put in fuel to mitigate the octane requirement increase due to deposit formation.”  Nope.  Lead was put in fuel to increase octane, period.  This octane increase allowed manufacturers to build engines with much higher compression ratio, hence increasing thermal efficiency (increased power output from burning a given volume of fuel).  It is true that carbon deposits were higher back then, but that is because engines were calibrated to run fuel rich (more fuel than oxygen) to increase power output.  We do the same in our race cars.  However, the advent of catalytic converters around the time lead was banned mandated engines run with the exact of ratio of fuel and oxygen to fully consume both.  This stoichiometry change also reduced carbon deposits because there was no longer excess carbon relative to the amount of oxygen.
2. “Premium fuel burns better than regular fuel and has more detergents to reduce carbon deposits.”  I am not aware of any fuel manufacture who uses an inferior detergent package in regular grades of gasoline.  If anything, premium fuel is more prone to deposits because the increased octane is achieved by increased quantities of carbon-dense aromatic hydrocarbons.  That said, the difference in deposit propensity is extremely small.
3. “Adding these pellets reduced emissions by 70% and fuel economy by 24%.”  Qualitative statements like that from extremely unscientific tests are red flags for me.  There were some other statements of more reasonable effects, but never an explanation of the mechanism.  I am a big believer in comprehending mechanisms to explain observations.  The mechanism of having a tin-antimony catalyst in the fuel tank that produces molecular changes in fuel composition to reduce deposit propensity totally escapes me.  The function of a catalyst is to encourage chemical reactions that would otherwise not occur.  It is quite easy to quantify the impact though species analysis with and without the pellets.  I cannot find any such analysis.

As you might expect from someone with a doctorate, Andy didn’t leave it there. “I did a quick Google search and found zero examples substantiating catalytic reactions in fuel from metal additives,” says Andy. “I did see several examples of metal additives in the combustion chamber, and of course metal additives are key to catalytic converter function, but I cannot find any studies quantifying catalytic effects sitting in a fuel tank.”

Beyond that, he points towards the value of common sense. “Another simple question to ask is ‘does it pass the sniff test?'” Andy asks. “The Clean Air Act states that vehicle manufacturers are responsible for ensuring their vehicles meet emissions standards throughout their useful life.” Indeed, used vehicles are tested on a regular basis to ensure manufacturers are compliant with EPA standards. “Are we to believe that auto manufacturers are unaware that a tin-antimony catalyst in their fuel tanks prevents carbon deposits and thereby reduces long-term emissions? ” says Andy. “Nope, doesn’t pass the sniff test!”

His ultimate verdict? “My two cents are to find better ways to waste your money than buying fuel tank pellets,” he says.

What Is The Truth?

I’ll be straight up. I’ve been asked to not get The Autopian sued, and I mostly try to stick to that. So I’m not goin to directly call out any particular product or company here. What I will say is that extraordinary claims always require extraordinary evidence. Where companies have made specific claims, or cited actual scientists, I’ve reached out to the scientists involved, and I look forward to their comment. I can’t say anything for certain, but on the surface—there are some big claims being made here without a lot of rock hard evidence.

At this point in time, it’s difficult to point to a straightforward chemical method by which these materials could improve fuel. Does tossing tin-antimony or lead pellets into fuel do anything? I’m not seeing any scientific literature that covers this sort of reaction. Maybe I’ve missed something, but it’s not obviously out there. If it does work, there should be a clear explanation out there of what chemical changes this metal makes to the fuel.

In any case, there’s a simple sanity check you can do with any product like this. If a few bucks worth of lead or tin or other “catalyst” pellets were enough to make a serious impact on performance, every automaker would be throwing these in the tank of every vehicle. Imagine if these did stop carbon deposits, for example—nobody would have to worry about cleaning intake ports on direct injection cars anymore! You could just throw some pellets in and be done with it. Automakers would prefer that to having to do more servicing and more warranty work.

Bennetts BikeSocial ran a test on a similar product called Tank Chip, made of tin, antimony, and lead. No consequential performance benefits were found. 

And yet, we don’t see a whole lot of metal pellets shipping in fuel tanks from major automakers. Similarly, if a tiny amount of catalyst could easily increase the octane rating of fuel at minimal cost, fuel companies would be doing so at the refinery level instead of messing about with other expensive octane-boosting additives. Particularly if the metal was barely or not-at-all consumed.

In any case, putting lead pellets in your gas tank will do nothing positive for performance. As for these fancy fuel catalyst pellets? Well, I’ll not say anything direct, but you’ll note I’m not spending my own money on these. Dollars for donuts, putting metal in your gas tank just makes your car heavier and will probably make a clanking sound during hard cornering. Save your money for maintenance and real performance upgrades, and avoid the heavy metal snake oil.

Image credits: FTC Direct via YouTube screenshot, FTC direct via website screenshot, Summit Racing, Fitch, Carbonflo, Penrite, Ethyl Corp, Jynto, CC0 license, Zodiac.nl, eBay, Amazon, Department of Mechanical Engineering – University of Auckland