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The Forgotten Maintenance Item

The Forgotten Maintenance Item

Two Guys Garage Podcast May 28, 2026 36 min
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About this episode

Fuel-system issues get overlooked, but they can strand cars and gradually make everything feel “old.” The hosts walk through how vapor locking, weak fuel delivery, and clogged carb jets or injectors reduce atomization and throw off the air-fuel ratio—often masked by modern fuel injection until it’s severe. They explain what they look for on injector bench tests, why low fuel concentrates sediment, and how lubricity and carbon deposits tie into drivability, emissions, and wear. They also discuss additive chemistry and dosing intervals.

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Technical Too Afraid to Ask
Term

fuel system

"When you think about the fuel system, you think about everything that the fuel system endures the environment. These, you know, these parts and pieces got to live in."

Your fuel system is how the car gets gas from the tank to the engine. It has parts that pump and deliver the fuel so the engine can run. If that system has a problem, the car can stall or leave you stranded.

Car

Dodge Charger

"I remember back in the days, bro, I used to have in town, it's to run around Winchester, Kentucky in the 71 Dodge Charger had a stroke 440."

The Dodge Charger is a classic muscle car. The host is talking about a 1971 Charger he had, and how fuel problems—especially heat-related ones—could leave it running poorly or stranded. It’s an example of how the fuel system can be the real culprit.

Term

vapor locking

"I always, I always fought like vapor locking, right? Some of the stupid things you fight as a kid when you're first exploring hot rods, you know, vapor locking, what's wrong with this, you know, and then a couple of little issues."

Vapor locking is when the gasoline in the fuel line gets so hot that it turns into gas vapor instead of staying liquid. Since vapor doesn’t feed the engine the same way, the car can run badly or stall. Letting it cool often fixes it temporarily.

Term

fuel delivery

"But, you know, fuel and fuel delivery. I always, I always fought like vapor locking, right? ... and then a couple of little issues."

Fuel delivery is how well the car gets gas to the engine when you need it. If the car can’t deliver enough fuel (or delivers it inconsistently), it can run rough or die. It’s often caused by problems in the pump, lines, or related parts.

Term

electronic fuel pump

"and then a couple of little issues. That's how I went through, you know, electronic fuel pump, then you fight, you know, getting the fuel, you know, delivered right."

An electronic fuel pump is the electric part that pushes gas from the tank to the engine. It helps keep the right fuel pressure so the engine can run smoothly. If it starts failing, the car may hesitate, stall, or not start.

Term

supercharged

"obviously as fuel injection progresses, we went through the years, supercharged stuff, boost, all that technology is added to it with fuel systems."

A supercharger forces extra air into the engine. When you add more air, the engine also needs more fuel to run correctly. If the fuel system can’t supply enough, the car can feel weak or run into trouble.

Term

boost

"we went through the years, supercharged stuff, boost, all that technology is added to it with fuel systems."

Boost is extra pressure that a supercharger or turbo adds to push more air into the engine. More air usually means you need more fuel too. If the fuel system can’t keep up, the engine won’t run right.

Term

jets clogged

"a lot more prevalent issues. Like you said, whether it's, you know, your little seat stock or your jets clogged or whatever, right?"

Jets are tiny fuel passages inside a carburetor that control how much fuel the engine gets. If they get clogged, the engine may not get the right amount of fuel.

Term

sludge buildups

"bad fuel, dirt in your fuel, you name it, right? Sludge buildups, you know, the, the waxy stuff."

Sludge buildup is gunk that forms inside the fuel system over time. It can clog small passages and make the fuel delivery less accurate.

Term

O-rings

"remember the Holley's that had that little shatty, had the little O-rings when you build it and they would constantly leak, you know, and, and, you know, how the,"

O-rings are rubber sealing rings used to prevent fuel leaks at connections. If they harden or fail, they can leak fuel, causing drivability issues and creating a fire risk.

Brand

Holley's

"feel, remember the, remember the Holley's that had that little shatty, had the little O-rings when you build it and they would constantly leak, you know, and, and, you know, how the,"

Holley is a company that makes carburetors and other fuel parts. The hosts are saying some older Holley carb setups had a reputation for leaking or wearing out seals over time.

Term

diaphragms

"and, and, you know, how the, all the diaphragms on the power bars would get all hard, you know, and plungers would get really hard on the carburetor."

A diaphragm is a flexible rubber/plastic membrane inside the carburetor that helps control fuel flow. If it gets stiff or worn out, the carb can’t regulate fuel properly.

Term

carburetor

"How many times have you rebuilt a carburetor? Like, why would you need to rebuild a carburetor? It doesn't necessarily break. It just stuff gets clogged in there and build up and junk in and you,"

A carburetor is an older way of mixing fuel and air for the engine. It has tiny openings that can get clogged, so dirty fuel can cause problems.

Term

fuel injection

"And, you I think what's happened with fuel injection is such leap and bound improvement. Absolutely. That it's really kind of hidden a lot of sins."

Fuel injection is how modern cars put fuel into the engine. Instead of a carburetor mixing fuel, small nozzles (injectors) spray fuel in a controlled way so the engine gets the right mixture.

Term

spray patterns

"You can physically put it on your bench and you can see the injectors like completely uneven and the spray patterns and all that stuff and everything"

Fuel injectors are supposed to spray fuel in a consistent shape. When they get dirty, the spray can become uneven, and the engine may not burn fuel as well.

Term

air fuel control

"really good atomization, great air fuel control, all that stuff just slowly goes away and, and you almost"

Air-fuel control is how the engine keeps the right balance between air and fuel. If the fuel system gets dirty, that balance can go off and the engine won’t run as smoothly.

Term

air fuel ratio

"If a good cleaning and everything comes out, like fine mist and atomized and air fuel ratio, your car will run probably a lot more like it was new again."

Air-fuel ratio is the balance of air and gas your engine uses to burn. If that balance is off, the car can feel weak and can also use more fuel and pollute more.

Term

atomized

"If a good cleaning and everything comes out, like fine mist and atomized and air fuel ratio, your car will run probably a lot more like it was new again."

Atomized fuel is fuel sprayed into a fine mist. A good mist mixes with air better, so the engine burns it more cleanly and efficiently.

Term

degradation

"Yeah. You find that to be true, Kyle, that it happens so gradually that people just, they become unaware of the degradation and their performance and the loss of, you know, just performance and how that car should feel and should drive."

In this context, degradation means gradual loss of fuel-system effectiveness over time—like injectors becoming less consistent or filters restricting flow. Because it happens slowly, drivers often don’t notice until performance and economy drop noticeably.

Term

fuel injectors

"I decided to get a fuel injection like machine, so I could clean fuel injectors and I could run certain tests on them... If it's coming out the injectors bad, imagine what the rest of the fuel systems looking like."

Fuel injectors are like precision spray nozzles for gasoline. If they get dirty or damaged, they don’t spray the fuel correctly, and the car can run rough or feel weak.

Term

atomization

"there's been so many cars that have just faulty fuel injectors, where you got bad atomization, where there's, you know, plunger issues... And you can see droplets instead of atomization"

Atomization is how finely the injector mists the gasoline. If it makes big droplets instead of a mist, the engine can’t burn it as well.

Term

plunger issues

"where you got bad atomization, where there's, you know, plunger issues, the screens are messed up, the actual valve body, you know, is so gunked up."

The injector has internal moving parts that control how fuel flows. If those parts don’t move right, the injector can spray incorrectly and cause running problems.

Term

valve body

"the screens are messed up, the actual valve body, you know, is so gunked up. And you can see droplets instead of atomization"

The valve body is part of the injector that helps control fuel flow inside. If it gets clogged with deposits, the injector can’t work correctly.

Term

bench test

"the end result, you'll see it on your bench test there on the injectors. If it's coming out the injectors bad, imagine what the rest of the fuel systems looking like."

A bench test means testing the injector on a stand instead of in the car. It helps show whether the injector is spraying and flowing correctly.

Term

carbon deposits

"And the biggest problem we generally see are carbon deposits, the carbon deposits that are left over, they tend to build up in the system over time."

Carbon deposits are gunk that builds up inside the fuel/engine system. If they get into the injector, it can spray poorly and make the car run worse.

Term

piston

"especially right at the piston where the injector level is, they want that pure atomization, they want a direct hit on that sweet spot of the piston"

The piston is the engine’s moving part inside the cylinder. The idea here is that the fuel spray has to hit the right spot on the piston to burn efficiently.

Term

air fuel mix

"So they're adjusting all the timing, [557.7s] the air fuel on the fly. And imagine that computer seeing the system run a little off,"

Engines need the right balance of air and gasoline to burn efficiently. Too much fuel or too little fuel can cause rough running and more soot/carbon buildup.

Term

O2

"It only has a few sensors like what's going down stream and the O2, right? How how long did I turn the injector on for?"

The O2 sensor checks the exhaust to see if the engine is burning too much fuel or not enough. The car uses that info to adjust the fuel so the engine runs correctly.

Term

injector on for

"It only has a few sensors like what's going down stream and the O2, right? How how long did I turn the injector on for? Really simple type stuff."

The computer controls how long the injector stays open. If the injector is dirty, that same “open time” can still end up delivering the wrong amount of fuel.

Part

bucket screen

"Hey, you know what are the parts when I take fuel injectors apart? They have this little kind of a [650.7s] bucket screen in there. And when you pull this thing out, it's amazing"

That “screen” is like a tiny filter inside the injector. If it gets clogged, the injector can’t spray fuel properly, and the engine may burn fuel less cleanly.

Term

ultrasonic

"They have this little kind of a bucket screen in there. And when you pull this thing out, it's amazing to put, I got a ultrasonic [656.8s] tray that that that you put this cleaner in and you clean injectors and a few other components"

Ultrasonic cleaning uses vibrations in a cleaning fluid to shake loose dirt from tiny parts. It’s commonly used to clean injector screens and restore better spray.

Term

injector issue

"We'll put a load on it won't open it and you'll see some of them drip through because it it can't seal up correct. You know, all these issues going on with modern injectors."

A fuel injector is a valve that sprays fuel into the engine. If it doesn’t seal right, fuel can leak or dribble instead of spraying correctly, which can hurt how the car runs.

Term

sediment

"And they got some old fuel with a rusted tank. And a lot of that sediment that you see in these injectors is actually coming from the bottom of the fuel tanks at the fuel pump itself."

Sediment is dirt or particles that settle at the bottom of a fuel tank. If it gets into your fuel system, it can clog or damage fuel system components.

Term

detergents

"We know that these fuel jobbers work in a world of fractions of pennies. So they just don't put as much detergents as needed in there."

Detergents in gasoline are like cleaning agents. They help stop gunk from building up in the fuel system and on injector parts.

Term

stabilizers

"They just don't put as much detergents as needed in there. They don't put as much stabilizers in there, especially for fuel has been sitting around."

Stabilizers help gasoline last longer without going bad. If fuel sits too long without stabilizers, it can form problems that affect the fuel system.

Term

quarter tank

"What about not running your car so, so empty, you know, running your car like when it gets down to quarter tank... don't let it get down to that bottom gallon or two."

When your tank is very low, you’re more likely to suck up dirt that has settled at the bottom. Refilling earlier helps reduce the chance of that contamination reaching the engine.

Term

direct injection

"Now, Kyle, you mentioned carbon deposits. Do you see that on the PFI side or mostly on the direct injection side? Because the direct injection, you know, tip is sitting in that combustion chamber in the heat."

Direct injection sprays fuel straight into the engine’s burning chamber. Since the injector tip is in the hot area, it can get dirty with carbon deposits, so keeping the fuel system healthy matters.

Term

PFI

"Now, Kyle, you mentioned carbon deposits. Do you see that on the PFI side or mostly on the direct injection side? ... Yeah, on like port inject stuff in the intake valves, you'll see it."

PFI means the fuel is sprayed into the intake area before it reaches the combustion chamber. Even though it’s not “direct,” deposits can still build up—like on the intake valves.

Term

30,000 PSI

"And so there's, there's, you got to almost, you know, count on a better fuel, tough to clean on that side, of course, but it is an ongoing problem. And the tire of these systems are coming, they're coming under more pressure too, kind of like as we know on the diesel side, you know, those systems can be 30,000 PSI."

PSI is a measure of pressure. The point here is that diesel fuel systems can run at extremely high pressure, so tiny problems can become big problems because the system has to be very precise.

Term

fuel economy standards

"And with all the fuel economy standards that they're bringing in now, these are getting really advanced on these fuel injections, but they also means it's more important."

Fuel economy standards are rules that require cars to use less fuel. To meet them, manufacturers use more advanced fuel injection, so the fuel system has to stay in good shape.

Concept

maintenance for the longevity of the vehicle

"The gasoline world needs to take note of what's going on in these new injected systems and know that it's a, it needs to be a point of maintenance for the longevity of the vehicle."

They’re saying fuel-system care is important for keeping the car running well for years. With modern injection systems, dirt and deposits can build up faster, so it’s worth treating fuel maintenance as a real upkeep item.

Term

carbon cleanup

"There's a lot of products out there that do carbon cleanup. There's a lot of lubricant products out there."

Carbon cleanup is about removing sticky black buildup that forms as fuel burns. Over time it can hurt how the engine runs, so people use additives or treatments to reduce it.

Concept

preventative about it, be on the front end

"So be preventative about it, be on the front end about it, put good fuel in, clean your system regularly like you do the rest of your system."

This is the idea of preventive maintenance for the fuel system: cleaning and maintaining it early to avoid problems that build slowly. Once deposits and wear issues progress, repairs tend to be more difficult and costly than routine upkeep.

Term

E85

"the OEs kind of marched down that whole E85 route, you know, whether it was flex fuel and even down in the E15, there was a whole lot of challenges."

E85 is a type of fuel made from mostly ethanol mixed with some gasoline. Because it’s different from regular gas, it can affect how well the fuel protects engine parts from wear.

Term

flex fuel

"you know, whether it was flex fuel and even down in the E15, there was a whole lot of challenges."

Flex fuel refers to vehicles designed to run on more than one fuel blend, typically including ethanol blends. These systems often require calibration and component materials that can tolerate ethanol’s different effects on wear and corrosion.

Term

E15

"whether it was flex fuel and even down in the E15, there was a whole lot of challenges."

E15 is regular gasoline with a small amount of ethanol mixed in. It can still change how the fuel behaves in the engine compared to pure gasoline.

Term

lubricity

"some of the other hidden challenges in lubricity. E85 doesn't naturally have the same lubricity as gasoline, which you think doesn't have much, which it doesn't, but it shows you that it's doing something"

Lubricity just means how well the fuel can “lubricate” moving parts inside the engine. If the fuel doesn’t lubricate well enough, parts can wear out faster—so some engines need tougher materials when using certain fuels.

Term

valve seats

"So they had to upgrade things like valve seats, right? To harder valve seats, harder, uh, harder valves."

Valve seats are the contact surfaces in the engine head where the valves close and seal. If the fuel doesn’t lubricate well, that contact can wear out sooner, so some engines use tougher seat material.

Term

upper cylinder lubricant

"And another great part of it about that, lubricity is that the lubricity can also bring some efficiency and power as well as an upper cylinder lubricant."

This means lubrication that helps protect the parts near the top of the engine where they move a lot and see high heat. The claim here is that better lubricity can reduce wear and help the engine run more efficiently.

Term

C-tane

"on the diesel side, as we raise C-tane, it wants to drop lubricity, you bring lubricity up, but it wants to drop the C-tane."

Cetane is a diesel fuel property that affects how easily the fuel ignites in the engine. If cetane drops, the engine can run less smoothly. They’re saying their additive raises lubricity but tries not to lower cetane.

Term

carbon buildup

"but all this carbon buildup, all these, you know, components are failing because of this buildup of all this junk and gunk."

Carbon buildup is gunk that forms inside the engine over time. It can make the engine run less smoothly and can contribute to parts wearing out. The hosts say this deposit problem is a major cause of failures.

Term

polyetheramine

"here's your word for the day, polyetheramine, which is PEA. ...it's the best carbon cleaner out there."

Polyetheramine (PEA) is a cleaning chemical added to gasoline. Its job is to break up and remove carbon deposits that build up in the engine. The hosts say it’s one of the strongest cleaners they use on the gasoline side.

Term

EPA

"The main difference that we do is that we max out literally where the EPA can stop us on how much of this PEA we put into the product."

EPA is a U.S. government agency that sets rules for things like fuel additives. The hosts are saying there’s a legal limit on how much of the cleaning chemical they can put in. Their product uses the maximum allowed amount.

Term

fuel tank

"there's a lot of those products that you could pour in the fuel tank that do a good job of cleaning, but they're the type of products that you have to dump right away."

The fuel tank is the container that holds your gas or diesel before the engine uses it. The hosts are warning that some additives can clean aggressively and may affect how well the fuel lubricates parts during that process. Their product is meant to clean while keeping lubrication up.

Term

PEA

"dose of PEA. Cause I think the standard, you know, you talked about in gas stations, right? The, ... they're running on pennies for margins."

PEA is a chemical added to gasoline that helps keep the fuel system clean. Cleaner fuel flow can help the engine run better because it reduces gunk that can build up over time.

Term

gasoline cleaning market

"as we entered the gasoline market being known as a diesel focused company, um, when we entered this gasoline cleaning market ..."

The “gasoline cleaning market” refers to the aftermarket products sold to improve fuel-system cleanliness—typically by using detergent additives that reduce deposits. This segment frames it as a competitive space where different formulations and dosing schedules are marketed to consumers.

Term

LX4

"So we maxed out the amount of PEA that you can put in there while also using our exclusive LX4 to lubricate at the same time."

LX4 is a product ingredient they claim helps lubricate the fuel system. They’re saying it’s used together with their main cleaner so the treatment both cleans and protects.

Concept

deep cleaning

"You need it every 3000 miles or, or so we're putting so much in that we know that we can clean that system fully and get you down the road for another 10,000 miles before you need to do another deep cleaning."

“Deep cleaning” here means a stronger fuel-system treatment meant to scrub out buildup. They’re claiming it works for a long stretch (about 10,000 miles) before you need another dose.

Term

fuel additive game

"I hope you bring the same standard, which is severe, you know, up a level up from, from where it's at right now in the fuel additive game."

They’re talking about the business of products you pour into your gas or diesel. Some are legit, but others are mostly marketing, and the hosts are saying the bar should be higher.

Concept

placebo

"When we first launched this product, we did a thousand car study, uh, with a placebo, uh, our product and then another leading manufacturers product. And it was a blind study."

A placebo is a fake version of the product used in testing. In a blind study, people don’t know whether they got the real thing or the fake one, so results are less likely to be influenced by expectations.

Term

fuel mileage

"had an increase in fuel mileage of 7.9%. Now let's dive into those numbers a little bit."

They’re talking about how efficiently the car uses fuel—basically how many miles you can drive per gallon. It’s the main number they’re claiming the additive improves.

Term

emissions

"So you're going to be riding the top edge from emissions and you name it, right? Through the life [1650.3s] of your car versus, because even like you say,"

Emissions are the exhaust pollutants a car makes. Keeping the engine clean can help it burn fuel more properly so it stays within emissions goals.

Car

Ford Mustang

"...ere in the studio doing a car. I believe it was a Mustang because it sounds like something Mustang would do..."

The Ford Mustang is a sports car made by Ford, usually as a coupe or convertible. It’s designed to feel fast and exciting, and it’s been around for many years. People talk about it a lot because it’s a recognizable, performance-oriented car.

Term

power steering

"But when you, when you had, when you had the power steering all the way over, it was on an older box, it was an older car because it had a power steering pull and it [1730.1s] was"

Power steering helps you turn the wheel with less effort. In the story, they mention turning it fully to show what was happening during the test.

Term

rack to rack

"pump and just said, okay, run it rack to rack side to side. And you did that and it was totally gone."

“Rack to rack” means turning the steering wheel all the way from one side to the other. That forces the power steering system to move fluid through the steering parts. They use it as a simple way to see if the problem goes away.

Concept

money back guarantee

"we're the only one that offers a money back guarantee on every one [1782.9s] of our products. No questions asked."

A money-back guarantee means if you try the product and don’t like it, you can get your money back. They’re using it to make it easier for people to take a chance on a product they might be skeptical about. It’s about trust and risk reduction for the buyer.

Term

FR three

"and if you're, if you don't believe what Willie just said, I challenge you to go throw a little [1795.6s] bit of sticks, eliminate your FR three and your power steering pump and see how much it moves."

“FR three” sounds like a specific fuel additive or product the speaker is talking about. They’re basically saying: remove that stuff and see what happens. The transcript doesn’t make the exact name totally clear, but it’s part of their “prove it” challenge.

Brand

gasoline extreme

"if anybody wants to try this product, the gasoline extreme [1837.8s] is available on our website."

“Gasoline Extreme” is the name of the fuel additive they’re selling. They’re saying it helps with problems related to gasoline, and they back it with a money-back guarantee. It’s the product they want you to try.

Brand

hotshotsecret.com

"the gasoline extreme [1837.8s] is available on our website. You can go to hotshotsecret.com and order it."

Hot Shot’s Secret is the brand selling the gasoline additive they’re talking about. They say you can order it from their website and use a tool to find nearby stores that carry it. It’s basically where you’d buy the product they recommend.

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