How to Clean Fuel Injectors: Gas and Diesel

Using proven AMSOIL fuel additives can save you money on expensive maintenance.

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AMSOIL Diesel Injector Clean Fuel AdditiveAMSOIL Diesel Injector Clean Fuel AdditiveAMSOIL Diesel Fuel AdditivesAMSOIL Diesel Fuel AdditivesAMSOIL P.i. Performance Improver Gasoline AdditiveAMSOIL P.i.® Performance Improver Gasoline Additive
Brad Nelson
by Brad Nelson
May 15, 2025

Your engine’s fuel injectors deliver fuel into the combustion chamber in synch with the motion of the pistons. But, the diameter of an injector orifice is tiny, even smaller than the diameter of human hair. Therefore, it’s common for carbonaceous deposits on injectors to impede fuel flow and starve your engine of fuel, dramatically reducing performance. The good news, your injectors can be cleaned to restore horsepower and torque.

So, you want to know how to clean your fuel injectors?

AMSOIL Tech Tips on Motorhead Garage with host John Gardner and AMSOIL product expert Len Groom: How to Do a Fuel Injector Flow Test
Video transcript: How to Do a Fuel Injector Flow Test

Featuring John Gardner, ASE Master Certified technician, automotive technology instructor and host of Motorhead Garage, with AMSOIL Director of Product Marketing Len Groom (author profile).

John Gardner: Well, here are four injectors with four different spray patterns. This one’s dripping, that one’s spraying a stream, that one’s offset, and that one looks pretty good. I don’t know which one you want, but I know which one I’d pick. Welcome to this AMSOIL Tech Tip. It’s all about injectors and how they flow, and I’ve got a cool demo here. Let me fire this thing up. This is going to run the injector system: you’ve got inputs, a computer and outputs running these injectors.

Len, I can feel these injectors. I know they’re pulsing; I know the computer’s pulsing them. But I don’t have a clear intake on a car, so I really can’t see what’s going through them. I think a flow test is in order.

Len Groom: I agree.

John Gardner: To do that, we’ve got a pressure gauge hooked up, and I’ve got the fuel pressure jacked up. What I’m going to do is unplug this first one. When I unplug it, you’ve got a computer simulator over there that’s going to open and close this injector. Go ahead and hit it. Here we go: about 34.

Len Groom: 34.

John Gardner: Yeah, and you just compare that to all the injectors. We’ll bring the fuel pressure back up and try another one. About 34. It’s flowing the same. Now, if this one wasn’t flowing at all, or was flowing less, you’d know you’ve got a restriction. If we’ve got a clogged injector, how can AMSOIL help us?

Len Groom: AMSOIL fuel injector cleaners, specifically our AMSOIL P.i. Performance Improver and our AMSOIL Upper Cylinder Lubricant. Those are the two key products for a gasoline system. You want to keep the injectors clean, and you want to make sure the entire system is free of deposits. That’s what you do with P.i., every 4,000 miles. Upper Cylinder Lubricant goes in every tank, so you’re treating your fuel all the time. The key is a clean system, clean injectors and a good spray pattern.

John Gardner: Speaking of spray patterns, I think we learned we want ours to look like that, and that’s what yours is going to look like when you use AMSOIL. Check out all their fuel-injection products and so much more at amsoil.com.

Pay the pros

One method is to take your vehicle to a mechanic and have them clean your injectors for you. However, as you might guess, this is not the cheapest approach, and it comes with the hassle of scheduling service and living without your vehicle while it’s at the shop.

Do it yourself

You could take on the project yourself. You can easily find instructions online on how to remove fuel injectors from the engine, clean them and reinstall them. The process can be done with the right tools and knowledge, but there is an easier way.

Ford F-350 Super Duty diesel pickup driving on a mountain road

Use a fuel additive

Using the right fuel additive to clean fuel injectors is a simple approach that’s also inexpensive and just as effective. However, as this post explains, this technique requires a fuel additive with enough strength to get the job done.

AMSOIL P.i.® Performance Improver

AMSOIL P.i. Performance Improver gasoline additive contains concentrated detergents that aggressively clean stubborn, power-robbing deposits from injectors, valves and the combustion chamber. It’s effective in port and direct-injection systems and cleans the entire fuel system in one tank.

AMSOIL P.i. restores GDI fuel injectors up to a 100% flow rate¹ and restores up to 14% horsepower.² P.i. also fights intake valve and combustion chamber deposits to help restore power, control knock and reduce the need for higher-octane fuels. Use AMSOIL P.i. every 4,000 miles to thoroughly clean the injectors, valves and combustion chamber.

AMSOIL P.i. increases horsepower.

AMSOIL Upper Cylinder Lubricant

Your engine’s top-end is sparsely lubricated and prone to the development of deposits and corrosion, an issue compounded by ethanol in fuel. While P.i. Performance Improver is designed to attack and remove stubborn deposits, Upper Cylinder Lubricant helps preserve injector and combustion-chamber cleanliness between P.i. treatments. Use AMSOIL Upper Cylinder Lubricant in every tank of fuel to help maintain peak performance.

AMSOIL Upper Cylinder Lubricant also delivers 18% more lubricity than Lucas* and 20% more than Sea Foam* for better retention of horsepower and fuel economy.³

Graph shows that AMSOIL Upper Cylinder Lubricant delivers 18% more lubricity than Lucas* and 20% more than Sea Foam* for better retention of horsepower and fuel economy.
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AMSOIL Diesel Injector Clean

AMSOIL Diesel Injector Clean will take care of your dirty diesel engines injectors. Its concentrated formula uses unique chemistry to target and eliminate carbonaceous deposits and help maximize power. Use AMSOIL Diesel Injector Clean in every tank of fuel to help maintain maximum performance.

AMSOIL Diesel Injector Clean

AMSOIL Diesel 4-IN-1

AMSOIL Diesel 4-IN-1 provides better cold flow, increases cetane, fights fuel-system corrosion and cleans injectors to help restore lost power and torque and reduce smoke and emissions. Use it regularly to increase diesel fuel lubricity for improved wear protection.4 Maintain your diesel engine by adding AMSOIL Diesel 4-IN-1 to each tank to help clean dirty injectors and provide exceptional all-season protection and performance.

Bar chart showing diesel fuel lubricity improvement with AMSOIL Diesel 4-in-1 in fuel samples from several states
Bottle of AMSOIL Diesel 4-in-1 fuel additive

How to clean fuel injectors

You don’t have to take your vehicle to a mechanic to fix clogged injectors or live with the loss of horsepower and performance. High-quality AMSOIL fuel additives can help clean clogged fuel injectors and keep them clean with minimal cost and effort.

1ASTM D5598(M) – 2013 Buick Regal test vehicle.

2Based on third-party testing in a 2016 Chevrolet* Silverado* 1500, 5.3L V-8 GDI with 100,616 miles, using one tank treated with AMSOIL P.i. Actual results may vary.

3Based on independent testing of AMSOIL Upper Cylinder Lubricant, Lucas Upper Cylinder Lubricant and Sea Foam Motor Treatment obtained on 02/13/2019 using the ASTM D6079 modified for use with gasoline.

4Fuels tested in 2017.

This article is part of our Fuel and Fuel Additives guide. See every article in the guide.

by Brad Nelson

Brad Nelson is an AMSOIL Technical Writer II who develops content about lubricant technology, product performance and vehicle maintenance. He works with engineers and product specialists to translate testing, application requirements and approved performance claims into clear customer guidance. Nelson’s work includes AMSOIL Blog articles, AMSOIL Magazine features and technical explanations concerning motor oils, gear lubricants, vehicle systems and maintenance practices.

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AMSOIL Diesel Injector Clean Fuel AdditiveAMSOIL Diesel Injector Clean Fuel AdditiveAMSOIL Diesel Fuel AdditivesAMSOIL Diesel Fuel AdditivesAMSOIL P.i. Performance Improver Gasoline AdditiveAMSOIL P.i.® Performance Improver Gasoline Additive

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