STP Fuel Injector Cleaner Review

Cars produced nowadays are subjected to stringent emissions regulations and thorough testing. Manufacturers have adapted to these laws by introducing direct injection almost entirely across the board and introducing technologies such as exhaust gas recirculation.

Direct injection achieves higher fuel economy and better performance, but this comes at a cost. In older style, port injected engines, the spray of fuel mixed with air that was directed just behind the valve would clean this area and prevent the formation of carbon deposits.

However, with direct injection, the fuel mixture no longer cleans engine surfaces, and combustion by-products can begin to group and materialize.

This build-up can be likened to the buildup of cholesterol and plaque in a person’s arteries, reducing performance and the effectiveness of the engine. Add to this the use of EGR systems, which direct waste gases that would otherwise have left the system via the exhaust, back into the engine.

This further adds to the build-up of soot and oily carbon deposits. With the extreme internal engine temperatures reached in the combustion process, these can become baked on and glaze over to a varnish-like coating.

To maintain engine power and health, it is now necessary to use fuel additives to combat the buildup of carbon.

Failure to do so can result in an early failure of the EGR valve that forms the basis of the emission control system and restricts airflow to the engine, choking the engine and increasing smoke and pollution from the exhaust as well as decreasing fuel economy.

Fuel injectors too can become coated, lowering their effectiveness and further compounding the whole problem.

There are some products on offer now to attack these builds up and help maintain a clean and high performing engine. STP Fuel Injector Cleaner is one such product.

Benefits of STP Fuel Injector Cleaner

  • Unclog carbon that builds up inside combustion chamber, piston heads, intake valves and EGR systems
  • Restores lost power & acceleration
  • Loosens waste deposits for burning
  • Improves fuel economy by saving fuel
  • Can reduce tailpipe smoke & emissions
  • Inhibits internal engine corrosions

STP Direct Injection Fuel Injector Cleaner is synthesized based upon a solvent called PEA. PEA has been chemically engineered to dissolves and soften accumulations of waste product deposits. Failing to do so can choke the engine of air, increasing fuel wastage, emissions, cause hard starts and power loss.

How often should I use a Fuel Injector Cleaner like STP?

With every tank fill up, that’s because every single combustion cycle is contributing to the creation of carbon deposits. Using a fuel additive will help prevent that. STP produces a specific Deep clean injector treatment if you have heavy deposits or have never used a fuel treatment product before.

How much fuel can STP Injector Cleaner Treat?

Up to 28 gallons of gasoline

Will STP Fuel Treatment void my warranty?

No, it will not void warranties and is compatible with modern cap-less fuel systems.

How well does STP Fuel Treatment work?

From all of the tests we’ve seen, it delivers about average performance. It is designed to be used a preventative measure, with each gas tank fill up and should counter low-quality fuels ashing up your engine.

There does appear to be fewer reviews of this product online when compared to the likes of Sea Foam, Gum Out, and others. That may be down to marketing, or it could be stocked in fewer auto parts stores, but reviews are quite positive.

Customers said that it made the engine response sharper and less sluggish. A number reported real-world fuel usage improvements. It does seem to work, but the formulation may not be quite as effective as some of its competitors.

Why should I purchase STP Fuel Treatment over another product?

STP offers a money back guarantee which not all manufacturers do. They are obviously convinced this product positively improves your engines performance and economy.

What is STP Fuel Injector Cleaner made of?

The exact chemical formula of a product like this is closely guarded as a trade secret. But the MSDS lists the following:

  • Hydrodesulfurized Kerosene – Restores sulfur levels in fuel to increase lubricity. This is the main constituent of STP Fuel Injector cleaner.
  • Naptha – Used as a solvent to aid evaporation and combustion
  • Xylene – Flammable solvent used in industry, likely as a filler liquid, increase cetane and octane levels
  • Trimethylbenzene – Another solvent that is billed as a lubricity enhancer
  • Ethylbenzene – For Anticoagulant / gelling of fuels in low temperatures
  • Toluene – A fuel octane booster


With the money back guarantee, this product stands out from the crowd. However, results seem to be fairly modest, and you’ll have to treat the tank several times to gain noticeable improvements. Worth a try if it’s all you can find at a local store or is available on offer.

Add Comment