Table of contents

  1. Fuel System Components
  2. Fuel Injectors/Carburettors
  3. Intake Valve
  4. Piston
  5. Combustion Chamber
  6. Which Fuel Additive Do I Need?

The fuel system is made up of the fuel tank, pump, filter and injectors or carburettor, and is responsible for delivering fuel to the engine as needed. Each component must perform flawlessly to achieve expected vehicle performance and reliability.

Fuel System Components

Over time, an engine’s performance can slowly diminish because of buildup, which clogs vital parts of the fuel system and causes reduced fuel efficiency and power.

Fuel Injectors/Carburettors

The fuel injector is the last stop for fuel in your engine before it goes "boom!" inside the combustion chamber. It is basically an electrically operated gate that opens just long enough to meter the perfect amount of fuel to run the engine.

Carburettors were the usual method of fuel delivery for most vehicles up until the late-1980s. Most carburettors are manual non-electric devices that are used for mixing vaporized fuel with air to produce a combustible or explosive mixture for internal combustion engines. Carburettors have been mostly supplanted by electronic fuel injection.

Intake Valve

The valve opens to allow the air/fuel mixture to be drawn into the combustion chamber. Deposits on the intake valves can restrict or change the flow of the air/fuel mixture into the combustion chamber. Fuel can stick to deposits on the intake valve and not enter the combustion chamber when needed. The right fuel additive can help reverse these effects and restore lost performance.


The piston travels up and down and converts the pressure from combustion into movement. Detergent additives that can help remove or reduce deposits have been shown to be effective in reducing or eliminating deposit-related drivability and performance loss.

Combustion Chamber

This is where burning of the air/fuel mixture happens. Deposits in the combustion chamber can affect heat transfer and air/fuel compression. Excess heat can cause premature ignition and knocking.

Some vehicles contain knock sensors that are used to determine engine knock or pre- or post-detonation. With these sensors, the computer will detune the engine to eliminate this symptom, which has an adverse effect on performance. Fuel system deposits will cause knocking, which is why it is so important to keep your fuel system clean.

Which Fuel Additive Do I Need?

Fuel additives vary by type and concentration. See below to find out which STP® products help prevent, remove or deep-clean deposits and learn more via our Fuel & Oil Additives guide.