Do You Put Fuel Injector Cleaner in Before or After Gas?

Do You Put Fuel Injector Cleaner in Before or After Gas

If you are using a much older car, there is a need to use fuel injector cleaner because there will be a buildup of carbon that may eventually clog the fuel injector.

In adding fuel injector cleaner, do you put fuel injector cleaner in before or after gas? It is better to put injector cleaner in before gas, preferably with the gas tank half-filled or nearly empty.  

What is an Injector Cleaner?

Injector cleaners are liquid (solvents) used in dissolving and cleaning out buildups in the injection system. Although there are usually fuel filters in place to collect particles and debris, some still find their way into the fuel injection system and over time cause a buildup of deposits.

They are usually made up of polyisobutylene amine, polyether amine, and polyisobutylene. These ingredients are an important part of an effective injector cleaner.

Injector cleaners are poured directly into the gas tank and it immediately starts working once the car is driven, cleaning starts when combustion takes place.

Apart from dissolving solids in the injection system, the injector cleaner also prevents its buildup if used regularly.

Do you Put Fuel Injector Cleaner in Before or After Gas?

For fuel injector cleaner to be effective, you should add it in before gas. Adding before gas allows the cleaner to dilute and mix well with the gas once you fill-up.

You are at no risk of harming the engine if you add cleaner after gas but if you want the maximum result, add before gas, and when the tank is half empty or nearly empty.

Do You Have to Put Fuel Injector Cleaner in an Empty Tank?

You do not have to put fuel injector cleaner in an empty tank, however, if you want to get the desired result you should definitely add fuel injector cleaner in an empty or close to an empty tank.

It is usually advisable to put injector cleaner in an empty, near-empty, or half-filled but not full gas tank. This is so the ratio of cleaner to fuel will be balanced.

Although advisable to put a fuel injector cleaner in a near-empty tank, you should resist the urge to put it in a completely empty tank.

Injector cleaners contain some fairly concentrated components and also require an amount of fuel to be diluted.

If the cleaner is added directly inside the gas tank with no fuel inside, the detergent will likely damage the engine because it is not diluted.

Adding to an empty tank will damage the engine, adding to a full tank will render the cleaner ineffective, it is much better to add to a nearly empty or half-filled gas tank.

How Long Does Fuel Injector Cleaner Take to Work?

The length of time it takes a fuel injector cleaner to begin work hinges on some factors but all things being equal you should start seeing results within 100-300 miles of adding the cleaner.

Although it may take some time for one to see a noticeable improvement in the vehicle’s performance after adding injector cleaner, the cleaner starts work immediately.

Some of the factors that will affect and influence the time it takes an injector cleaner to work will be discussed below.

The Type of Fuel Injector Cleaner Used

One major determinant of when the injector cleaner starts working is the type of cleaner used. There are varying kinds of injector cleaner out there made up of different components.

Its ability to quickly start work in dissolving deposits depends on how the main components are combined. These main components are; Polyisobutylene amine, Polyether amine, and Polyisobutylene.

Polyisobutylene amine is the mildest of all the chemicals and works best at cleaning fuel lines, polyether amine is suitable for cleaning injector systems with large buildups while polyisobutylene is used in removing buildups in the combustion chambers.

Vehicle Fuel System Condition

Relatively old engines will have a lot of buildups which will take a longer time to dissolve, new engines on the other hand won’t have so many buildups and therefore will be cleaned out in no time.

Will Fuel Injector Cleaner Fix a Misfire?

Yes, a fuel injector cleaner can fix a misfire. An engine misfiring can be a result of various issues with some parts of the engine as well as carbon tracking. The fuel injector may be clogged with carbon building thereby resulting in a misfire.

When an engine misfires, it will idle roughly, stumble, and may even in lose speed. It doesn’t happen for a long period but definitely a sign that something should be fixed.

The use of fuel injector cleaner in the injector system helps to dissolve and clean out the carbon buildup thereby fixing the problem of misfiring.

Can Fuel Injector Cleaner Damage Fuel Pump?

A fuel injector cleaner can damage the fuel pump, however, this doesn’t happen all the time. For an injector cleaner to damage a fuel pump, the cleaner used wasn’t compatible with the car’s system.

If an injector cleaner not compatible with the car’s system is used, it will do a poor job of dissolving the buildups i.e. the buildups won’t dissolve completely and the fuel injector will still remain clogged.

A clogged fuel injector will eventually damage the fuel pump.

One way to avoid damage to the fuel pump is by ensuring that only recommended fuel injector cleaner is used in the tank. If you realize the mistake after the cleaner has been added you will need to drain out the internal system

Does Fuel Injector Cleaner Clean Spark Plugs?

A fuel injector cleaner may be able to clean spark plugs to an extent. Spark plugs are an important part of an engine’s combustion process without which combustion will not happen.

With use over time, there may be a need to clean spark plugs although cleaning is usually temporary until they can be replaced.

To effectively clean spark plugs with fuel injector cleaner, the oil mustn’t be contaminated. Once the oil is contaminated, there is nothing much that can be done.

In cleaning spark plugs with fuel injector cleaner, remove the spark plug then pour the injector cleaner on it, be sure to have the spark plug completely soaked with it.


Cleaning out the fuel injector shouldn’t be seen as a minor issue because a buildup of carbon and particles can trigger other problems in the engine.

Before adding an injector cleaner into the system be sure it is one that’s compatible with the system, if you are not sure about which one to use, you can always consult your car mechanic or check the owner’s manual. Better still, have the mechanic clean out the injector system for you.