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  • Writer's pictureBrett Elliott

Are you overfilling your gas tank?

You may get a few more miles by overfilling your tank, but is it worth it?

Long story short... No.

The seemingly innate desire to give the gas pump just a few more 'clicks' is hard to overcome, but it comes with severe consequences. Those drawbacks include, potential damage to the EVAP system, sensors, and increasing emissions by defeating the vapor recovery nozzles found on all fuel station pumps.

Here's the inside scoop on why you should completely avoid those 'extra clicks' altogether.


Since the 1970's automobile manufacturers have been extremely concerned with emissions, with pressure from the EPA being the main driver. Manufacturers started designing systems to prevent fuel vapors from escaping the fuel tanks, as well as preventing fuel from leaking in case of a rollover. Viola!... enter the Evaporative Emission Control System (EVAP).

Flow of fuel vapors in EVAP system. As the EVAP Purge Solenoid rapidly cycles open/shut, it allows the engine to draw a slight vacuum on the fuel tank so it can ingest fuel vapors. An overfull fuel level can allow liquid fuel to be drawn into the system, potentially saturating components and rendering their functionality useless. Or worse, damaging them.


When that first 'click' happens while pumping gas, the tank is full. Filling past that point has a high likelihood of spilling over into your EVAP system, potentially saturating your pressure sensor, filling your vacuum hoses, and soaking your EVAP canister with liquid fuel.

DAMAGE: The vast majority of vehicle sensors are not designed to be exposed to liquid fuel. The potential outcomes of exposure are:

* FAILED Fuel Tank Pressure Sensor.

* FAILED Leak Detection Pump (LDP).

* FAILED EVAP Canister.

* FAILED Fuel pump (clogged canister, could collapse gas tank).

INCREASED EMISSIONS: Trying to force the fuel tank past full is overriding the gas pumps vapor recovery nozzle, allowing fumes to escape into the atmosphere rather than being recirculated back to the gas pump.

CHECK ENGINE LIGHT: Damage to any components will trigger your check engine light. Excessive fuel in the charcoal canister can potentially cause the engine to ingest additional fuel, causing running problems.


A the end of the day, all of the potential issues associated with trying to get that extra gallon isn't worth it. Especially when you're risking hundreds, or even thousands of dollars with your primary source of transportation.

#GermanAutohaus #Chattanooga #PSA #CarRepair #Overfilling

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