Why You Shouldn’t Wait to Replace a Loose Gas Cap

Why You Shouldn’t Wait to Replace a Loose Gas Cap

28th Sep 2020

gas cap on orange car

Check for a Loose Gas Cap

Does your vehicle have a loose gas cap? Being that it’s a small and simple component – typically consisting of plastic – you may assume that it’s harmless. All gas-powered vehicles have a cap that seals the gas tank. When it becomes loose, it will no longer create an airtight seal. As a result, a loose gas cap can lead to several problems when ignored.

Environmental Pollution

Driving your vehicle with a loose gas cap will contribute to environmental pollution. Gas may not necessarily leak out of the tank. Nonetheless, gas vapors will almost certainly leak out and into the atmosphere.You may even smell the distinct gas vapors when entering and exiting your vehicle. Gas vapors are hydrocarbons, and like all hydrocarbons, they can deplete the ozone layer.


A loose gas cap can trigger the Check Engine Light (CEL). Vehicles that use an engine control unit (ECU) with OBD-11 technology are designed to detect gas vapor leaks. If you have a loose gap, your vehicle will leak gas vapors. It may not occur immediately, but your vehicle’s ECU will eventually trigger the CEL in response to a loose gas cap.

Failed Emissions

If you live in a state or city that requires an annual emissions test, your vehicle may fail the test if it has a loose gas cap. Emissions testing requirement vary depending on the region. In many regions, however, the testing facility will check the integrity of your gas cap. They’ll remove your vehicle’s gas cap and connect it to a machine. The machine will then check to see if your gas cap is properly sealed. If it leaks, your vehicle will fail the test.

Secondly, you’ll often fail an emissions test if your vehicle has the CEL on. Other problems can cause the CEL as well. Whether it’s a loose gas cap or a failed catalytic converter, an illuminated CEL is often grounded for failure during an emissions test.

Poor Fuel Efficiency

You can expect poor fuel efficiency with a loose gas cap. Some reports suggest that driving with a loose gas cap will reduce fuel efficiency by as much as 10%. In other words, you can expect to pay up to 10% more when refueling your vehicle. A loose gas cap allows gas vapors to leak. Rather than entering your engine’s combustion chamber, these vapors will escape to the surrounding environment, thereby promoting poor fuel efficiency.