When you fill up at the pump, there's some implicit trust that goes into the transaction. After all, you're probably assuming the fuel that goes into your car's gas tank is the right kind. But what happens when it's the wrong kind of fuel, or even contaminated? 

Some Georgia residents found themselves grappling with this very question last year, as one Atlanta-area Kroger station sold water-contaminated gasoline, while another Kroger in the area sold diesel fuel from a regular gasoline pump. Both incidents happened within the same week, and in both cases, the mistake was only discovered after drivers had successfully filled their tanks with either the contaminated fuel or the wrong type of fuel for their vehicles.

Unfortunately, some vehicles were damaged as a result, leaving drivers wondering who to blame and how to recover the cost of the damage.

What happens when you use the wrong or contaminated fuel?

Getting water in your car's engine or accidentally using diesel fuel instead of gasoline can have a detrimental effect on your car's engine and performance.

Unlike gasoline, diesel fuel requires no additional assistance to ignite. Diesel also has a higher viscosity than gasoline, meaning it's thicker and denser. If a car designed to run on gasoline gets diesel fuel in its engine, it may run, but the diesel fuel will begin to clog the engine parts, including the fuel injector. Your car will become sluggish as it struggles to run properly with the heavier, thicker fuel. Eventually, the car won't start when it can't properly inject fuel into the combustion chamber. 

Diesel fuel in an engine will only cause permanent damage if the problem remains unaddressed. Fixing the problem can cost nearly $2,000, which includes the cost to drain and clean the tank of diesel fuel and to fix the fuel injection system.

If your car gets water into its gas tank, either through contaminated fuel or other means, your car may not start at all, as water can prevent the gasoline from igniting properly.

Cars with water in the fuel tank may also stall out on the road or have trouble accelerating. Cars are unlikely to suffer permanent damage from water in the gas tank but will need to have the contaminated fuel siphoned out.

Is bad gas covered by insurance?

Mechanical issues are often not directly covered by car insurance policies. However, Georgia residents may be covered by their insurance providers if they carry comprehensive coverage.

Comprehensive insurance covers incidents outside of collisions, such as theft, vandalism, acts of nature and falling objects.

In Georgia, comprehensive coverage is not required as part of the minimum liability coverage. Georgia drivers are required to have:

• $25,000 per person and $50,000 per accident for bodily injury liability
• $25,000 per accident for property damage liability

As such, Georgia residents who bought either contaminated gasoline or the wrong fuel may only be protected if they carry additional comprehensive coverage and if their provider covers damage from these types of incidents. Comprehensive coverage adds to the cost of insurance, so if you want to add it, your best bet is to shop around for the best possible rates.

What can you do as a driver to avoid these issues and get compensation for damage?

Unfortunately, the Georgia drivers had no way of telling the fuel was either wrong or contaminated with water. Likewise, consumers currently have no way to determine if they are receiving the proper fuel for their vehicles. Instead, they must trust the gas stations to offer the correct service for their vehicles.

However, cars with bad gas will begin to show warning signs fairly soon after the fuel gets into the tank. Difficulty starting your car after putting fuel in your tank is a sign you may have received the wrong type of fuel or fuel contaminated with water.

To get compensation, you'll need to verify the gas station did indeed sell you the wrong type of fuel or that the fuel was contaminated. This can be difficult, as it requires multiple complaints from different customers, an investigation into the fuel and an acknowledgment from the fuel provider that the gas was bad. The only way to receive compensation in this situation is either a successful lawsuit against the gas station at fault or through additional comprehensive coverage through your car insurance policy.

Maxime Rieman is Product Manager at ValuePenguin. Educating and assisting shoppers about financial products has been Rieman's focus, which led her to joining ValuePenguin, a consumer research and advice company based in New York. Previously, she was product marketing director at CoverWallet and launched the personal insurance team at NerdWallet.