DIESEL IN A GAS CAR:
THE SURVIVAL GUIDE
It happens to thousands of drivers every year. However, the difference between a $200 flush and a $5,000 engine rebuild is what you do in the first 60 seconds.
Why Diesel and Gasoline Don’t Mix
Gasoline and diesel fuels are refined for two completely different combustion methods. Gasoline is designed to be thin and highly volatile, igniting via a spark plug. Diesel, on the other hand, is much thicker (more like a light oil) and is designed to ignite under intense compression. Because of these chemical differences, a gasoline engine simply cannot “digest” diesel fuel.
The Immediate Symptoms
If you have already started the car and driven a short distance, you will notice the following red flags almost immediately:
- Excessive Smoke: Because diesel is heavier, it won’t burn cleanly in a gas engine, leading to thick, dark smoke from the exhaust.
- Violent Misfiring: The spark plugs will struggle to ignite the oily diesel, causing the engine to shake or jerk.
- Loss of Power: The vehicle will feel sluggish and eventually stall as the thick diesel clogs the fuel injectors and coats the spark plugs.
The Golden Rule: Do Not Start the Engine
If you realize your mistake while still at the pump, leave the car off. If the engine never starts, the diesel stays in the tank. A mechanic can simply drain the tank and flush it for a few hundred dollars. However, once you turn the key, the fuel pump pulls that thick diesel into the fuel lines, the injectors, and the engine. This can lead to catastrophic damage to your fuel pump and catalytic converter, pushing repair costs into the thousands.
WHAT TO DO NOW
1. Stop: If you are driving, pull over safely and shut down the engine immediately.
2. Tow: Do not attempt to “dilute” the diesel by adding more gas. Call a tow truck to take the car to a reputable shop.
3. Document: Keep your fuel receipt. While rare, occasionally stations accidentally fill their underground “Regular” tanks with “Diesel” from the distributor, in which case you may be entitled to compensation for repairs.
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