Diesel and gasoline engines use distinct fuels and, as such, are fundamentally different in how they operate.
Gas stations use incorrectly sized nozzles to help ensure the proper use of fuels; However, even with the different-sized nozzles, an incorrectly sized gasoline nozzle can be technically inserted into a diesel vehicle’s fuel tank.
After all, putting incorrect engine oil in your vehicle isn’t recommended, but using fuel that is completely wrong for the type of engine can cause something different altogether.
What would happen if you put gasoline in a diesel engine? More importantly, what are the things you should do and not do when this happens?
Gasoline vs Diesel
There are many key differences between gasoline and diesel fuels in terms of their composition/functional mechanism. The most obvious difference is how they are ignited.
With gasoline, the fuel combusts when a spark from a spark plug is applied, and the timing is right. With diesel fuel, the fuel combusts simply from the high pressure created by the engine’s combustion chamber.
In terms of overall volatility, gasoline and diesel fuel are also rated by different overall metrics.
Gasoline fuel is given an overall octane rating, which generally starts between 87-90+ (87 being a “standard” grade), and diesel fuel is given a cetane rating, which falls between 40-55.
Diesel fuel typically burns more slowly than gasoline, but creates a higher energy output for every ignition of the fuel.
While varying by specific application, diesel combustion is generally thought of as 20 percent more efficient in terms of volume than gasoline. This is what creates the much higher torque associated with diesel-powered engines.
Immediate and Short-Term Effects (of Gas in a Diesel Engine)
Several short-term effects often occur when adding gasoline to a diesel vehicle’s fuel tank. The most significant short-term effects are as follows:
#1. No-start/Stalling.
In many cases, a diesel vehicle will start to run poorly shortly after putting gasoline in the tank. This typically leads to it eventually stalling, which is then shortly followed by an inability to restart after stalling occurs.
At this point, fuel system damage and internal engine wear have usually already occurred.
#2. Pre-ignition/Detonation.
The addition of gasoline to a diesel engine is also likely to cause a condition called pre-ignition or detonation.
Pre-ignition occurs because of ill-timed combustion from heat created during the high compression experienced by the diesel engine. Pre-ignition is known to cause serious engine damage internally, among other issues.
#3. Fuel-system Damage.
Diesel is naturally lubricating, whereas gasoline is not, so the diesel creates extra lubricating oils that will pass through other components of the fuel system, like high-pressure fuel pumps.
Without this lubrication, serious damage could occur in just a few minutes.
Long-Term Effects (of Gasoline in a Diesel Engine)
In addition, there are numerous indirect effects that are generally associated with mistakenly filling a diesel-powered vehicle with gasoline. These effects can take years to show; however, the long-term consequences are something to keep in mind.
#1. Fuel Tank Delamination.
Most diesel fuel tanks are lined to avoid deterioration of the tank material. When gasoline contaminates the fuel system, it is well known that these coatings deteriorate rapidly.
This could spell serious consequences for the health of your vehicle’s fuel system in the long run. In some cases, issues may not appear for 1-2 years.
#2. Residual Internal Engine Damage.
Another concern with the fuel system being contaminated with gasoline is the potential for internal engine damage that may not be immediately visible.
Just because the owner/operator does not notice any abnormal or accelerated engine wear, it does not mean they could not have internal engine damage.
There are cases where damage may be very minor initially but may continue to worsen over a longer period of time.
What To Do If You Put Gas Into A Diesel Engine
If you suspect you’ve added gasoline to a diesel fuel tank, there are a few things to keep in mind:
- Do Not Start The Vehicle – If you even think you may have added gasoline into a diesel-powered vehicle, do not start the affected vehicle. Avoid even placing the ignition in the “on” position; doing so will compromise the fuel system.
- Drain Fuel Tank – Next, drain the fuel tank of the affected vehicle completely. In some cases, you will have to drop the fuel tank to drain it.
- Flush Tank With Diesel Fuel – Even after you have drained the vehicle’s fuel tank, it is still advised to flush the tank with clean diesel fuel to make sure no residual gasoline remains.
- Fill With Diesel Fuel – After everything has been done, fill the vehicle with new diesel and attempt a start-up.
If the vehicle has been started already and you are driving, pull over and turn out the ignition – do not attempt to start the vehicle again and get a tow to the nearest trusted service center as soon as possible.
Insurance and Warranty Implications
There are a number of warranty/insurance implications that are normally associated with a diesel vehicle being the victim of mis-fueling.
In almost every scenario, the vehicle manufacturer’s warranty for whatever powertrain warranty remains is void, as it is.
This is also no coverage for any assistance in the repair of any damage, in the first place, incurred from the fact that mis-fueling had taken place in the first place, and that was simply under normal vehicle operation!
Likewise, it would be doubtful that your policy would provide coverage for policy costs from mis-fueling above, particularly if your individual policy was simple liability coverage.
Even policies with full coverage have exclusions for mis-fueling or “neglect”, an absence of attention and/or reasonable “care.”
Why Are There So Few Systems To Avoid Fueling Mistakes?
As it stands, very few mitigations are in place to avoid mis-fueling diesel engines.
This is probably in part due to the assumption that human error is not an issue here (which isn’t always true) and in part because of the increased costs that would potentially be passed on to fueling stations and/or vehicle manufacturers to mitigate human error.
As of now, the best mitigation in place to prevent these tragic incidents from taking place is through refueling nozzle diameter differences between gasoline and diesel fuel systems.
In most cases, a diesel fuel nozzle will not fit into a gasoline fuel tank filler neck, however, a gasoline fuel nozzle will fit into a diesel fuel tank filler neck, though very loosely and ill-fitted.