Misfuelling your vehicle is one of the most common car mistakes drivers make. It’s easy to make the wrong fuel choice, but when you realise you’ve put the wrong fuel in your car, you may wonder: is it worse to put petrol in a diesel car or diesel in a petrol car?
It’s more dangerous to put petrol in a diesel vehicle than it is to put diesel in a petrol vehicle. Diesel will coat the fuel system and spark plugs after you start your engine, which frequently results in misfiring. You risk having smoke come out of your engine, a cutout, or no start at all. The fuel system needs to be drained as quickly as can be.
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In this article, we’ll break down the consequences of each and explain which is the more dangerous mistake. We’ll also answer some frequently asked questions and offer solutions if you find yourself in this sticky situation.
Which Is Worse: Petrol in a Diesel Car or Diesel in a Petrol Car?
Filling up your car with the wrong fuel is one of the most frequent driving mistakes. If you’ve accidentally added the wrong fuel to your vehicle and are worried about the damaging effects, it is helpful to understand the dangers of having petrol in a diesel car compared to having diesel in a petrol car.
Between the two, putting petrol in a diesel car is considered the more damaging mistake.
The impact on the fuel system and engine is more severe, with the possibility of having to replace expensive components like the fuel pump, injectors, and fuel filters. On the other hand, diesel in a petrol car usually results in ignition issues and clogged spark plugs, but it is typically easier and less costly to fix.
Both mistakes can lead to misfuelling, which can be expensive to fix and could cause damage that lasts a long time.
But if you accidentally put the wrong fuel in your car, you need to act fast. If you accidentally put diesel fuel in a petrol car or petrol fuel in a diesel car, you should turn off the engine right away and call a professional to drain and clean the fuel system. This will help limit the damage and repair costs.
Key Differences Between Petrol and Diesel Engines
Diesel engines are compression ignition, and so they require high pressure and a fuel that lubricates as it goes. That lubricating effect is what you lose when you pour petrol in a diesel tank, they add, and the fuel pump and injectors can wear out fast.
You’re going to hear some terrible knocking, see plenty of smoke, lose power, and you might not even get your engine started once the wrong fuel starts circulating.
Petrol engines are all about spark ignition, and they crave a light, volatile fuel. Diesel is too heavy and doesn’t evaporate like petrol does, meaning that if you put diesel in a petrol car, it can lead to misfiring at best or rough running and even a clogged catalytic converter.
Petrol In A Diesel Car – The Damages
Most petrol pump nozzles are smaller than diesel. So this makes it easier to make the mistake when putting the wrong fuel in, as the nozzle will be able to fit in easily.
Here is a list of the damages:
- Diesel serves as a lubricant, aiding the fuel pump’s performance.
- Diesel engine friction is increased by petrol, which has the reverse effect.
- It’s bad news for your diesel engine because of the friction.
- The diesel engine will cause greater harm the more petrol is poured through it.
- It is crucial to avoid starting the car for this reason.
The improper fuel is particularly likely to harm common rail (or HDi) diesel engines. If there is a lot of damage, new fuel pumps, injectors, pipes, filters, and fuel tanks may be necessary.
Diesel In A Petrol Car – The Damages
It doesn’t actually fit because the diesel pump nozzle is larger than the majority of petrol filler necks. Because of this, it happens far less frequently to fill up a petrol car with petrol than with diesel.
Additionally, adding diesel to a petrol engine doesn’t do as much harm; thus, there is typically less damage.
The spark plugs cause the petrol to ignite by a spark generated from the plug
The fuel system and spark plugs are clogged up by the diesel.
In simple terms, the car won’t start.
How to Prevent Misfuelling
Stay Alert at the Pump: Always double-check the fuel type before refuelling.
Use Fuel Caps and Warning Labels: Many modern vehicles have fuel caps and labels to prevent the wrong fuel from being added.
Fuel Nozzle Adaptors: Some people use fuel nozzle adaptors to ensure the right nozzle fits into the fuel tank.
Long-Term Implications, Prevention, and Recovery
Engine and Fuel System Damage
Petrol in a diesel car wipes out the lubrication the pump and injectors need. That means more wear, and you could end up with a seized pump or stuck injectors.
If you drove for a bit, metal bits and heat might wreck seals and the high-pressure pump, and those aren’t cheap to replace.
Diesel in a petrol car is a different beast. Diesel doesn’t ignite easily in petrol engines, so you’ll get misfires, heavy smoke, and maybe a blocked catalytic converter.
If you keep driving, spark plugs, oxygen sensors, and the cat could all end up needing replacement.
Impact on Mileage, Emissions, and Driving Scenarios
The wrong types of fuel tanks affect your fuel economy, not to mention raising the emissions ratio. Any diesel engine converted to petrol no longer gets its nice burn, so you get rubbish fuel consumption and a lot more smoke and soot.
Cars running petrol with diesel will misfire, run rich and likely trigger the check engine light. You’ll fail emissions tests until you clean it up.
Things are even worse on short trips, as the engine never gets hot enough to incinerate soot, clogging the DPF more quickly.
That just adds stress to the tyre, and that’s even if you’re towing or hauling something heavy, which is going to make the damage come quicker.
Prevention Strategies and Steps to Take After Misfuelling
Best way to avoid this? Pay attention to the pump and bigger diesel nozzles, and most stations label things clearly. If you swap cars a lot, maybe slap a coloured tag or sticker by the filler cap as a reminder.
If you spot the mistake before starting the engine, don’t even turn the key. Call our professionals for drain and flush.
Call Now (24/7)If you realise you have committed misfuelling, follow these steps immediately.
- DO NOT Turn the Key
The most critical rule. Even turning the ignition to the “On” position (without starting the engine) can prime the electric fuel pump, circulating the wrong fuel through the system.
- Remove the Keys
Take the keys out of the ignition entirely to remove the temptation to check if it starts.
- Push, Don’t Drive
Push the car to a safe spot away from the pumps. Do not drive it to the side.
- Call for Help
You need our professional fuel drain service. Tell them specifically: “I put petrol in a diesel car” or vice versa.
If you have found yourself in one of these situations, then do not worry. Over 150,000 people a year misfuel within the UK. That’s roughly one every 3 minutes. So I wouldn’t be too ashamed, as you fall under a large category of people who make the same mistake.
After that, there are a few simple steps on what to do next.
Inform the petrol station staff
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Call your insurance provider
Frequently Asked Questions
If you have queries like “What happens if you put diesel in a petrol car?”, “What happens if you put the wrong fuel in your car?”, or “What happens if you put petrol in a diesel car?”, the answers typically involve engine misfires, clogging of spark plugs, and potential damage to the fuel system. Whether it’s petrol in a diesel car or diesel in a petrol car, both mistakes can cause ignition issues, poor engine performance, and costly repairs if not addressed immediately.
What Happens If You Put Diesel in a Petrol Car?
If you put diesel in a petrol car, the engine will likely fail to start or run poorly. Diesel doesn’t ignite in a petrol engine the same way petrol does, leading to clogged spark plugs and fuel lines. While it’s less damaging than putting petrol in a diesel car, it can still cause issues like misfires and poor engine performance. To fix it, the fuel system must be drained and cleaned.
What are the consequences of adding a small amount of diesel to a petrol car?
If you accidentally squirt a bit of diesel into your gas tank, your car likely will run rough, blow thick black smoke and lose power. It may run badly or be difficult to get started until the diesel is purged through it.
If you don’t try to start the engine, then your long-term safety is likely secure. But if you do, then a fuel system flush is probably in order, and that might include the spark plugs.
How far is it possible to drive a diesel car with petrol in the tank before damage occurs?
Honestly, don’t drive a diesel car if you’ve put petrol in the tank. Even a few miles can mess things up, since petrol strips away the lubrication those high-pressure diesel parts need.
If you absolutely have to move the car for safety, keep the revs super low and stop ASAP. Then arrange for a pro to drain the tank and check things over.
What should you do if one litre of diesel is accidentally put into a petrol car?
Don’t start the engine. If you keep the engine off, one litre mixed with a full tank of petrol probably won’t cause major damage.
Call our recovery service to drain the tank and check the fuel system. If you already started the car, turn it off, get it towed, and tell the mechanic exactly how much diesel you added.
Can I still drive my car if I put the wrong fuel in it?
No, you should not drive your car after misfuelling. If you’ve put the wrong fuel in your car, stop immediately and call our professionals to drain the fuel system.
Call Now (24/7)What should I do if I accidentally put the wrong fuel in my car?
If you realise that you’ve put the wrong fuel in your car, stop the engine immediately. Don’t attempt to drive the car. Call for roadside assistance or have the fuel system drained and inspected by a professional.
Is it common to put the wrong fuel in a car?
Yes, over 150,000 people in the UK make the mistake of misfuelling their car each year, which happens roughly once every 3 minutes.
Can petrol and diesel coexist in a fuel tank without causing separation issues?
Petrol and diesel do mix in the tank; they don’t separate like oil and water. But that mixture isn’t good for either engine type.
If you run on a mixed tank, you’ll get poor combustion in petrol engines and lose lubrication in diesel engines. Always drain the mixed fuel before driving.