What will happen if we put gasoline in a diesel engine?

Short answer: don't do it. And if you have already done it, go get it fixed ASAP to limit damage.

What happens when you use gasoline in a diesel engine? Either something expensive or something very expensive. Since gasoline is designed to be resistant to self-ignition, gasoline in a diesel engine either won't ignite or will ignite at the wrong time. Some diesel engines run leaner than gasoline engines (meaning that the air-fuel mix has a higher proportion of air than a gasoline engine). That increases the chances that the gasoline won't ignite and that unburnt fuel will be sent into the hot exhaust system--where, ironically, it could ignite, leading to possible exhaust damage. Even if you avoid that disaster, you can expect to pay $500 to drain the fuel tank, clean out the fuel lines, and refill the tank with diesel.

straightdope.com/mailbag/mdieselvsgas.html no longer exists
https://www.liveabout.com/accidentally-fueling-a-diesel-with-gasoline-85225

When you use gasoline in a Diesel engine the gasoline does not ignite properly and burns up too quickly and the result is very low power output.

I have done this by mistake and was forced to drain all the gas and replace it with fresh Diesel. I also had to "prime" the motor with WD40.

The result is slightly more than low power: to quote from the fixxer's reference 'Either something expensive or something very expensive'. You either blow the engine, or wreck the pump. Putting one cup of petrol to 20 gals of diesel won't do it, but one gallon to ten might be expensive. Yes, I've done it too, but I realised before I started the wagon up fortunately. Putting diesel in a petrol engine is also not recommended, as that article points out. On older engines, it can clog the carburettor or injectors (which are designed for the faster flow of petrol), and on newer ones I believe it can play heck with the engine control system for some reason,

Trying to use diesel fuel in a gasoline engine also has unpleasant consequences, but generally not as dire in terms of damage to the fuel system. Depending on the proportion of diesel fuel relative to gas in the tank, a gasoline engine will either run poorly or stop altogether, necessitating another $500 trip to the repair shop for draining and flushing. A couple of old grease monkeys at the shop I used to work at claimed that their "super high-compression" gasoline engines of the late 1960s could easily switch between gasoline and diesel fuel with no problems, but I tend to think they spent too much time inhaling fumes from the carburetor cleaning tank.

Nah. You just have to flush and drain.The motor will not ever blow from gas. A Diesel motor is twice as strong all around. Valves, crank, pistons, everything. They are hard to hurt. That is why they are used in trucks and the like (not to mention the torque [not horsepower] output). No damage will occur.

The pump is designed to pump a thicker more viscous substance, Diesel, so gas flows just fine. It is a gas pump that will be damaged by Diesel fuel.

It is no more than a pain in the nether region when this mistake is made.

I have actually driven a Diesel about a half-mile from the filling station FULL of gasoline and the only thing that told me I had made a mistake was the complete lack of power and throttle response. It was like driving a turtle!

Will it damage the engine? That depends on the amount added and the engine. There are two immediate impacts of diesel fuel mixed with gasoline: the octane is lowered and the fuel vaporization is reduced. The lowered octane may cause the engine to knock. Some engines have knock sensors and the electronic controls will adjust the timing and other engine conditions to try to control the knock. If the knock remains significant it can damage the engine by causing metal fatigue eventually leading to failure of critical parts like pistons, connecting rods, heads. Some very old engines (e.g. 1950's tractors) can accomodate lower octane, but the ones found in recent autos are normally running close to the knock threashold. The reduced volotitility caused by the added diesel will cause hard starting and will probably result in some unburnt hydrocarbons remaining in the exhaust gas from the engine; these may be reacted in the catalytic convertor causing it to overheat. A modern electronic controlled emission system controls the oxygen level in the exhaust gas going to the convertor so the significant increase in hydrocarbons with controlled oxygen may save the convertor, but will likely result in unburnt hydrocarbons exiting the exhaust. This will result in a smell and air pollution.

So if enough diesel is added to produce any of these problems it is a not a good situation. I would consider draining and replacing the fuel or if practical diluting it with fresh gasoline to eleminate the symptons.

http://www.faqs.org/qa/qa-8076.html

Placing Gasoline in a Diesel engine garners no damage unless one makes a habit of diluting the Diesel with a portion of Gasoline for long periods of time. Diesel fuel acts as a lubricant for the fuel pump so the Gasoline will, over time, destroy any seals in said pump. As for the engine. Diesel engines are built a lot tougher that Gasoline engines and therefore can take nearly any abuse one would subject it to.

The power/performance question....

Gasoline will not detonate properly (detonates prematurely) in a Diesel engine rendering the power output at next to nothing. Diesel in a Gas engine is actually not bad when done in a small ratio but straight Diesel will not burn properly in a Gas engine. All in all, if you filled your Diesel tank with Gas, drove a bit and found that there was a power problem, you must drain the gas tank, refill with Diesel then prime the air intake (use WD 40 NOT Starting Fluid!) and start it up and drive away!

Forget that it ever happened but be sure to learn from your mistakes! As for pumping Diesel into a Gas engine.....Diesel fill nozzles are MUCH larger in diameter and can not fit into a Gasoline fill neck but conversely it is easy to fit a Gas pump nozzle into a Diesel fill neck!

Yes it can be done, nozzles were (mixed up). I had to have the gas tank drained and flushed(2 hours on a Sundaynight, so I had to pay time and a half for a mechanic). I found outwhat I did before I started the engine so I didn't have any damage to it.

In my experience puttinggasoline in a diesel is worse than the converse, it would be best to siphon all the fuel you can out of the tank and refill with diesel, this should be sufficient, no need to pay a mechanic $500 to purge the fuel system. You may want to dump out the fuel filter(s) and fill with diesel or atf. On a gasiline engine if you fill the tank from empty with diesel fuel I would siphon it out and refill with gas, 25% diesel more or less I wouldn't worry about, I have used that with no ill effect for one tank.

I have just undergone this problem; I accidentally put Gas in my VW Jetta TDI 2011 Diesel Engine, I have had it for about a month, bought it brand new last Christmas, and this mistake happened me owning the car for less than a week, talk about Bad Luck. Had I known what I know now from my experience, I would have saved myself a lot of money. Not to mention avoid the scam of the dealership and the mental agony. I feel obligated to share my experience with you all, so you can get this problem fixed without the horrendous cost to you. This is for cars or trucks that are still under Dealer Warranty or have Full coverage Insurance.

Scenario:

Having put gas in my Diesel engine, I drove the car from the Gas station to my home which is about 5 miles, then I realized the mistake but it was too late. I called the dealership and told them my mishap and I was sent over a tow truck at no cost and was told “it is not a big deal” bring it over we will fix it.

Scam #1: This is NOT covered under warranty. Having Gotten to the VW dealership, I was told all we have to do is drain the Tank and replace the Filter and I will be good to Go; Scam # 2, you have to suck out the Gas from the lines, if need be use a compressor to suck it out, Drain the Tank and change the Filter is only good if you have NOT driven the car, once driven, this is almost never help full. The dealer made my car ready and charged me $650, before I could get home the car had its Coil light on and was not catching any speed. . I went back to the dealer and they said let us do it again as there may be some particles left, charged me another $650 (Total out of my pocket $1300). This did not fix it and I went back to the dealer and they said it is all messed up and gave me an estimate of $9950 which will NOT be covered by the warranty. Below is what I did, which the VW dealer said cannot be done (I claimed it on my insurance), but before you do that ready below Solution A, it is a better route than what I did.

Solution:

Here are the steps you need to take:

Solution A:

1. Do NOT drive the car as soon as you realize
2. Tow the car right away to a “NON-DEALER” Independent Diesel Mechanic or shop, do NOT use Roadside assistance, or else the Dealer at some point can nail you for it as that record is shared with the Dealership, Pay Cash from your pocket and an independently owned tow company, not even AAA.
3. Tow the car to a “NON-DEALER” Independent Diesel Mechanic or shop and clean up the Tank, usually should not cost more than $300 and this should fix the problem 9/10 times if you have not driven the car and 5/10 times if you have driven the car.
4. If the car is not fixed at the mechanic’s place at this point, then Tow the car back to your Home (Assuming it does not drive at all) this is imperative, however Ask the mechanic or shop to clean out all the Gas 100% regardless of if it is fixed or not.
5. If the car drives, fill up the tank with Diesel and drive at least 1 full tank, so all traces of Gas are gone.
6. Assuming the car is not fixed or barely fixed or not satisfied with the way it drives, then call the dealership while your car is at home and tell them your problem, DO NOT Mention you put “GAS” or else the warranty will NOT Cover and the dealer will love to scam you. Just mention the problem and “You don’t know how it happened, it just did”. This time use the Roadside assistance of the Dealership and tow the car to the dealership or drive the car to the dealership if it drives and let them do what it takes to fix it. Remember don’t be a “Smarty Pants” and let the dealership fix it, less knowledge is wise at this point. No Matter how much they say that there is Gas in there, remember you know nothing about this, they will try to make this into a “NON-Warranty” and try to make you pay for it. As far as you are concerned “The car is not working or working right and it is an engine problem, So FIX IT DAMN IT” put up a fight (Verbal) if need be and ultimately by law they have to fix it as this can never be proven, it could be the gas station has contaminated diesel or whatever, not your business. Be strong and smart or dumb whatever works.

Solution B:

Assuming you were an idiot like me, and believed in “Honesty the best policy”, then be ready to pay the price of honesty all the way to $10K, I am not rich and can barely make payments for the car, house, and “wife”, so here is what I did, having told the dealer 100% about the exact situation and to the minute details of what had happened.
1. Even though my Insurance agent advised me against it and the internet did not speak about this, the dealer said: “I have seen it numerous time, it will never happen, the insurance company will never pay”. The car was sitting at the dealership for over 3 weeks now, I figured what do I have to loose, (I have full coverage with Farmers) I called my insurance company. Believe me when I say, this was the easiest claim I ever filed; “a walk in the park” could not be easier. I was told I have to pay the deductible, and the adjuster went to go look at it, paid the dealership close to $10K and my car was fixed just as good as new. And Yes, I told the Insurance Company the whole scenario as to exactly how it happened taking full responsibility of the “accidental fuel contamination” (Key word for insurance claim). This can be done through your full coverage Insurance if Solution A above is not your option.

Good Luck, Its Pay Back Time Dealerships.

I have just undergone this problem; I accidentally put Gas in my VW Jetta TDI 2011 Diesel Engine, I have had it for about a month, bought it brand new last Christmas, and this mistake happened me owning the car for less than a week, talk about Bad Luck. Had I known what I know now from my experience, I would have saved myself a lot of money. Not to mention avoid the scam of the dealership and the mental agony. I feel obligated to share my experience with you all, so you can get this problem fixed without the horrendous cost to you. This is for cars or trucks that are still under Dealer Warranty or have Full coverage Insurance.
Scenario:
Having put gas in my Diesel engine, I drove the car from the Gas station to my home which is about 5 miles, then I realized the mistake but it was too late. I called the dealership and told them my mishap and I was sent over a tow truck at no cost and was told “it is not a big deal” bring it over we will fix it. Scam #1: This is NOT covered under warranty. Having Gotten to the VW dealership, I was told all we have to do is drain the Tank and replace the Filter and I will be good to Go; Scam # 2, you have to suck out the Gas from the lines, if need be use a compressor to suck it out, Drain the Tank and change the Filter is only good if you have NOT driven the car, once driven, this is almost never help full. The dealer made my car ready and charged me $650, before I could get home the car had its Coil light on and was not catching any speed. . I went back to the dealer and they said let us do it again as there may be some particles left, charged me another $650 (Total out of my pocket $1300). This did not fix it and I went back to the dealer and they said it is all messed up and gave me an estimate of $9950 which will NOT be covered by the warranty. Below is what I did, which the VW dealer said cannot be done (I claimed it on my insurance), but before you do that ready below Solution A, it is a better route than what I did.
Solution:
Here are the steps you need to take:
Solution A:
1. Do NOT drive the car as soon as you realize
2. Tow the car right away to a “NON-DEALER” Independent Diesel Mechanic or shop, do NOT use Roadside assistance, or else the Dealer at some point can nail you for it as that record is shared with the Dealership, Pay Cash from your pocket and an independently owned tow company, not even AAA.
3. Tow the car to a “NON-DEALER” Independent Diesel Mechanic or shop and clean up the Tank, usually should not cost more than $300 and this should fix the problem 9/10 times if you have not driven the car and 5/10 times if you have driven the car.
4. If the car is not fixed at the mechanic’s place at this point, then Tow the car back to your Home (Assuming it does not drive at all) this is imperative, however Ask the mechanic or shop to clean out all the Gas 100% regardless of if it is fixed or not.
5. If the car drives, fill up the tank with Diesel and drive at least 1 full tank, so all traces of Gas are gone.
6. Assuming the car is not fixed or barely fixed or not satisfied with the way it drives, then call the dealership while your car is at home and tell them your problem, DO NOT Mention you put “GAS” or else the warranty will NOT Cover and the dealer will love to scam you. Just mention the problem and “You don’t know how it happened, it just did”. This time use the Roadside assistance of the Dealership and tow the car to the dealership or drive the car to the dealership if it drives and let them do what it takes to fix it. Remember don’t be a “Smarty Pants” and let the dealership fix it, less knowledge is wise at this point. No Matter how much they say that there is Gas in there, remember you know nothing about this, they will try to make this into a “NON-Warranty” and try to make you pay for it. As far as you are concerned “The car is not working or working right and it is an engine problem, So FIX IT DAMN IT” put up a fight (Verbal) if need be and ultimately by law they have to fix it as this can never be proven, it could be the gas station has contaminated diesel or whatever, not your business. Be strong and smart or dumb whatever works.

Solution B:

Assuming you were an idiot like me, and believed in “Honesty the best policy”, then be ready to pay the price of honesty all the way to $10K, I am not rich and can barely make payments for the car, house, and “wife”, so here is what I did, having told the dealer 100% about the exact situation and to the minute details of what had happened.
1. Even though my Insurance agent advised me against it and the internet did not speak about this, the dealer said: “I have seen it numerous time, it will never happen, the insurance company will never pay”. The car was sitting at the dealership for over 3 weeks now, I figured what do I have to loose, (I have full coverage with Farmers) I called my insurance company. Believe me when I say, this was the easiest claim I ever filed; “a walk in the park” could not be easier. I was told I have to pay the deductible, and the adjuster went to go look at it, paid the dealership close to $10K and my car was fixed just as good as new. And Yes, I told the Insurance Company the whole scenario as to exactly how it happened taking full responsibility of the “accidental fuel contamination” (Key word for insurance claim). This can be done through your full coverage Insurance if Solution A above is not your option.

Good Luck, Its Pay Back Time Dealerships.