Diesel in a gasoline motor

LS21

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Nov 27, 2007
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theoretically, what would happen, if one was to theoretically fill ones tank with 1 gallon of diesel fuel, and then the remaining 9 gallons with 91 octane gasoline

and , theoretically, ones motor is a high compression 2 liter 4 cylinder motor

theoretically. what would happen
 

EightySix Four

Diamond Member
Jul 17, 2004
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Originally posted by: LS21
theoretically, what would happen, if one was to theoretically fill ones tank with 1 gallon of diesel fuel, and then the remaining 9 gallons with 91 octane gasoline

and , theoretically, ones motor is a high compression 2 liter 4 cylinder motor

theoretically. what would happen

Theoretically you would drain your gas tank.
 

cheesehead

Lifer
Aug 11, 2000
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Theoretically you'd make a horrible mess of the injection system and quite possibly destroy your engine.
 

Bignate603

Lifer
Sep 5, 2000
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Theoretically it may not run, would run crappy, or could do damage to it. It's not recommended.
 

Vette73

Lifer
Jul 5, 2000
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1 gallon will not do any real damage if you filled the tank with reg gas after that. Most small tanks are 12-13 gallons. So you are looking at around 8-9%. Will not run the best but as long as it was a one time thing don;t worry.
 
Mar 10, 2005
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Originally posted by: Marlin1975
1 gallon will not do any real damage if you filled the tank with reg gas after that. Most small tanks are 12-13 gallons. So you are looking at around 8-9%. Will not run the best but as long as it was a one time thing don;t worry.

1 gallon would lower the octane rating of the rest of the tank to the point of unusability. there would be a very good chance of catastrophic detonation.
 

Zenmervolt

Elite member
Oct 22, 2000
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Originally posted by: The Boston Dangler
Originally posted by: Marlin1975
1 gallon will not do any real damage if you filled the tank with reg gas after that. Most small tanks are 12-13 gallons. So you are looking at around 8-9%. Will not run the best but as long as it was a one time thing don;t worry.

1 gallon would lower the octane rating of the rest of the tank to the point of unusability. there would be a very good chance of catastrophic detonation.

Diesel is actually harder to detonate than gasoline. The problem with detonation comes from using gasoline in a diesel engine.

Diesel in a gasoline engine will cause problems with the injection system and generally requires draining the tank, though just one gallon in an entire tank may not do any lasting damage.

ZV
 

JulesMaximus

No Lifer
Jul 3, 2003
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Nothing, the car might not run and you'd probably have to clean out your fuel system but that's about it.
 

marvdmartian

Diamond Member
Apr 12, 2002
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When I worked for the Navy in Guam, we had a kid that mistakenly put diesel in the gasoline tank of his truck (someone had gotten lazy and put the wrong nozzle on that hose). I think he put close to 3/4 of a tank of diesel in the truck. It initially ran okay when he started it, but that was just burning the gasoline that was already in the fuel line. Once he hit the mix (about 1/4 to 1/2 mile away), it ran like crap, and needed constant throttle to keep it from stalling. It did not, however, blow anything up (except, perhaps, the temper of the mechanic that had to clean that mess up).
 

MadAmos

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Sep 13, 2006
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Up to 15-20% Diesel it will be down on power, hard to start and smoke a bit I have seen this several times when I owned an import auto repair shop a few years back and it is nothing to worry about. If you dilute it to under 10% you probably will not even notice it.
It may damage a catalytic converter especially if it is the higher sulfur versions the new ultra low sulfur Diesel would take a lot more to cause any damage.
 

Squisher

Lifer
Aug 17, 2000
21,204
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I got fired from a job as a hi-lo mechanic trainee for doing just this. I'm colorblind and the two shades of the pumps (green and red) looked awfully alike and that was all that differentiated them. :eek:

The only job I ever got fired from.

 

LS21

Banned
Nov 27, 2007
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theoretically, i pulled into a gas station and ran into the pisser while my theoretical friend who was theoretically drunk put a gal of Green stuff in the tank before it was noticed

total capacity is 13.2 so it is a bit less than 10% diesel as mentioned before

i drove it very very gently <3k rpm for 20 miles and didnt notice any problem. this morning i topped off the tank to dilute the mixture and it took 2.5 gallons (should be 1 tops)... so im thinking a good bit of the mixture just went straight through "the system" (diesel difficult to detonate)
 
Mar 10, 2005
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Originally posted by: Zenmervolt
Originally posted by: The Boston Dangler
Originally posted by: Marlin1975
1 gallon will not do any real damage if you filled the tank with reg gas after that. Most small tanks are 12-13 gallons. So you are looking at around 8-9%. Will not run the best but as long as it was a one time thing don;t worry.

1 gallon would lower the octane rating of the rest of the tank to the point of unusability. there would be a very good chance of catastrophic detonation.

Diesel is actually harder to detonate than gasoline. The problem with detonation comes from using gasoline in a diesel engine.

Diesel in a gasoline engine will cause problems with the injection system and generally requires draining the tank, though just one gallon in an entire tank may not do any lasting damage.

ZV

gasoline's octane rating describes its resistance to detonation (or knocking, dieseling) prior to spark ignition. diesel fuel has an octane rating of 20 - 25. in a hot, high compression engine, this could be more than the computer could compensate for, resulting in blown gaskets, bent valves, etc.

op, i'm glad your car survived the experience, theoretically.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
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Reminds me of that vid on one of those bad drivers shows.

A car is making a heavy smoke screen on a highway. Cops trying to find source of smoke screen as it's so heavy it's making it dangerous to drive. Cops catch up to new white 911 spewing smoke from exhaust. Driver frantically yells out:

"I've just put diesel in!"
 

JMapleton

Diamond Member
Nov 19, 2008
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theoretically this is an interesting thread. op could always siphin the gas out of the tank.
 

LS21

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Nov 27, 2007
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Originally posted by: The Boston Dangler

gasoline's octane rating describes its resistance to detonation (or knocking, dieseling) prior to spark ignition. diesel fuel has an octane rating of 20 - 25. in a hot, high compression engine, this could be more than the computer could compensate for, resulting in blown gaskets, bent valves, etc.

op, i'm glad your car survived the experience, theoretically.

it was my understanding that diesel is very resistant to detonation by pressure (and also ignition). i *think* diesel motors have compression ratio at the 20s:1 range. if it was the other way around, i would have added tons of octane booster in the tank. also, the car hasnt knocked or pinged yet
 

Pacfanweb

Lifer
Jan 2, 2000
13,155
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How did the dumbass put diesel in, anyway? The nozzle is WAY bigger, and won't go in a filler neck of a car that takes gas.

It's not going to knock....diesel is hard to ignite. Your mileage for this and the next tank or two will probably be off until the diesel is gone from the tank.
 

Zenmervolt

Elite member
Oct 22, 2000
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Originally posted by: The Boston Dangler
Originally posted by: Zenmervolt
Originally posted by: The Boston Dangler
Originally posted by: Marlin1975
1 gallon will not do any real damage if you filled the tank with reg gas after that. Most small tanks are 12-13 gallons. So you are looking at around 8-9%. Will not run the best but as long as it was a one time thing don;t worry.

1 gallon would lower the octane rating of the rest of the tank to the point of unusability. there would be a very good chance of catastrophic detonation.

Diesel is actually harder to detonate than gasoline. The problem with detonation comes from using gasoline in a diesel engine.

Diesel in a gasoline engine will cause problems with the injection system and generally requires draining the tank, though just one gallon in an entire tank may not do any lasting damage.

ZV

gasoline's octane rating describes its resistance to detonation (or knocking, dieseling) prior to spark ignition. diesel fuel has an octane rating of 20 - 25. in a hot, high compression engine, this could be more than the computer could compensate for, resulting in blown gaskets, bent valves, etc.

op, i'm glad your car survived the experience, theoretically.

Diesel doesn't have an octane rating. It has Cetane rating. Cetane rating works opposite of octane, a higher-cetane rating means it's easier for the diesel to self-ignite, while a low cetane rating means it's harder to self-ignite. So you're still incorrect. Diesel is more resistant to knock than gasoline. If you put gasoline in a diesel, the increased tendency to self-ignite of gasoline will cause severe issues.

Diesel's flash point is much higher than gasoline's. In fact, diesel is essentially an oil.

http://autorepair.about.com/cs/faqs/l/bl094g.htm
http://www.straightdope.com/co...instead-of-regular-gas


ZV
 

MikeMike

Lifer
Feb 6, 2000
45,885
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Originally posted by: Pacfanweb
How did the dumbass put diesel in, anyway? The nozzle is WAY bigger, and won't go in a filler neck of a car that takes gas.

It's not going to knock....diesel is hard to ignite. Your mileage for this and the next tank or two will probably be off until the diesel is gone from the tank.

This is what i came in here to post... a diesel nozzle is significantly larger than a gas nozzle...
 

jagec

Lifer
Apr 30, 2004
24,442
6
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Originally posted by: The Boston Dangler
zv, again i think we're on the same page while getting hung up on the details.

No, ZV is claiming that diesel is resistant to detonation and will not cause knocking in a gasoline engine, high compression or no. You claim that diesel is NOT resistant to detonation and WILL cause predetonation.

(I'm with ZV--diesel engines have a higher compression ratio, diesel is a heavier fuel oil vs. a volatile short-chain hydrocarbon.)
 

SickBeast

Lifer
Jul 21, 2000
14,377
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Fortunately, the gas would probably still burn.
Unfortunately, it would damage the engine.
Fortunately, the engine would still work enough to move the car.
Unfortunately, it could start to backfire and give you a headache.
Fortunately, most modern cars are reasonably soundproof.
Unfortunately, after a few minutes even a modern car would be rendered useless by doing something so stupid as this.

In theory, you should not put unleaded gas into a diesel motor.

/thread.
 

Pacfanweb

Lifer
Jan 2, 2000
13,155
59
91
Originally posted by: SickBeast
Fortunately, the gas would probably still burn.
Unfortunately, it would damage the engine.
Fortunately, the engine would still work enough to move the car.
Unfortunately, it could start to backfire and give you a headache.
Fortunately, most modern cars are reasonably soundproof.
Unfortunately, after a few minutes even a modern car would be rendered useless by doing something so stupid as this.

In theory, you should not put unleaded gas into a diesel motor.

/thread.
In theory, and unfortunately for you, you should re-read the OP, because you got it backwards.

And putting 1 gallon of gas in a diesel won't hurt at all....in fact, my Dad used to do that about once a month with his diesel truck. He'd put a gallon of premium, then fill it up with diesel.
It only lasted about 380k miles.

But the OP put a gallon of diesel in a gas car. Still waiting to see how his buddy managed that.