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Discussion Starter #1
Having a debate on another forum (don't worry, it's not a rival, not even a motor based forum;) ) and seem to be getting different points of view;

What is worse/more expensive to repair and why? Is it filling up a diesel with petrol or visa versa?
 

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Still a Petrolhead but also like diesel
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2,311 Posts
Hi Scatz.... cant remember the outcome, but 5th gear did a test in the last series ... I'm sure that diesel fuel in a petrol engine was the least problematic ... after draining it was just a bit smokey for a while, where petrol in a diesel engine was a complete strip down ....

Lagdti will know the real life answer on this ... but you could check the 5th gear site.

:)
 

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Discussion Starter #3
Thanks truck but I wanted to hear it from a mechanics mouth (keyboard in this case) with the reason why its worse so I've got some ammunition to go back to 'tother forum.

You see, my arguement was that petrol in a diesel was worse but I had no info to back this up, me not being very mechanically minded an' all, but I had about twenty other bods telling me different, even though I know deep down that I'm right! Just ask the OH, she knows I'm always right, well that's what she leads me to believe, lol.
 

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did this myself when running a diesel peugoet & petrol espace youve guessed filled up the pug with petrol (had just come of nights so was nakad )got 500yds up the road before i felt the effects ended up dumping it in a car park & towing it home wouldnt run at all .drained it (with the likkle bulb hand pump took ages )filled up diesel hard to start but once running was fine after that for about two months untill it went bang on the M56 going to tranmere missed the game (got thumped 4 -0 ). the drained fuel went in the espace where apart from being a bit smokey ran fine so think petrol into diesel is worse off this evidance .
 

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Super Moderator
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petrol into a diesel

Hi Scatz - if the guys in the other forum even understood the basic principles of both petrol and diesel engines they would know the answer - and which is likely to be the worst outcome. Without being too technical - guess which engine has spark plugs and which has a higher compression ratio. Enough said - trying to run a diesel on petrol will definitely damage the fuel injection system and if it doe'snt give up first the engine will probaly seize or put a leg out of bed (in mechanics lingo that means either a piston or connecting rod will forcefully make its way through the engine block) wrecking the engine completely!:rofl: :rofl:
 

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Back in the good old days of mechanical injection, diesel engines were a lot more tolerant. Putting a reasonable proportion of petrol in with the diesel was actually a common method of stopping the fuel from waxing in low temperatures. Also, back then, it was possible to mix the fuels either way. People were just as likely to put diesel in a petrol as the other way round.

Now it's difficult to inadvertently put diesel in a petrol since they narrowed the filler neck on cars with catalytic converters. On top of that, the electronically operated high pressure systems such as 'common rail' and its equivalents rely on the lubricating properties of the diesel. Put petrol in there and the protection just dissolves.

This is where it can get really expensive on a modern diesel engine, as fragments of metal from the fuel pump can contaminate the whole system. In theory, the only guaranteed way to clear it out is to replace the whole fuel system, from the tank right through to the injectors. And of course that's not cheap.

A petrol system on the other hand, will probably be fine once the diesel is flushed out and a new fuel filter is fitted. The worst I'd expect to see is a knackered cat.
 

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Hi Horatio - your not far wrong I would agree - diesel would probably wreck the oxygen sensors as well and send the management sytem haywire. I've seen people trying to use home heating oil and modern diesels definitely don't like it. After all a little additive called silcone done quite a bit of damage - despite the retailers originally denying anyhing was wrong. I don't mind helping people and giving advice but I resent giving out information to help someone trying to "score points":crazy: on another forum. Seems a bit petty in my view. After all they could try "Wikipedia" or the "Howstuffworks" sites - loads of info out there if you only look.:)
 

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Hi Horatio - your not far wrong I would agree - diesel would probably wreck the oxygen sensors as well and send the management sytem haywire.
Good point. As the reports of the petrol problem have been saying, it's common practise to add silicon to diesel to prevent foaming. Whether or not a short run on diesel would be enough to contaminate the sensors is debatable, but there's certainly at least as much risk to the sensors as there is to the cat.
I don't mind helping people and giving advice but I resent giving out information to help someone trying to "score points":crazy: on another forum. Seems a bit petty in my view. After all they could try "Wikipedia" or the "Howstuffworks" sites - loads of info out there if you only look.:)
Fair enough, though I've no objections to being asked to help settle an argument, as long as I'm not expected to get directly involved with it. In fairness, we don't know what context the information is being used in. It could be a perfectly civil discussion to settle a difference of opinion.

Then again, this is the Internet :p
 

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Discussion Starter #15 (Edited)
Thanks coffee, and mad, don't start bitchin'. I'm a little old for point scoring, I have merely asked a question on a motoring forum where I thought I would get a half decent response from someone or some people that have half a clue what they are talking about unlike myself when it comes to deep mechanical issues and like the others that I am having the dispute/discussion with in the other forum. Seeing as the other forum is not in anyway car orientated I thought I would come here to gain some further insight and report back.
 

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Just to confirm the point,running a diesel engine on petrol will cause more damage (and therefore expense) than running a petrol car on diesel.

Diesel engines use the fuel to lubricate the pump(especially the high pressure pump on common rail diesels),and petrol offers very little in the way of lubrication!.

As for the argument that seems to have started,please pack it in.We have had enough petty squabbles over last few months,and they don't serve any purpose.I don't care who said what to whom,but I have seen a few posts lately that I have turned a blind eye to,can I please ask people to do the same.:eek:

Constructive discussion is helpful,petty arguing helps no one.

Thanks.:)
 
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