Accidentally put a bit of unleaded in my diesel car, does it matter? - HotUKDeals
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Accidentally put a bit of unleaded in my diesel car, does it matter?

Dantooine Avatar
1y, 10m agoPosted 1 year, 10 months ago
A couple of weeks ago I went to fill up my diesel car (fuel warning light had been on a while so low on fuel), and for some reason started filling with super unleaded! I had only put in about 90 pence worth when I realised so not a lot.
Not being one to worry too much about anything I then topped up with about £40 worth of diesel in the hope it would all get mixed up and be fine.
And the car was fine and has been since. But someone has mentioned to me it could still be an issue, potentially affecting parts in the engine, or if the unleaded doesn't mix and sits at the top, or bottom of the tank.

Is the small amount of petrol anything to worry about?
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Dantooine Avatar
1y, 10m agoPosted 1 year, 10 months ago
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#1
I'd have filled it all the way to be sure, but i'm sure it'll be fine.
#2
I have done this a few times my car being diesel and my wife's being petrol, never had any probs but I have always filled up after I put a bit of the wrong fuel in. last time I put £5 of petrol in my diesel then had to put £65 worth of diesel in, much to my dissatisfaction.
#3
Write off
#4
It will not do any harm, in fact in very low temperatures, it can actually help, it helps to stop the diesel from freezing.
#5
jonherb
Write off
. LOL you have helped the nerves
#6
You'll be fine.
#7
what car do you have?

EliTom
#8
For 90p worth you should be fine,like someone else said adding petrol to diesel stops it from freezing which is what some people do in their lawn mowers but really only useful if you live in the artic :) you may notice abit of white smoke when you get to the bottom of the tank but I'd try and keep as much diesel in it for awhile now
#9
knowing which car is important!

yes it's only about 2.5% mix but modern common rail diesel engines rely very much on the lubrication properties of diesel and this is removed by petrol.

so OP - which car? then I can give you some better / more informed information ..... rather than just you will eb OK / write off !

EliTom
#10
omg sell the car.
the engine will now only last 900,000 miles rather than the 999,999 miles
#11
if older car it will help clean you injectors so just fill it right up with diesel .
#12
it will be fine.
#13
in norway they add petrol to diesel. its called winter diesel.so you car will be ok
#14
I done the same and was petrified to tell my husband as he is a mechanical engineer and was expecting a lecture but he said as it was such a small amount doesn't do any harm and said they often do it in colder climates anyway!
#15
elitom
knowing which car is important!

yes it's only about 2.5% mix but modern common rail diesel engines rely very much on the lubrication properties of diesel and this is removed by petrol.

so OP - which car? then I can give you some better / more informed information ..... rather than just you will eb OK / write off !

EliTom
2005 Astra 1.9 CDTI
#16
Thanks all, sounds like nothing to worry about then :)
#17
Dantooine
Thanks all, sounds like nothing to worry about then :)

hmm maybe ...

astra 1.9 cdti is a high pressure common rail diesel injection system - Bosch high pressure fuel pump - it is a version of Fiat's uniJet Turbo Diesel .... one of the first common rail diesel engines.

the problem here is that the high pressure fuel pump runs with extremely tight tolerances and lubrication is provided by the oils in the diesel fuel. Petrol trips these oils out of the diesel for want of a better terminology - try putting a bit of diesel on your hand and feel how oily it feels - now wipe your hand with a bit of petrol and note that the oily feeling has gone. Even running a high pressure fuel pump with a small amount of petrol can cause serious wear in the fuel pump and hence a failure at a later date. The same can happen if you run the car out of fuel - the pump will run dry for a short time - this is enough to cause permanent damage.

So it kind of pot luck really - you maybe lucky or you may have cause some premature / serious wear in the high pressure fuel pump.

Your call really - but yes there is some risk.

EliTom
#18
Not that I've ever done it, but what about the other way around, a small amount of Diesel in a Petrol engined car?
#19
if it still drives then no problem isn't it?
#20
darkovo
Not that I've ever done it, but what about the other way around, a small amount of Diesel in a Petrol engined car?

in theory not quite as bad, the diesel will wax up injectors, but petrol will in theory wash the wax away

BUT unless it is a very old car it is neigh on impossible due to the smaller filler neck on a petrol car fuel tank. You would really have to put diesel into a unleaded fuel can then put it in the car tank ......

on very modern cars with direct injection gasoline engines the diesel will most likely clog the filters / injectors and the car will not run. if it does run then damage will occur to the catalyst and lamda / oxygen sensor - both are expensive to replace !

No real experience of this scenario because it is near impossible to re-create

EliTom

Edited By: elitom on Jan 13, 2015 17:59: .
#21
mutley1
if it still drives then no problem isn't it?

read post number 17

EliTom
#22
I used work for a fuel company and we were always told tell the customer to keep the tank topped up for a while to dilute the petrol and its fine. 90p worth though, id say ur alright. diesel engines are hardy.
diesel in a petrol engine is a disaster though.
#23
it will be fine but would suggest you pop into your local auto accessory shop or fuel station and by a bottle of diesel fuel addative and pop that in the tank.
#24
jonherb
Write off

Not only a write off but huge fire hazard that will go up in a ball of flames while you're driving along the motorway. Wouldn't worry about it, if it had been the other way round then maybe but dont forget next time :D

My fiesta and newer model fords wont let you put the wrong fuel in, on the diesel will fit in mine and petrol in my other halfs car thankfully.
#25
deiseaj058
I used work for a fuel company and we were always told tell the customer to keep the tank topped up for a while to dilute the petrol and its fine. 90p worth though, id say ur alright. diesel engines are hardy.
diesel in a petrol engine is a disaster though.
Never did my xr3 any harm , had the car a good few years after filling it with diesel with no problems
#26
snoopy18
deiseaj058
I used work for a fuel company and we were always told tell the customer to keep the tank topped up for a while to dilute the petrol and its fine. 90p worth though, id say ur alright. diesel engines are hardy.
diesel in a petrol engine is a disaster though.
Never did my xr3 any harm , had the car a good few years after filling it with diesel with no problems

and the same logic holds true for modern engines?

EliTom
#27
I put £20 worth of petrol in the wifes diesel focus the night before our wedding. It was midnight the night before our wedding we were driving back to her hotel after a family party and her car was low on deisel. I got out to fill her up with £20. my cars a petrol car so didnt think about it. We got about half a mile down the road and the car started juddering badly so we pulled over and she asked me what fuel id put in. So after a telling off we phoned the RAC for them to come to our rescue. They dont cover wrong fuel so it cost us £300 to get the car flushed out and the fuel system bled. 2 hours later the car was luckily running fine again. If we had of been with green flag it would of been free. We also lost the £20 of fuel and what was in the tank and also had to pay for the fuel he put in the car to get to the petrol station.

After that we still got married and while we were wating for the RAC we updated my speech for the following day
#28
No problem with that small amount
#29
elitom
snoopy18
deiseaj058
I used work for a fuel company and we were always told tell the customer to keep the tank topped up for a while to dilute the petrol and its fine. 90p worth though, id say ur alright. diesel engines are hardy.
diesel in a petrol engine is a disaster though.
Never did my xr3 any harm , had the car a good few years after filling it with diesel with no problems


and the same logic holds true for modern engines?

EliTom


Stop scaremongering, the small amount involved will do no harm.
#30
This ^^^

If it's fine now then it'll stay fine. I'd keep topping it up with diesel though to keep reducing the (already small) percentage of petrol.
#31
With 90pence worth it should be fine. Had you topped up a few litres you would have needed to drain the fuel tank, but as other have said, just keep topping up with diesel and you should be fine
#32
Cheers all, I'm not worrying now. May pop into my local garage to ask their opinion
#33
Dantooine
Cheers all, I'm not worrying now. May pop into my local garage to ask their opinion
Wouldn't even do that as depending on garage will see you coming as its work :)
#34
Just put in 6.2 litres of unleaded petrol into a diesal mini bus. When realised the error topped up with 51.94 of diesal. Should we worry???
#35
elitom
darkovo
Not that I've ever done it, but what about the other way around, a small amount of Diesel in a Petrol engined car?
in theory not quite as bad, the diesel will wax up injectors, but petrol will in theory wash the wax away
BUT unless it is a very old car it is neigh on impossible due to the smaller filler neck on a petrol car fuel tank. You would really have to put diesel into a unleaded fuel can then put it in the car tank ......
on very modern cars with direct injection gasoline engines the diesel will most likely clog the filters / injectors and the car will not run. if it does run then damage will occur to the catalyst and lamda / oxygen sensor - both are expensive to replace !
No real experience of this scenario because it is near impossible to re-create
EliTom
Neigh on impossible means there's always a possibility....:{

http://www.birminghammail.co.uk/news/midlands-news/asda-apologises-after-wrong-fuel-10336860.oO
#36
Mazscl2016
Just put in 6.2 litres of unleaded petrol into a diesal mini bus. When realised the error topped up with 51.94 of diesal. Should we worry???
Drive it as normal and once the fuel gauge is half way just fill it up again to the top.
#37
90p worth is about a thimbleful isn't it? :{

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