Petrol in diesel car

[mechman]

Hi all.
I made an error today. Put a gallon of petrol (before I realised )in my diesel Octavia. Phoned my garage and was told not to drive it, fair enough, Phoned the guy that pumps them out and he said mixed with full tank of diesel it should be fine. I've driven it home (10 miles no symptoms yet). What does the Hive think?

 

[Trevorleach]

Hi all.
I made an error today. Put a gallon of petrol (before I realised )in my diesel Octavia. Phoned my garage and was told not to drive it, fair enough, Phoned the guy that pumps them out and he said mixed with full tank of diesel it should be fine. I've driven it home (10 miles no symptoms yet). What does the Hive think?

Methinks wrong thread?

 

[mechman]

Methinks wrong thread?

I agree, Mod please move it to the appropriate section.

 

[mechman]

It’s here, so I’ll answer.

Rather depends on how much the tank holds!

About 12 gals

 

[Trevorleach]

I would likely add about 250ml of engine oil, mixed with diesel at the earliest opportunity.

I've added a litre of petrol to a 45 litre tank before, without any worries - well mixed in, of course.

I expect the main risk is burning the nozzles with ignition too close at time of injection. Go easy on the engine for the time this fuel is in the tank. Diluting with more diesel ASAP is an obvious step to reduce any damage occurring.

The problem with petrol is is provides no lube to the high pressure diesel system, some of which runs at such high pressure and is built to such tight tolerances some parts actually have no traditional seals.
Hight pressure pumps and injectors are pretty expensive.

 

[dobbslc]

Some people run a bit of petrol in their older Toyota Hilux diesels when they use veg oil in the winter. The older ones have a mostly bombproof pump though…

 

[jmp49]

The problem with petrol is is provides no lube to the high pressure diesel system, some of which runs at such high pressure and is built to such tight tolerances some parts actually have no traditional seals.
Hight pressure pumps and injectors are pretty expensive.

Have personal experience of this in wife's dCi engined Clio iv estate grandtour after a suspected contanimanted fill up (not a misfuel) which resulted in the high pressure pump system dying and other things that went wrong in the resulting mess. I did some basic checks on a sample from the tank and no water contamination with colourkutt, but the "diesel" from the fill up dissolved polystyrene overnight and some clean diesel from a can didnt with a 2nd coupon from the same piece of polystyrene. Did some basic burn tests and very roughly estimated it at about 20% petrol.
My wife was on holiday in it 400km away and the garage it was recovered to ignored our requests to run fuel tests and quoted 4k for a turbo and FAP replacement, no mention of anything else. I felt like they were having us over because person on holiday, stressed out and putting her trust in them, and just hired a breakdown van and went and got it. Still running the same FAP it had in it, and a grand for a low mileage engine from the breakers. Pig of a job to swap though. The turbo impeller had snapped too, and the wheels were embedded in the housings and had sent shards of intake impeller into the intercooler and other disasters but there was several fault codes relating to the injectors and dci pump pressures. She rang me and told me it felt wrong after the fill up, like it was on 3 cylinders or something and I told her to put her foot to the floor to clear it out thinking it was egr related. And then a bang and then it was game over.
I would slip some oil in the fuel tank as another poster suggested...

 

[Bullet2012]

Apply to DVLA for a change to hybrid power so you receive a reduction in road tax .

 

[Turbo]

Did that before in my 406 hdi. Filled the tank with diesel and all was ok. You could smell the petrol in the exhausr fumes.
A couple of mechanics told me that it is a way to clean out the injection system, similar to redex.

 

[roofman]

should be fine, might even clean the injectors while its going through in dilated form

 

[cocker]

Brim it with diesel , it'll be fine .
Misfueling is mostly done by men , I put a FULL tank of petrol in our brand new vw transporter whilst "in drink" about 16 year ago . Mrs C paid , hopped in and said " I didn't realise this van was petrol " . 'kin dear couple of pints that was .

 

[mechman]

Diesel full to the neck, still not sure so got the guy to come and pump the fuel out, he gave the car a once over said it was running fine, checked the exhaust all fine, and he said if anything goes wrong I'll buy the car off you I was going to a place 30 miles from me and he followed me all the way, no probs. So back home now. It's done 70 miles since my misdemeanour all seems well. The guy did say to keep the tank topped up which I do any way. Hope I've been lucky.

 

[dieselsamurai]

To get our old Laguna through the MOT on emissions for the last 4 years we had it the only way was to run it low on diesel add half a gallon of petrol and passed every time , without it was borderline . Topped the tank up afterwards and no issues at all in fact probably cleaned the injectors as mentioned before

I think most garages will see pound signs as soon as you tell them youve done it but if it was only a small amount it wont cause any harm

 

[redlig]

Did exactly the same with my T4 ,about 5 ltrs of petrol . Filled the tank with diesel and carried on and never had a problem. In olden days we put petrol in to get better starting in cold weather . I realise the gubbins is a bit more specialised now but just keep on filling up for a few days to weaken the mix.

 

[Ubique]

The problem with petrol is is provides no lube to the high pressure diesel system, some of which runs at such high pressure and is built to such tight tolerances some parts actually have no traditional seals.
Hight pressure pumps and injectors are pretty expensive.

Modern (EU3 and on) Diesel high pressure pumps do not have bearings, they are machined so the rotors are suspended in diesel by precisely one molecule's width. Petrol has a smaller molecular size, which allows metal-on metal contact within the HP fuel pump, pushing shards of metal into the injectors, those that don't stick in the injectors go around again from the bleed-off line to the pump to get chopped up into smaller bits, then eventually they will get stuck in the piezo crystals in the fuel injector.... Most HP fuel pump bushings are made from PTFE as it's easier to machine to the very precise dimensions required.

It may well have been less damaging in older fuel injection systems (bar fusing the tips of the injectors, particularly Stanadyne ones used in old Transits) but not in any vehicle designed or made in this century.
This is why vehicle manufacturers mandate replacement of at least the high-pressure side, filter & fuel lines, possibly also the LP pump & tank if you wish to maintain any manufacturers warranty, it's also why diesel (and increasingly, petrol) fuel injection systems will shut off the fuel before the fuel system runs dry.

So you may 'get away with it' for now, but don't expect the fuel system to have the longevity you might expect.

 

[carbonarc]

During the UK winter diesel fuel for road vehicles has additives that will prevent fuel waxing down to -12 C.

 

[Ubique]

This is the contents of a fuel rail from a 2018 Tiguan, the owner had misfuelled four months previously and had been (correctly) advised not to drive and was recovered in. They refused the mandated repair and had the tank drained and fuel filter replaced elsewhere. Obviously it's had many tanks of diesel through it since.

This is the volume control valve, the swarf had jammed it and caused fuel pressure issues.

Parts replaced:-
High pressure fuel pump
Fuel injectors
Fuel rail
All HP fuel lines
All LP fuel lines
Fuel filter & housing
LP fuel pump module
fuel tank.

Obviously none of it was covered by the extended warranty, nor, as increasingly the case, by the owners car insurance.
I can't remember how much petrol they put in it - certainly not a full tank and they initially reported no running issues, it was only when the exhaust 'smelt funny' on getting home that they called roadside assistance.

 

[Dozzer]

Having designed diesel engines for over 10 years, 100% agree with @Ubique
The older system will survive, but a modern High Pressure common rail will not.
On the later V6 & V8 lion engines and the Panther 2 & 2.2l the rail pressures were as high as 32000psi. the tank lift pump will take it to around 140psi, then the piston pump normally on the end of the cam takes it to the high pressure, this is where no lube will kill it. we had a problem with the 3ltr V6 dieing in Russia, they have very poor quality diesel fuel and it was killing pumps in less than 3000 miles, Bosch had to design an upgraded unit.
If it was old petrol with Tetraethyllead and a bit of sulphur they will act as a lubricant.
With the amount of benzine and ethanol in modern petrol its more like a solvent.

 

[Ubique]

The fuel 'subtractives' in diesel are one of the reasons I've changed to a petrol engined vehicle - and I try to run that on E5 / 99RON where possible, purely to avoid the ethanol component, which is hygroscopic - not a great thing for fuel to have in it.
Aside from mis-phased HP fuel pumps, I've seen a failing HP pump strip the teeth from a timing belt, many months after being misfuelled.
Some of the essentials I always took to North Africa was a good stock of fuel filters, some cetane booster and inline sedimenter / seperators to attach to the barrel pumps we inevitably had to use at some point, although we always found Libyan fuel to be good quality (and dirt cheap!) compared to Tunisia, Morocco and Western Sahara / Mauritania.

I suspect I've been driving some of your test mules at some point

 

[Dozzer]

The fuel 'subtractives' in diesel are one of the reasons I've changed to a petrol engined vehicle - and I try to run that on E5 / 99RON where possible, purely to avoid the ethanol component, which is hygroscopic - not a great thing for fuel to have in it.
Aside from mis-phased HP fuel pumps, I've seen a failing HP pump strip the teeth from a timing belt, many months after being misfuelled.
Some of the essentials I always took to North Africa was a good stock of fuel filters, some cetane booster and inline sedimenter / seperators to attach to the barrel pumps we inevitably had to use at some point, although we always found Libyan fuel to be good quality (and dirt cheap!) compared to Tunisia, Morocco and Western Sahara / Mauritania.

I suspect I've been driving some of your test mules at some point

You probably have driven one of our mules, was part of team that worked with JLR putting 9H2Q it in the L319, L320 and X250 (did the intake on that) we had to raise and twist the turbos on both sides to clear the suspension turrets on the RRS/D4, but we did improve the crossover pipe mounting from the 2.7L just wish they didn't stroke the engine, that reduced the pin overlap making the crank that bit weaker, when the webs were already a compromise.