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One of my neighbours has just put £7 of petrol in his diesel car, realised his mistake and topped it up with another £50 of diesel. It was not quite empty, so at a guess 1/8th mix.
It is a very new car and he has to drive a long way tomorrow (to his Fathers funeral) and understandably he is not at his best, so only advice from those who actually know if it will cause any damage would be much appreciated please.
Thanks in advance
i did same thing in a works vehicle, then checked with fleet dept before i drove it away, they said not to and sent AA to low load it, AA man said the diesel lubes the ?fuel? pump, the car would drive but damage would occur to the pump resulting in failure at a later date which is very costly
edit - i know nothing about cars!!!
Modern day diesel pumps run to within a very close tolerance, so the lubrication quality of the Diesel is paramount to the longevity of the engine and its performance, Petrol in the tank no matter how much can have a major impact.
The missus put about a tenner of petrol in her diesel megane. Filled the rest up with diesel and it wasn't an issue.
should get away with that keep filling it up. Dont blame me if it blows up though.
Unless it's a fleet car and someone else will be footing the bill, no. It's not a case of it definitely breaking down tomorrow, but of being likely to break down prematurely in the future.
The fuel pumps are pretty sensitive, and can cost a fortune when they go. I believe it can be in the order of a £1500 bill. I would suggest any other option - get the AA to drain the tank, borrow or hire a car etc.
If he is an AA member, I suggest he gives them a ring and explains the situation. They may be able to sort it for him quickly.
I did similar a few years ago putting diesel in a petrol car, realised what I was doing and switched to petrol. Asked a mechanic if it would be ok, he said yes, but if I'd put petrol in a diesel car (even a small amount) he said I shouldn't even start it.
He may need a mechanic to drain the fuel line.
Technically speaking, he shouldn't even lock / unlock it. A lot of diesel cars start the fuel pump with the plipper key in order to avoid waiting for fuel pressurisation and glowplugs to warm up.
I would chance it personally. Your mate did the right thing by topping up with diesel. It might be a bit noisy and smoky due to the petrol being more explosive. Keep on filling up as often as pos to weaken the mix. The petrol also washes the oil off the piston bores, so don't do it to often.
I did it a few months back. Reckon i put £10 of petrol to £80 in diesel in my Transporter van.
So far so good. Kept it topped up for a few weeks.
Works fine. Might cough a bit on start up for a while but otherwise it will run fine.
In a modern engine I wouldn't even consider it. Very different in older engines, which I'm assuming is confusing some of the guys who think it'll be ok? It won't!
Thanks for the replies.
My first thought too was that if he keeps topping it up every 100 miles or so it would be ok but this was based on a London cab driver I knew who used to put in 1/2 gallon of petrol now and again to 'clean' the engine. IIRC it's a 320D BMW so not really comparable ! He drove it back from the garage (7 miles) with no problems so hopefully by topping up immediately he has managed to mix it so that no neat petrol got into the fuel system
I think he's going to drive it anyway as it's too late for other arrangements, so fingers crossed.
If you want you can add some 2-stroke oil to add the missing lubrication qualities, and maybe leave the cap off the tank to allow the move volatile petrol to evaporate.
Other than that get a local garage to drain the tank. DO NOT GO TO THE MAIN DEALER, and don't tell 'em, EVER. My wife filled my Berlingo with 60 litres of Unleaded. The local guy charged £50 to drain the tank and fuel lines. She wasn't going to tell me, but I noticed the £50 bill and asked what it was for...
Woody can you please give us an update after 12 months cos i don't believe the scare stories.... But could be proved wrong!
I'll let you know if he makes it there and back and any updates while I'm here but I'm renting so a 12 month report is unlikely.
Just to late to ask if the car was still at the pump!!
It's definitely the worst way round, but quite a weak mix. Didn't Top Gear do something similar with a BMW 330d they were racing? Oh no, that was their home made diesel that did the fuel pump in.
It's quite risky.
Had man old M red corsa 1.5 tdi many years ago. Did exactly the same thing and it ran fine. As others have said though that was an old diesel.
If he's used a 1 in 8 petrol/diesel mix, he will need to use 3-in-1 oil.
Pre-sperm, I find, is an excellent lubricant. Maybe he should produce some of that to help the car along.
I put a couple of litres in a 56plate galaxy. Brimmed it with diesel and it ran fine. Engine management light came on but went out once I'd used the tank and refilled with diesel. Was a hire car so can't comment on longterm problems.
My friend did it on a BMW 320d company car, except with a lot more petrol. The car got a few hundred metres and conked out. It cost 5k to fix and they replaced literally everything the petrol touched. Company car so they picked up the bill (minus 500 quid excess)
A mechanic friend brimmed his car with petrol, realised the mistake, poured a litre of 20/50 in and it was fine untill he sold it a year later.
For a question that you realize you need the correct answer to, why are you asking on a MTB forum?
TBH anyone on here posting about how they added petrol for anti-waxing in their Perkins prima engined Montego should just be quiet.
Modern diesel pumps are very different things to kind fitted to older cars. A common rail diesel engine can easily run at fuel pressures of 30,000PSI.
You're basically posting the equivalent of this:
"A mate's got some Fox forks, should he service them?"
"Nah, my open bath Marzocchis were fine, even after I didn't change the oil for 3 winters".
Ya £7 in £50 worth of Diesel not going to be a problem, Ive done it. Now water in diesel, thats another issue.
Modern diesel pumps are very different things to kind fitted to older cars. A common rail diesel engine can easily run at fuel pressures of 30,000PSI.
Exactly what he says.
Older diesels would if anything, benefit from a bit of petrol being chucked in with the mix (not too much mind). Petrol is a thinner, it helps thin the diesel slightly.
Modern diesel pumps run at ridiculous pressures though, and petrol in the mix is an absolute no go. It's also why you can run older non high pressure diesels (like the Pre-PD diesel in my VW Passat) on bio-diesel (or at least a mix of it and normal petro-diesel), whereas on a new common rail, high pressure diesel engine, you can't! You've got to run em on neat petro-diesel...
So whilst newer diesels generally produce higher specific outputs, and less CO2 per KM than an older diesel, they're potentially less environmentally friendly as you can in theory run older diesels entirely on someone else's waste products...
Did it myself in a three week old Audi (my first diesel)....stuck £15 worth of petrol, then topped it up with £50 worth of Diesel once I realised my error. Did not want to miss the first uplift at Fort Bill - so thrashed the car from Tyndrum without a thought for the life expectancy of the engine - just the need to be ready for 10.45am.
Car never coughed/farted for the next 88k miles I owned the vehicle.
So, a very mixed response as expected. I don't knowm when he's due back but I'll post up the outcome.
Waderider - do you really think the replies would have been any different on a car forum? I doubt it 😉
If it's commonrail - no, I'd syphon as much as possible out and re-load with D until I got it down below 5% ish. I'm not sure where that figure comes from, but >10% is a tad high for me.
If it's a non-commonrail, go for it.
320D .: it's commonrail.
As Leeph is the only one so far who has actually got real world experience of this rather than hearsay and doommongering (new word?) then i'm with him.
In fact the last time this came up a mechanic from a main dealer claimed that if someone brought a car in with this problem they would bill the owner for changing everything but in reality draining the tank, refilling and taking it for a spin..
As for asking for advice on here, everyone knows you only get the truth!
Or if enough people agree then hopefully they can't all be wrong (don't mention the Nazis!)
Mugaboo - if I was picking the tab up for the potential repair, not so sure I would have been so care free.
Not sure if the Audi was a commonrail - Audi 2.0 170bhp version?
Err...a friend, put 6 ltrs of petrol in my 02 freelander (It has a 2.0 BMW diesel engine). The mechanic who came to drain it reckoned 5 % would be ok, but anymore and there'll will trouble ahead. 6 ltrs was 10%. I pushed it away from pump and did not turn the key, so all petrol stayed in the tank. Erm, my friend felt pretty stupid afterwards.
Last time I serviced my car for the NCT (Irish MOT), my iutemised bill had eight quid's worth of petrol on it - the mechanic added it to help the car through the emissions test. Tank was near empty when I gave it to him, so I'd say it was running on a 50/50 mix, if not more. No hassle at all, not even a cough. And passed the test.
Right, thought i'd reply to this thread to give my story.
Three weeks ago I did the same to my wifes Golf TDI. In fact I put less petrol in - around £2 worth and topped the rest up with diesel. I did this because I have got away with it in the past with my own Renault Megane dci.
Around 40 miles later the turbo blew on her way home from work.
£1300 repair bill and the wife is still not talking to me. Happy with the not talking but £1300 is a lot of money!
Take from that what you will!
Neighbour is back and 700 miles later nothing to report and car is running fine.
If anything happens in the longer term I'll repost.
DCW - sounds unrelated. Fuel goes nowhere near the turbo.
Fuel goes nowhere near the turbo.
Petrol in the diesel does increase the exhaust gas temperature though. You can't run a derv turbo on a petrol engine for much that reason.
£2 worth tho? Plus, stock diesels are run way below dangerous EGT levels. That's why you can get so much more power with remaps.
DCW - sounds unrelated. Fuel goes nowhere near the turbo
less than 2l in a 55l tank...?!
No petrol will sit on top of diesel, when it runs out it will pull the petrol in and bugger the engine, one of the mechanics in my old work did it to 3 new cars and they all broke down at the exact same point while on way to new owner
No petrol will sit on top of diesel
Petrol and diesel mix - especially if you put 2l in first then mix it all up by adding 50l diesel...
We got our first diesel brand new last november. Not had it long and the wife put prob less than half a gallon of petrol in, then brimmed it on the advice of person at the petrol station she reckoned. It has now done 14k miles with no probs so hoping we've got away with it but you got me worried now!
Edit: from AA website:
Generally a small amount of incorrect fuel should not damage the engine as long as you have not started the car and top up fully with diesel fuel.If you've added more than 10% (5 litres in a 50 litre tank) petrol – Drain the tank and refill with diesel
If you've added less than 10% petrol (5 litres in a 50 litre tank) – Top up with diesel and run normally unless the manufacturer has advised otherwise