Hi All

I guess the title says it all. After 8+ years of driving a diesel I managed to do something that I have never done before - put 15L of unleaded into my nearly empty Oktavia TDI.

I then drove it for about 5 miles or so, stopped, tried to restart and it wasn't having it - the starting hasn't been great recently (maybe a subject for another post when we've figured out this issue) so I cranked it several times until it dawned on me when I checked the receipt from the filling station, that I was muppet-in-chief for the day. Doh!

So I guess the 5 miles will have been using up the diesel in the fuel line.

Questions:

1. Can I drain & flush the fuel system myself or is it a dealer job?

2. Am I likely to have landed myself with a big bill for injectors?

Any / all answers gratefully accepted, I'll even cope with the ribbing I guess I am about to take :-)

Thanks!

Fill the tank with diesel. Change your fuel filter and see what happens.

OK, thanks for getting back to me so quickly .... that was kind of my 1st reaction having heard of others do this from time to time.

If there's an issue with the injectors, is that going to cause any knock-on effects?

As long as you've avoided petrol going into them, should be reasonably ok. Drain the lot, fill with derv, fingers crossed

Hmmm, thanks for that, WW_VRS.

I thought I would be the only one on this forum at this time of night!

I guess my concern is that having turned the engine over several times, at least some unleaded will have found it's way into the injectors / cylinders.

Beyond the fact that I know petrol + injectors = bad (!) I don't really know what the likely effects are & therefore if / when the guys at the local dealership do the collective drawing in of breath and shaking of heads, whether the advice I get will be the voice of reason or the voice of avarice!

Having some info to play with is not just about knowing what to do next, it's partly about empowerment - if this was a £7k racing cycle, I'd know the answers, but as it's got an engine, I'm not so clued up - embarassingly enough for someone who teaches bicycle frame and component engineering & technology for a living ....

This kind of thing happens, annoyingly :(

Someone more technically experienced will probably be a long in a good few hours, hopefully it will be ok to wait for their advise just to be safe

I can't believe after all these years I could be so half-witted.

Oh, well, live & learn as they say!

Sincere thanks to both of you, back in the morning, I guess!

ATB, Graeme

What engine do you have?

Hi Lummox, it's the 1.9 TDI 105 hp

I just noticed, Lummox, you are in Newport Pagnell ... I'm in Olney :-)

If you've gone so far as to keep on cranking it then IMHO you're in for a rocky ride. Perhaps not immediately, but certainly in the medium-long term.

Petrol is a solvent and diesel is a lubricant, neat petrol in a diesel can do untold damage to seals etc as they're not designed to cope with petrol.

Having said that, in cold countries (certainly with the older diesels, not sure about the advice for PD and newer) you could put a certain amount of petrol in with the diesel to stop it from freezing.

I'd probably empty the tank, change the fuel filter and brim it with diesel. If you can bleed the lines of the petrol that's in there I'd do that too, although I don't know how hard that'll be. Theoretically you could just keep cranking as it's a self bleeding engine but I would minimise the risk wherever I could if I were you.

Best of luck

When you put the new fuel filter in, pour some derv into it, so that the engine isn't cranking on air and gets a nice dose of derv.

Put in a double dose of something like the millers powersport 4 into the tank when you fill it up with derv. This has extra lubrication in it and will hopefully counteract the cutting actions of the petrol.

Also every time you see the tank getting down to 3/4's go and top it up with fresh derv.

FWIW modern Ultra Low sulphur derv is much less lubricating than the old "proper" derv, so you might well find yourself lucky.

Worth contacting Lummox if you're unsure and close to him as he's a well respected VAG master Tech

This is all brilliant advice, guys, and thank you all for your help so far ...

I don't think VAG recommend using petrol as an anti-waxing agent (which I can remember doing years and years ago, before I owned a diesel myself) in their diesels, I seem to remember reading that on the net ages ago, but I'm still quietly praying that Shark_90 is being unduly pessermistic - I guess I'll find out later on today!

I think I need to go see Lummox in any case as there was a pre-existing problem with (I think) the MAF sensor, so hopefully if I can get the old girl rolling without any issues arising from this piece of idiocy, we can look at the next problem :-)

I'll keep the forum up to date so that any others who do something similar in a senior moment will at least be reassured / not reassured (depending on outcome ...)

Edited 17 February, 200917 yr by graemefk
bad grammar

Oh happy day!

I've drained the tank, flushed the fuel lines as far as I can, fitted a new filter with the filter can full of Derv and joy of joys, everything seems to run fine with no new noises, no sign of poor or lumpy running and idle is as quiet as this engine ever is & the indicated idle speed looks rock steady & bang on 900 rpm.

So in the immediate term, with the greatly apprecaited help of Lummox, Shark_90, Cheezemonkhai, WW_VRS and Decron, it looks like I may have gotten away with it unless there is anything else that I should be looking for, given my limited knowledge of diesels?

OK, Lummox, now all we need to do is have a chat about that "maybe MAF" problem ...

Once more, thank you all very much indeed, I greatly appreciate the time and effort you've all taken ...

You should be ok now, just get it over to Unit 18 at some point soonish, so Ross can give it a good once over to make all is well. I reckon it probably is though

Handy to have him nearby

This is all brilliant advice, guys, and thank you all for your help so far ...

I don't think VAG recommend using petrol as an anti-waxing agent (which I can remember doing years and years ago, before I owned a diesel myself) in their diesels, I seem to remember reading that on the net ages ago, but I'm still quietly praying that Shark_90 is being unduly pessermistic - I guess I'll find out later on today!

Glad to hear it's up and running! I must admit I'd probably be looking to move it on sooner rather than later but that's just me

Oh happy day!

I've drained the tank, flushed the fuel lines as far as I can, fitted a new filter with the filter can full of Derv and joy of joys, everything seems to run fine with no new noises, no sign of poor or lumpy running and idle is as quiet as this engine ever is & the indicated idle speed looks rock steady & bang on 900 rpm.

So in the immediate term, with the greatly apprecaited help of Lummox, Shark_90, Cheezemonkhai, WW_VRS and Decron, it looks like I may have gotten away with it unless there is anything else that I should be looking for, given my limited knowledge of diesels?

OK, Lummox, now all we need to do is have a chat about that "maybe MAF" problem ...

Once more, thank you all very much indeed, I greatly appreciate the time and effort you've all taken ...

Hi, we got your message a bit late today sorry (we ve been very busy), if you want us (unit18) to give your car a look at, feel free to pm me or Ross (lummox) or email [email protected] and we ll get you booked in

Ally

:: Unit 18 Automotive :: coming soon... ::

Glad to hear you've not done any immediate damage.

As said I'd probably get a fuel additive in there just to provide a bit of extra lubrication to the fuel system as the petrol will have had a cutting effect.

This one is pretty good and used by a fair few people on here with good effect as is forte fuel treatment. It should be noted skoda say no additives, but then I doubt they approve petrol either in a TDI

MILLERS OILS - A World Leader in Lubrication Technology

Glad to hear it's up and running! I must admit I'd probably be looking to move it on sooner rather than later but that's just me

Major pessimist! The most sensitive way of measuring whether any serious wear has happened during your little episode is to check out the emissions. The emissions profile will be badly affected if there's any appreciable wear to the nozzles. So if the emissions are within spec for the car's mileage you're okay.

The injector nozzles are the most delicate part of the system. The idea that you might have perpetrated some kind of non-nozzle damage that won't show up till later is pretty well zero.

I was under the impression the damage that is normally caused by petrol in a diesel is damage to the injection system as under normal operation conditions it is lubricated by the diesel

But on a PD car with unit injectors, as they are driven off the cam shaft, they are lubricated by engine oil instead of fuel so thus petrol tends not to cause the huge amount of damage it would in a common rail diesel

I may well be mistaken, misinformed or only know half the story