mis fuel

[dobie]

Hi, say hello to a dumbnuts, guess who just mis-fuelled his car????

I do not know what i was thinking about or why i checked when filling, but i ended up putting 7 litres of unleaded into a half full tank. i had to continue my journey so i brimmed the tank with diesel and then did a 200 mile journey and brimmed the tank again. during the trip the car never showed any signs of lack of performance or even missing a beat. i am now changing the fuel filter just to hopefully stop any dirt from the tank, but i do not know what else to check or how, any advice would be welcome and name calling is totally acceptable...

dobie

[rotodiesel]

7 litres of petrol to a tank of diesel is no real problem, although the VP44 pump is rather fragile.

Use a branded German made fuel filter and prime it properly, making sure you clean all dirt from the outlet connection. Mann & Hummel or Bosch are the best brands I tested when I was in the fuel systems business. VAG OE filters are now largely Chinese and should be avoided.

rotodiesel.

[dobie]

Thanks for the info rotodiesel, is the vp44 pump common for the superb engines or is it different for the v6 2.5 tdi which mine is?

[rotodiesel]

The V6 is the only engine to use this pump. The other diesels fitted to the Mk 1 Superb are PD engines which use unit injectors (combined pump and injector, one per cylinder).

rotodiesel.

[p1tud]

Ive put 15quids worth of unleaded in my superb, drove it till it spluttered to a halt then freewheled to a garage and brimmed it with diesel and have had no probs whatsoever, that was at least 10k miles ago.

[rotodiesel]

But that was a PD. I don't think a VP44 would thank you for that - it would be dead within 3 months.

rotodiesel.

[CRC]

Use a branded German made fuel filter and prime it properly

Haven't changed a fuel filter yet. Please could you tell me the the best way to prime it when the new one's just been fitted. Thanks

[rotodiesel]

I use a vac pump on the filter outlet to prime a replacement. A 1 litre Wanner oil gun used in reverse will do the job perfectly with one pull of the plunger.

It's also possible to use the in-tank lift pump to prime the filter, but it only runs for about 1 second after switch-on unless the engine sees a speed signal. This means you have to operate the key repeatedly to fill a new filter by this method.

Whatever method you choose, try to prime the system fully (mean old VAG don't provide a manual primer pump) so the VP44 does not see any air. With my PD, after using the vac pump, the engine starts instantly and does not hesitate.

rotodiesel.

[p1tud]

Just re read my post, ment to say i put it in by mistake and didnt realise until the car spluttered to a halt, ive never changed the fuel filter since so its the same one and my car has ran faultless so for the original op i hope this settles your nerves.

[CRC]

Many thanks for that, roto.

Edited 23 February, 2011 by CRC

[Supurbia]

GSF stock the Mann filter's, I always use them myself and the old ones that come out of the car are normally made by Mann anyway, GSF = about a 40% reduction in cost as well.

[dobie]

well it has been over two weeks since i mis-fuelled my car and whether or not it is my imagination but it seems to be running better than it ever has. i have had a problem with emmissions service and tracked it down to the egr valve, tried cleaning it out and the car responded with slightly better performance and no more light, but now it goes like a rocket sled so maybe i have been lucky and i will continue top monitor the performance for a while longer.

[dieselV6]

Around this time of year, all diesels start running better, because the fuel gets better with hotter weather.

Diesel fuel calorific content ("bang for buck") goes down towards/in winter and up towards/in summer. Prices go up all the time :wonder: .

At Arctic end of temp range, people (and companies) deliberately mix diesel with petrol (or even methanol/propanol) to prevent gelling. Put simply, diesel in winter is thinned out, how much thinned depends on how harsh the winter is in your area.

If you misfuel, main concern is loss of lubricity (that kills your pump), but since most/all diesel sold at forecourts comes now with 1%-5% biodiesel content (added at refinery/depot), this is largely a moot point until about 20% misfuel. If there are 2 things biodiesel is good at, it is lubricity increase (1% biodiesel into ULSD increases lubricity by ~60%) and cetane number increase (numbers vary, but it is good canceller of petrol contamination).

10%-15% petrol into old school diesel such as your (and mine) 2.5TDI does little harm as long as it is not repeated on a daily basis. Yes the VP44 is more fragile than others, but compared to any "new" diesels (PD or CR) it is rock solid. Just ask any French/Ford diesel user about their experiences...

Keep in mind that at the time when people complained about fragility of VP44 (10 years ago!), the comparison was often to indirect-injection diesels which were largely bomb-proof (and sluggish and often difficult to start), and to the VP37 which is also hard to break.