Save my boss from himself - Petrol in diesel

-Mike- · 10 Jun 2014 at 21:42

Hey all,

Can you just advise me whether it's a smart idea for my boss to be driving his car when he's just put £30 of petrol in it. He filled it right up with diesel but surely damage will be caused to fuel pump and injectors with that mix?

Thanks

mjt · 10 Jun 2014 at 21:43

Don't start it. Get it towed and have the tank drained.

£30 worth must be half a tank at the least??

-Mike- · 10 Jun 2014 at 21:45

It was 22 litres of petrol, topped up with 31l of diesel. May have had 10l left in the tank before hand!

Hyburnate · 10 Jun 2014 at 21:47

He's drove a diesel car with petrol in?

-Mike- · 10 Jun 2014 at 21:53

Hyburnate said:
He's drove a diesel car with petrol in?

Yes.... apparently no funny noises yet. I figured he'd be best to drain it.

acemastr · 10 Jun 2014 at 21:58

Diesel fuel pumps are really expensive!

Hyburnate · 10 Jun 2014 at 22:00

-Mike- said:
Yes.... apparently no funny noises yet. I figured he'd be best to drain it.

And he's the boss of someone, get it towed to your local reputable garage and hope it isn't screwed.

( |-| |2 ][ $ · 10 Jun 2014 at 22:29

I've known people do the same thing in a E39 & E60 530d.
No issues reported 1000's of miles later.

Not that I'd recommend it at all.

Mercenary Keyboard Warrior · 10 Jun 2014 at 22:41

Used to dilute diesel with 25% (max) petrol in winter so its unlikely to massively implode

keep topping up and diluting as frequently as possible

Diagro · 10 Jun 2014 at 23:07

Sifen it out... not hard to do.
Then use the fuel in a crappy old van lol

G-Man · 11 Jun 2014 at 00:15

AFAIK If its a modern common rail style thing then epic bills are quite possible but if its old school mechanical pump based it'll probably be perfectly fine.

OpenToSuggestions · 11 Jun 2014 at 00:31

The diesel will sink to the bottom of the tank as it is more dense, so he probably won't have damaged it as the diesel and petrol would split out evenly if sat still, just like water and cooking oil would.
I would not bother with an expensive tank drain, but I would let the car stand for an hour before syphoning off the fuel at the top of the tank.
Then I would top it up with diesel every 100 miles for a few thousand miles.

A friend put petrol in his 1.9tdi Golf. It would not start, but once diesel was in it then there was no problem. This was an old non-commonrail diesel though that loved to create smoke.
I would think modern diesel fuel pumps and injectors would poo themselves.

I have two cars. One petrol. One diesel. Before pressing the trigger I always look at the colour of the filler hose, then look back at the car and say out loud which fuel I need.

JRS · 11 Jun 2014 at 00:47

OpenToSuggestions said:
The diesel will sink to the bottom of the tank as it is more dense

As far as I know, petrol and diesel are completely miscible so what you're suggesting won't happen unfortunately.

-Mike- · 11 Jun 2014 at 01:18

G-Man said:
AFAIK If its a modern common rail style thing then epic bills are quite possible but if its old school mechanical pump based it'll probably be perfectly fine.

He drove it home anyway... I give up! It's got half a tank of diesel v power and half a tank of petrol v power... she'll be like a rocket ship

Threepwood · 11 Jun 2014 at 01:37

Petrol in diesel? Most likely fine at that ratio. As mentioned 25% petrol to diesel to stop it freezing in sub zero environment is not uncommon.

If it were the other way around (diesel in petrol), different story.

Rich1988 · 11 Jun 2014 at 01:51

Threepwood said:
Petrol in diesel? Most likely fine at that ratio. As mentioned 25% petrol to diesel to stop it freezing in sub zero environment is not uncommon.

If it were the other way around (diesel in petrol), different story.

I was under the impression that petrol in diesel was actually much worse than diesel in a petrol? due to the laquering/ruining of the CRD injectors?

Orionaut · 11 Jun 2014 at 08:28

G-Man said:
AFAIK If its a modern common rail style thing then epic bills are quite possible but if its old school mechanical pump based it'll probably be perfectly fine.

This

In my Old diesel. User manuals actually recommends 25% petrol in extreme cold conditions.

CR involves much higher pressures and much closer tolerances so the lubrication properties of the fuel are of greater importance.

Another eason why old is better perhaps??

(In an ideal world everybody is perfect and never makes mistakes. In the real world they are not and they do! "Real World" technology should be reasonably user-error tolerant! If it is not then perhaps it is not really fit for purpose! :/ )

jfp · 11 Jun 2014 at 08:43

So I was under the impression that you couldn't put diesel into a petrol due to nosel shape and the size of the filler hole or something to that nature

As to petrol in a diesel engine, quite a few petrol stations have a guide that says what to do depending on how much petrol you have put in... so like if you put x petrol in and top it up with x diesel it should be fine etc etc

When my dad put petrol in his diesel motor (must have been mostly petrol in that tank) it drove for 20 meters then stopped (and also made a god awful noise whilst it was driving)

OhEsEcks · 11 Jun 2014 at 08:49

Topping up your petrol car with 50% diesel increases torque output by 25%. Everybody knows that.

snapdragon69 · 11 Jun 2014 at 10:14

The answer depends on what type of engine and fuel system it is.

If it has a high pressure pump (common rail) get it drained, these pumps are already running at the minimum level of lubrication required and adding petrol drastically reduces the lubricity of the fuel.

If it's an older and non-CR car, I'd just add a litre of 2 stroke oil and top off with diesel - if you don't really care, you could also do this on a common rail engine and take a gamble..

What year/car /engine is it?