Petrol in a diesel car

[Anghammarad]

Went to fill up one of the cars today and managed to put 7,5 liters of petrol in it before I discovered my mistake. Proceeded to fill it up with 60+ liters of diesel. Googled a bit and found a lot of conflicting info. Some say it's an absolute catastrophe and some say it no problem at all. The car is a '06 VW Passat TDI. Anyone with real knowledge?

 

[Dragonistic]

I think the cut off is around 10% of the tanks volume being petrol in a diesel before you have real trouble. In other words, if you have a 75 litre fuel tank you should be ok if you brim the tank with diesel. If more then 10% of your tank is now petrol you may need to drain the tank (really you shouldn't have started it until you knew what to do).

Hopefully you have less then 10% in there and you should be good, but it won't hurt to keep topping it up with more diesel regularly rather then run the tank near empty.

 

[Scaff]

I think the cut off is around 10% of the tanks volume being petrol in a diesel before you have real trouble. In other words, if you have a 75 litre fuel tank you should be ok if you brim the tank with diesel. If more then 10% of your tank is now petrol you may need to drain the tank (really you shouldn't have started it until you knew what to do).

Hopefully you have less then 10% in there and you should be good, but it won't hurt to keep topping it up with more diesel regularly rather then run the tank near empty.

This 👍

A small amount of petrol in a diesel engine is not the end of the world. It will run a bit crappy for a while, and as Dragonistic says, keep topping up to dilute it.

Now had it been diesel in a petrol, that would be a totally different matter, that can end up being new engine time if you try and start it (which is why you may have found conflicting info as many people get the two situations the wrong way around).


Scaff

 

[Stotty]

Now had it been diesel in a petrol, that would be a totally different matter, that can end up being new engine time if you try and start it (which is why you may have found conflicting info as many people get the two situations the wrong way around).


Scaff

👍 Diesel in a petrol does all sorts of horrible things to the fuel pump and injectors.

 

[Jim Prower]

True. Diesel fuel is a much more basic, and thus thicker, distilate of Petroleum, or Crude Oil. In fact, early diesels and hot-bulb engines often ran on thick stuff like bunker C. Running Diesel in a petrol engine will cause problems...it's simply too thick. It may not look like it, but to a petrol engine, it's like molasses. Try starting an older diesel in temperatures of 10F or below.

On the other hand, petrol is far more volatile. However, doing the math...

(7.5/(7.5+60))*100= 11.111111111111111111%

So it should be safe so long as you keep the tank filled for the next week or so.

 

[Anghammarad]

It's a 70 liter tank so it's actually closer to 10%. I've read that it's more critical for a common rail engine but I'm not sure whether the engine is a common rail engine or not. It's the 140 HP 2.0 TDI. I think that they didn't start using common rail until 07 or 08

 

[Tornado]

I read the topic title wrong, and thought that Anghammarad just threw away his engine. When we bought our first RV it had already had the entire powertrain, including fuel lines and the second gas tank, replaced when we bought it because of a hilarious mix-up the previous owner had done when filling it up once.

 

[Duke]

👍 Diesel in a petrol does all sorts of horrible things to the fuel pump and injectors.

Not to mention the catalytic convertor. Our friend's stupid husband put a tank of diesel in her almost-new Honda CR-V. It barely made it home from the gas station, and when he got there, the convertor housing was hot enough to see the red glow under the car in the daylight. I was amazed it didn't catch on fire.

 

[Anghammarad]

Update. Managed to siphon 35 liters from the tank and fill up with diesel so that it is now around 5% petrol. Driven 100 km (extremely carefully). So far so good, everything runs just normal.

 

[Dragonistic]

Sounds like you're in the clear then, seeing as you'll be diluting the petrol more and more (as advised) each time you put more Diesel in the tank, the worst and more hazardous part is over.

 

[Pupik]

👍 Diesel in a petrol does all sorts of horrible things to the fuel pump and injectors.

It's a potential catalytic converter-killer too (if the car is started); sometimes not all at once, but eventually...and a sure-fire ego destroyer.

 

[Ibonibo]

Normally you fine, refuel a lot to dilluate it even more.

But still there is a lot worse, like putting an energy drink (nos) into your bike.

 

[TheCracker]

You should have just thrown a match into your fuel tank. Diesel isn't volatile enough at normal temperatures to ignite that way, so the petrol portion would have burnt off leaving you with just diesel in the tank. Simplez. 👍

 

[G.T]

You should have just thrown a match into your fuel tank. Diesel isn't volatile enough at normal temperatures to ignite that way, so the petrol portion would have burnt off leaving you with just diesel in the tank. Simplez. 👍

Fair plan!

 

[HPT]

👍 Diesel in a petrol does all sorts of horrible things to the fuel pump and injectors.

I'm not sure you can even fit a D pump in a P hole over here...

But yeah, it's really very bad mojo.

 

[Eric.]

Not to mention the catalytic convertor. Our friend's stupid husband put a tank of diesel in her almost-new Honda CR-V. It barely made it home from the gas station, and when he got there, the convertor housing was hot enough to see the red glow under the car in the daylight. I was amazed it didn't catch on fire.

I don't understand how you accidentally grab diesel fuel. Almost all the stations around here don't even have diesel on the same pump as gasoline. I'd understand it being common for people to accidentally put gas in a diesel vehicle here, particularly if its not their car (wife driving the husbands truck, friend with a friends VW TDI, that sort of thing).

 

[Kryz11]

Thats why you don't let friends drive a car unless they know cars as much as you do.

 

[BMW POWER]

Friend of mine did this about 3 weeks ago with his 09 Seat Freetrack 2.0TDI, but he filled the entire tank with it! Made it about 3 miles until it cut out. Called a local service that come out to you in a van, stick a pipe in your fuel tank and suck it all out. They stuck a 25L can of diesel in it and off she went, no problem what so ever (except the £200 they charged for the convenience ) So I'm sure you should be fine.

 

[daan]

I don't understand how you accidentally grab diesel fuel. Almost all the stations around here don't even have diesel on the same pump as gasoline.

Most pumps over here do.

This pump has diesel and 2 types of unleaded.

 

[Tornado]

I don't understand how you accidentally grab diesel fuel. Almost all the stations around here don't even have diesel on the same pump as gasoline.

Lots of gas pumps in rural areas (for example, Northeastern New York) have 87, 89 and diesel rather than 87, 89 and 91/92/93. Though somewhat more common is to have the normal islands, and then have a separate diesel island off to the side.

 

[Sniffs]

I can see where the goof comes from up tornado's way. most people look at the position of the handle rather than at the price, color, etc

Note that Daan's posted a pump shot clear enough to read the fuel grades! the gas is 95/99 pump grade respectively. see, I keep telling you guys europe runs a higher grade of fuels!

oh, keep an eye out of you get a yank tourist at those tescoes. some of our stations use green colours to indicate the diesel pump, and black for the basic grade of petrol. you might get a chuckle

 

[ExigeEvan]

I don't understand how you accidentally grab diesel fuel. Almost all the stations around here don't even have diesel on the same pump as gasoline. I'd understand it being common for people to accidentally put gas in a diesel vehicle here, particularly if its not their car (wife driving the husbands truck, friend with a friends VW TDI, that sort of thing).

Habit. Or driving a business car or a hire car and not checking what it requires. Which is why most fleet cars these days have a big obnoxious sticker on the fuel cap to tell you.

I can see where the goof comes from up tornado's way. most people look at the position of the handle rather than at the price, color, etc

Note that Daan's posted a pump shot clear enough to read the fuel grades! the gas is 95/99 pump grade respectively. see, I keep telling you guys europe runs a higher grade of fuels!

oh, keep an eye out of you get a yank tourist at those tescoes. some of our stations use green colours to indicate the diesel pump, and black for the basic grade of petrol. you might get a chuckle

We measure our octane slightly different to you guys.

 

[Stevisiov]

I don't understand how you accidentally grab diesel fuel. Almost all the stations around here don't even have diesel on the same pump as gasoline. I'd understand it being common for people to accidentally put gas in a diesel vehicle here, particularly if its not their car (wife driving the husbands truck, friend with a friends VW TDI, that sort of thing).

I think its most commonly done when someone spends most their life with say a petrol car, it becomes habitual to go to the petrol pump. Then when they get a new car/drive a friends car/drives a hire car, which runs on the other fuel type, people still go to the same pump they have been using all their life by mistake.

 

[Sniffs]

Exige: I think it's still a minimum of one or two octane numbers difference, even using our method.

 

[Famine]

Exige: I think it's still a minimum of one or two octane numbers difference, even using our method.

It's always four.

No US equivalent = Super-unleaded 98-100RON
Premium 93 octane = Super-unleaded 97 RON
Special 91 octane = Unleaded 95 RON
Regular 89 octane = No EU equivalent

 

[Sniffs]

uh, or regular is 87, not 89. and 91 premium over here is reserved for the likes of Mercedes, Jaguars, beamers, rollers, etc.

 

[Joey D]

uh, or regular is 87, not 89. and 91 premium over here is reserved for the likes of Mercedes, Jaguars, beamers, rollers, etc.

It depends on the state, here in Michigan premium is between 91-94 octane.

 

[Famine]

I've put fuel in a Mustang in two states so far, and both were 89/91/93 pumps.

Because US "octane" rating is the average of Motor Octane and Research Octane numbers ([MON+RON]/2), and Research Octane is typically 8pt higher, EU pumps have a number 4pt higher than US pumps for the same fuel. If you can find somewhere carrying 95 octane, that's the same as the 99RON pump daan photographed. The 95RON pump is the same as 91 octane on yours - the stuff I put into a Mustang in San Francisco, Bakersfield, Mojave and Las Vegas, and which I put into our E39 every week.

The US rating system is better. It tells you that the MON - more appropriate for real-world conditions - is a given value as well as the RON. 91 Octane has to be 95-96RON, 86-87MON. We only get told the RON - which is based on a bench test in unrealistic conditions (though there are further regulations governing the quality of fuel in the EU).

Is there a quality difference between US 91 octane and EU 95 RON? Possibly - different regulations may apply to the different territories but notionally they ought to burn the same because 91 octane is 95RON. Comparing 87/89 octane to 95RON isn't helpful because they aren't the same fuel but you should always fill up with the lowest octane rating that gives you zero knock - and the US has lower octane options than the EU.

 

[Omnis]

Ours here are 87/89/91. Could it be possible that these are only MON numbers? That would make sense since the grades are each 2 points lower.

Kind of off-topic chemistry question: does straight-chain octane even exist in gasolines, or does it just prefer to be 2,2,4-trimethylpentane?

 

[Famine]

Ours here are 87/89/91. Could it be possible that these are only MON numbers? That would make sense since the grades are each 2 points lower.

No - they'd need to be 4pt lower.

It could just be that there's little demand in your area for higher grades - and higher grades require more refining and are thus more expensive to produce. If people gas up their trucks with 87, the petrochem companies will keep supplying cheap 87 to you.

Kind of off-topic chemistry question: does straight-chain octane even exist in gasolines, or does it just prefer to be 2,2,4-trimethylpentane?

It's not necessary for anything given an octane number to contain any octanes - even iso-octane - at all. Octane rating is merely "under x conditions, burns with the equivalence of a mix of n percentage iso-octane/heptane mixture", the n being the rating. It's actually "burns without knock", which allows for higher than 100 ratings.

95RON fuel resists knock as much as a 95% iso-octane/5% heptane mix would, under RO conditions. 91 octane fuel resists knock as much as a 95% iso-octane/5% heptane mix would, under RO conditions and as much as an 87% iso-octane/13% heptane mix under MO conditions. 102RON is 2% better at resisting knock than a 100% iso-octane fuel, under RO conditions.