Any benefit of adding a few litres of petrol to diesel tank?

Skuxx · 03-09-2013 10:58am #1

I drive a mk4 golf (1.9 tdi) and got 5 litres of petrol yesterday as I was doing a bit of cleaning, removing tar from the paint work and I removed the egr and soaked it in a bit of petrol for a while to clean the gunk off, anyway I've about 2 litres left. I remember hearing lads saying a couple of litres into the diesel tank will help clean the injectors, is there any actual benefit to adding it in or is it all a myth?

jimgoose · 03-09-2013 11:08am

For the love of Mike don't go putting petrol into the diesel tank. If you want an injector cleaner get Redex Diesel blend or, better again, BG244K.

biko · 03-09-2013 11:08am

www.car-techie.com/oil.php?018

corkgsxr · 03-09-2013 12:28pm

It lowers the power of the diesel and can ruin your fuel pump

Max Power1 · 03-09-2013 12:30pm

I used to throw in 2-4 liters of petrol once every few months (into the tank) to clean it through, in a mk4 golf TDI. I wouldnt do it with anything newer mind.

4 liters on a full tank of diesel wouldnt have a bad affect, quite the opposite tbh.

Sobanek · 03-09-2013 12:55pm

I remember petrol being used during winter to make diesel a bit more fluidy

dgt · 03-09-2013 12:56pm

If you do so don't forget the 2 stroke

derry · 03-09-2013 2:04pm

If you really want to add things to diesel fuel that will help the fuel burn the best solutions are to add Hydrogen gas , Natural gas and other fuels like dymethal ether,some alcohols fuels and sometimes heavy diesel fuels like green diesel, some bio diesels and sometimes some kerosene fuels to name but a few .

In the case of adding natural gas there is no spark plug to ignite the fuel so it requires a mix of fuels typically 50% gas and 50% diesel fuel to make the engine work but some diesel engines can operate with 80% natural gas 20% diesel fuel.
In ROI with natural gas at 80 cents a liter its interesting for reducing costs.
Cost saving of more than ~20% seem possible .
Natural gas and hydrogen gas burn very cleanly and will even help to remove soots and carbons accumulations that have accumulated on the engine and exhaust and CAT's and PDF.

Adding Hydrogen is done using power from the alternator to crack water into hydrogen and oxygen. Because the flame front of hydrogen fuel is very rapid it helps burn up the bigger complex diesel Kerosene mix that is road Diesel fuels in Ireland .
So even though the energy put into making hydrogen is greater than the energy got back from burning the Hydrogen fuel because it amplify's the power of the diesel fuel it can make a net gain in some diesel engine set ups .
So far the best i have seen in HHO hydrogen fuel additives I have seen is ~55% extra MPG with petrol driven cars .

Natural gas ,Hydrogen fuels heavy and light Diesel fuels , dymetal ether, some alcohols, all share one quality they require high compression of more than 16:1 to operate properly .

Other fuels like Petrol and some alcohols work best with lower compression ratios often lower than diesel engines typically 16:1
However mixing these fuels with other fuels with high compression requirement can bring the fuels up to higher compression ratios to burn in diesel engines (burning doesn't mean functioning well)

In the 1970 cars with lead added petrol fuel were 12.5:1 and burnt only petrol.
In the 1980s the fuel was changed to 5% ethanol alcohol and 95% petrol.

Pure petrol ( is probably several percent diesel kerosene fuels mixed in the petrols ) with no lead or no alcohol added requires a engine with ~7:1 compression ratio and has very low power

A pure alcohol engine would require compression ratio of ~22:1 to work well

Toluene a additive used in petrol often is ~20% of petrol fuel but can be used in as much as ~95% toluene no petrol and 5% alcohols levels to replace petrol completely To use toluene correctly requires a engine with ~16:1 compression ratio to function but low compression engines can use it

As most modern petrol is mix of 20% toluene, 5% alcohol, and 75% petrol's the engine that burns this best is the modern ~10.5:1 compression ratio engine .

Racing cars with high compression engine of 16:1 with racing fuel are burning a high toluene content fuel.

Compression ratio for petrol engines is using OCTANE as the fuel marker the higher the octane the more reluctant to burn in the engine and the slower is the flame front of the fuel in the engine and the more chance the fuel will exist engine burning having not all been burnt up .The cat will then burn up the unburnt fuel (which means your burning up fuel in your tail pipe and not getting power from that fuel)
Adding Hydrogen to that fuel will mean more fuel will be burnt up in the engine as the combined flame front will be faster

Compression ratio for diesel is 16:1 and uses CETANE levels typically 55 for ROI . This the number that tells where the fuel will explode from compression
Petrol will have a bad cetane level so will not explode from compression levels alone.It will explode in a Diesel fuel mix as the diesel will ignite foirst and then set fire to the petrols fuel

The adding of Petrol to road diesel will result in the flame front being marginally faster in the engine .However where hydrogen is very fast flame front as it is simple molecule the petrol's are complex molecules and require more time to burn up and give up their fuel content the hydrogen within the fuel .
Some small amounts of petrol might in some diesel engines help the burning up the bigger more complex diesel fuel molecules.
However petrol burns at higher temperatures which the engine might not be able to get rid off this extra heat .
If the petrol comes in with injectors the fuel pumps might suffer from lack of lubrication and wear out fuel pumps faster .

However for various reasons diesel fuel contains some kerosene in it
Kerosene is really 1 part petrol and 7 parts paraffin
To stop light road diesel fuel from freezing in winter they often add more kerosene to road diesel fuel
Many modern diesel engines are made to serve many functions eg they can be static generators and marine engines and car engine all which use fuels which are often Kerosene fuels or light road diesel fuel or off road heavy diesel fuels .

Engine manufacturers tend to try to make the engines to work with all fuels from 100% kerosene through to light road diesel through to heavy off road diesel fuel without having to add on too many extra parts to cope with different fuels .

Some older engine in cars from the pre 1990 era non common rail will happily run on any of these fuels .I know one 1990 era Toyota Carina that ran for 200,000 miles using only kerosene fuel.I know one UK diesel car driver who for decades has run his cars on red diesel (the UK version of green diesel ) the heavy off road diesel fuels .

Best as I can figure modern road light diesel fuels are a mix of kersone fuels ,Then Light diesel fuels are the majority of the fuel with some heavy off road diesel fuels in the mix and nowadays ~7% bio diesel fuels .

In many parts of the third world the road diesels are nearly 100% kerosene fuels .
The motor manufactures have made the car engines to be tolerant of the huge differences in the fuel in the whole of the world .

There is one diesel fuel replacement dymetal ether that one day will probably replace all diesel fuels .Its the stuff they use in hospital called ether to knock out patients for doing surgery operations .It can be made from natural gas .It burn cleanly and there is no conversion requirements needed for engine ( might require mod to fuel pumps ) just fill tank with Dymethal either and drive away.However until it is made in mass production to bring downs its present high price its still too expensive to use in road Diesel cars. Small amounts of either added to diesel fuel looks like it give better MPG similar to effect of Hydrogen or natural gas fuels added to diesel fuel mix

So in conclusion I would suspect small amounts of petrol fuel added to Irish diesel fueled cars will probably have no real effect if not done too frequently .However the benefits are probably negligible if any and kerosene added is more likely to be beneficial .Mixing in some heavy off road green diesel with some small amounts of petrol will probably make a fuel that resembles the light rad use diesel fuels and probably give no benefits .
Users of heavy diesel fuels like green or red diesel fuels get more MPG from that fuel as it has more energy content in the fuel but its high sulfur content wrecks diesel fuel emission Particle filters

Derry

power pants · 03-09-2013 2:34pm

great post derry,very informative.

corkgsxr · 03-09-2013 3:02pm

power pants wrote: »

great post derry,very informative.

I tried to read it but my mind shut down half way

Matt Simis · 03-09-2013 3:11pm

corkgsxr wrote: »

I tried to read it but my mind shut down half way

Question asked was about dumping 2litres of petrol in Diesel, answer given was an assessment of Natural Gas, Hydrogen then an essay on Kerosene and a future analysis on the potential benefits of "Dymethal".

However for various reasons diesel fuel contains some kerosene in it
Kerosene is really 1 part petrol and 7 parts paraffin
To stop light road diesel fuel from freezing in winter they often add more kerosene to road diesel fuel
Many modern diesel engines are made to serve many functions eg they can be static generators and marine engines and car engine all which use fuels which are often Kerosene fuels or light road diesel fuel or off road heavy diesel fuels .

Engine manufacturers tend to try to make the engines to work with all fuels from 100% kerosene through to light road diesel through to heavy off road diesel fuel without having to add on too many extra parts to cope with different fuels .

Some older engine in cars from the pre 1990 era non common rail will happily run on any of these fuels .I know one 1990 era Toyota Carina that ran for 200,000 miles using only kerosene fuel.I know one UK diesel car driver who for decades has run his cars on red diesel (the UK version of green diesel ) the heavy off road diesel fuels .

Best as I can figure modern road light diesel fuels are a mix of kersone fuels ,Then Light diesel fuels are the majority of the fuel with some heavy off road diesel fuels in the mix and nowadays ~7% bio diesel fuels .

In many parts of the third world the road diesels are nearly 100% kerosene fuels .
The motor manufactures have made the car engines to be tolerant of the huge differences in the fuel in the whole of the world .

There is one diesel fuel replacement dymetal ether that one day will probably replace all diesel fuels .Its the stuff they use in hospital called ether to knock out patients for doing surgery operations .It can be made from natural gas .It burn cleanly and there is no conversion requirements needed for engine ( might require mod to fuel pumps ) just fill tank with Dymethal either and drive away.However until it is made in mass production to bring downs its present high price its still too expensive to use in road Diesel cars. Small amounts of either added to diesel fuel looks like it give better MPG similar to effect of Hydrogen or natural gas fuels added to diesel fuel mix