glowplug said:

Diesel is an oil, petrol is an alcohol/solvent. A diesel pump relies on the oil based nature of diesel to lubricate the working parts. Petrol cleans away the oil from the moving parts making them run metal to metal and the net result is failure. In actual fact oil does not lubricate it separates. As it resists compression two surfaces with oil in between experience an hydraulic effect called the hydraulic wedge. If it weren't for the reliance on this lubrication diesel engines would run on petrol (albeit not great) so I am sorry but the comments about seals failing are inaccurate. Maybe if immersed for a long time in petrol the rubber seals might start to degrade but it would not happen in the period of a misfuel. As other have correctly stated topping up with diesel is the best approach and 2 stroke can't hurt either. Even a small amount of 5w-30 will help if need be.

Diesel engines run VERY happily on engine oil as has been experienced by anyone who has suffered runaway due to a blown turbo seal or because of failed DPF regens causing an overflow of the sump.

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This is a very confusing post. First define oil and solvent? Most oils are solvents and both petrol and diesel are oils. The modes of lubrication in a high pressure, highly loaded system are complex and rely on more than just an oil film. Additives are important. The removal of most of the sulphur from fuels for environmental reasons caused issues for some aircraft and diesel engine fuel systems. Sulphur compounds re surface modifiers, remember the smell of older EP gearbox oils? Thats sulpur and phosphorus. Adding lubricating oil to the fuel does not help lubricate modern fuel systems and can cause gumming and carbon buildup. Stick to products intended for the application.

Robert G8RPI.

Since you obviously like to put petrol in your tank it might be time to buy a car that runs on it rather than devil fuel?

Maggers, that is not a bad suggestion cos I believe it's not as bad if I put diesel into a petrol car, or...

Update: I've sloshed some Millers into the tank and I'm already getting 46 MPH ! Only done about 10 miles!

Car still starting and running OK touch wood. Haven't run over any black cats yet, but I had to stop for a very slow hedgehog (that's why they get run over, never heard this discussed on "Springwatch" - amateurs!)

If the car goes bang, the story will continue on the Ford Focus forum... £875 for an '06 reg hmmmm...

but if it's on the Focus forum we won't know......! Seriously, which i don't often do, I had a diesel Multi a few years back and it was fine. I just get fed up with having to glove up every time i fill a diesel - mild allergy to diesel - so i'm petrol all the way now. i don't do a huge mileage but i accept it's a concern for others who do.

g8rpi said:

Hi,
Don't worry too much about this. last year I put petrol in my 1.9 16V mJTD Croma. No excuse but it was foul weather, away from home, different brand (black pump handle), and the wife went in and paid so I missed that last chance to catch it and get it drained. It turned out to be a near perfect 50/50 mix, I didn't notice and drove over 200 fairly hard miles without stopping. Only thing was a slightly "lumpy" engine on over-run and slow re-start after a food stop (parked on steep hill) did another 100 miles on motorway pulled into services and checked last receipt

.
Brimmed it with quality diesel and drove (more gently) the remaining 100 miles home. Brimmed and added Millers for the next 3 3/4 levels in tank. then ran down to less than a 1/4 and brimmed for a final dilution. I've had no adverse affects. I also changed the fuel filter just in case it had been affected.
The de-fuel specialists and recovery companies will now tell you that just turning the ignition on will damage the pump (AA seemed to change their advice a couple of years ago and now offer a drain and flush service at extra cost). but clearly this is not the case for the mJTD (or JTD). I'd say up to 25% petrol in an older car, just brim it with diesel and don't flog it for a tank or two.


Robert G8RPI.

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I was about to mention this..

g8rpi said:

Brimmed and added Millers for the next 3 3/4 levels in tank. then ran down to less than a 1/4 and brimmed for a final dilution.

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Update: Am following this plan from g8rpi. Second top-up from 3/4 tank today plus Millers. Car running OK. If this works I've saved myself £157 = Cost of fuel drain (£100) + full tank of fuel (£70) - Millers additive (£13). Suppose I shouldn't count my chickens/savings yet...

:spam: PS. To celebrate progress so far I've pushed the boat out and treated myself to some Spam tonite. Wonder what I should do with the other £155.50 I've saved?

MarkX said:

Wonder what I should do with the other £155.50 I've saved?

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Lots more Spam!

g8rpi said:

This is a very confusing post. First define oil and solvent? Most oils are solvents and both petrol and diesel are oils. The modes of lubrication in a high pressure, highly loaded system are complex and rely on more than just an oil film. Additives are important. The removal of most of the sulphur from fuels for environmental reasons caused issues for some aircraft and diesel engine fuel systems. Sulphur compounds re surface modifiers, remember the smell of older EP gearbox oils? Thats sulpur and phosphorus. Adding lubricating oil to the fuel does not help lubricate modern fuel systems and can cause gumming and carbon buildup. Stick to products intended for the application.

Robert G8RPI.

Click to expand...

Really !!!!!! I suppose it is only confusing because you are trying to be deliberately pedantic. I believe anyone with the ability to read into the message that petrol is going to strip out the necessary lubrication from the pump would not have found it overly confusing. Clearly this was lost on you so here please take a read, taking particular note of the second sentence of the first paragraph. I would suggest the good Dr that wrote this article knows significantly more than you and I on the subject.

https://www.greenflag.com/breakdown-cover/misfuelling/what-happens

glowplug said:

Really !!!!!! I suppose it is only confusing because you are trying to be deliberately pedantic. I believe anyone with the ability to read into the message that petrol is going to strip out the necessary lubrication from the pump would not have found it overly confusing. Clearly this was lost on you so here please take a read, taking particular note of the second sentence of the first paragraph. I would suggest the good Dr that wrote this article knows significantly more than you and I on the subject.

https://www.greenflag.com/breakdown-cover/misfuelling/what-happens

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I stand by what I said earlier and add that petrol is not an alcohol. I've read the link you posted and consider it over simplified and biased it's presented in conjunction with a de-fuel and clean service for people who have mis-fuelled. Specific issues are "perhaps costing less than £100" when refering to a fuel filter. A typical filter is £5-6 and an expensive one is £20. The comments on fuel lines and seals "Petrol can eat away at some seals in a diesel engine so it needs to be flushed through with a cleaning agent" are also wrong. Components in some fuels can affect some seals, most common is swelling and softening, some will harden. Once a seal is damaged a "cleaning agent" can't repair it. Again, the clearances in modern diesel componens are too small for conventional oil film (hydrodynamic) lubrication. The pumps and injectors rely on extreme pressure lubrication. See http://www.brighthubengineering.com/manufacturing-technology/73568-hydrostatic-lubrication/
I looked up the "good Dr" (Dr Geraint Owen) and he does not seem to be a fuel, lubrication or diesel specialist. Most of his work appears to be related to manufacturing and production lines http://www.bath.ac.uk/mech-eng/people/owen/index.html
I'm not a Dr (my wife is but knows noting about engines or fuel systems) but I am a Chartered Engineer. Lubrication is not my speciality either (Electronics aircraft and radio) but I know more than the average person and I'm not trying to sell mis-fuel drain and clean service. The AA used to say couple of litres of petrol in a full tank of diesel was not an issue before they had a drain service (not covered by your membership) now they say even the smallest amount is an issue. This may also be due to the increase in common rail systems but the cynic in me (and direct experience says otherwise)

Robert G8RPI (CEng MRAeS)

The article is obviously set out to be simple for everyone, and to promote their service. However, much of what is said is true, if perhaps a little over pessimistic. A good idea to frighten the general public, to prevent real damage from happening.

Older diesels used a high pressure injection pump, with very tight tolerances, to create the pressure at the right moment to cause injection to occur. These will not like the loss of lubrication if petrol is passed through them.
Modern common rail diesels just have a high pressure pump, much simpler, and the injectors are operated electrically, like a petrol injection. They are likely to tolerate petrol a little better.

One thing that is not mentioned is the volatility of petrol. When petrol is ignited by a spark in a petrol engine, it does not explode, but burns very rapidly. If it explodes, when we hear the 'pinking' noises, it causes shock waves that can hammer the top of the piston, jamming the top rings, and eventually pop a hole into a piston. Diesel fuel ignites when injected due to the heat in the cylinder and like petrol, burns rapidly. Petrol injected into a diesel explodes, and can hole pistons, although takes a little longer due to the extra strength of the components.

Whichever system is used, diluting the fuel as early as possible is often all that is needed.

portland_bill said:

<SNIP>


Older diesels used a high pressure injection pump, with very tight tolerances, to create the pressure at the right moment to cause injection to occur. These will not like the loss of lubrication if petrol is passed through them.
Modern common rail diesels just have a high pressure pump, much simpler, and the injectors are operated electrically, like a petrol injection. They are likely to tolerate petrol a little better.

SNIP>.

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Hi Bill,
This is not quite correct. Modern direct injection (common rail and similar) diesel systems use much higher fuel pressures, over 1000 bar (15,000 PSI, 3000 bar (45,000 PSI) is not unknown. Older indirect injection systems used 100bbar or less. Direct injection systems were tolerant of petrol (my old Astra owners manual used to recommend up to 20% petrol in winter), modern direct injection systems are the ones that don't like it.


Robert G8RPI.

Update: Haven't noticed any problems, and I seem to be getting better fuel consumption with the Millers Diesel Power Ecomax - regularly seeing over 50mpg recently, compared to previously around 37-ish in Winter, and 40-45 in Summer.

Potential savings using additive:

fuel consumption (w/out additive) = 40 mpg (say)
fuel consumption (with additive) = 45 mpg (say)

Current diesel price: £1.15/L @ 3/9/2017
1 gallon = 4.5L
Additive cost (per litre fuel) = £14.00 /500ml (where 1ml additive per litre fuel)
= £0.028/L

Price/mile (without additive) = £1.15 * 4.5 / 40 mpg (say)
= £0.129/mile
= 12.9p/mile

Price/mile (with additive) = (diesel price per liter + additive price per litre fuel) * 4.5 / 45 mpg (say)
= (£1.15 + £0.028) * 4.5 / 45 mpg
= £0.118/mile
= 11.8p/mile

Saving using additive = 12.9 - 11.8p/mile
= 1.1p/mile
=======

(At 50mpg the saving becomes 2.3p/mile)

Plus the other benefits of additive to fuel system.

Quite possible the petrol acted like a detergent and has done a bit of cleaning itself. Although not a recommended action of course.