Accidental petrol in diesel

[Tatsfield]

I need reassurance. I accidentally put 1.88 litres of unleaded petrol into the tank of my 2012 XC70. Since it was a small amount, I decided to brim the tank with diesel to dilute the petrol to the minimum. I reckon that filled the to very brim of the filler pipe the tank holds about 70 litres and the petrol represents about 2% or 3% contamination at the worst. I read that the industry recognised 7.5% as the safe limit of contamination. Have I got away with disaster with under half the safety limit?

It still amazes me that the fuel nozzle diameters prevent you putting diesel into a petrol tank, which isn't totally disastrous but doesn't stop you putting petrol into a diesel tank which is. Who thought of that bright idea!

If it isn't a disaster, I intend to use a quarter of a tank and refill it and do this a couple of times to reduce the amount of contaminant in the tank the only way I can.

[yostumpy]

I regularly ued to put 2ltrs of petrol in my diesel landrover, but this was to dilute the cooking oil, when I got caught out with an overnight change of weather, to wake up to thick frost. Had no effect whatso ever. but that wasn't a common rail , highly complex, electronically controlled engine. I would have thought you would be fine mechanically, possibly if it runs hotter ...maybe a sensor might throw something up? Can't really help, sorry. But having miss fuelled,, and then filling up , you have a) diluted the fuel, b) incurred additional expense of the diesel should you decide to drain. Personally , I'd do as you suggest, just keep topping up, every time you do ,it lessens the chance of a problem. Maybe throw in one of those lubricant/cetane booster jobbies, to make sure?

[Moomoo]

Originally Posted by Tatsfield

I need reassurance. I accidentally put 1.88 litres of unleaded petrol into the tank of my 2012 XC70. Since it was a small amount, I decided to brim the tank with diesel to dilute the petrol to the minimum. I reckon that filled the to very brim of the filler pipe the tank holds about 70 litres and the petrol represents about 2% or 3% contamination at the worst. I read that the industry recognised 7.5% as the safe limit of contamination. Have I got away with disaster with under half the safety limit?

It still amazes me that the fuel nozzle diameters prevent you putting diesel into a petrol tank, which isn't totally disastrous but doesn't stop you putting petrol into a diesel tank which is. Who thought of that bright idea!

If it isn't a disaster, I intend to use a quarter of a tank and refill it and do this a couple of times to reduce the amount of contaminant in the tank the only way I can.

I did something similar,(worse)’in my 1.6v70 , no consequences. All was fine.

[monkeh]

May be a bit difficult in common rail diesels to dilute the petrol as all the high pressure pumps are precision units. But maybe chuck a large shot of 2 stroke oil to circumvent the degreasing properties of petrol if you want. Use synthetic marine/low ash to avoid dpf issues. I chuck 100ml per tank in mine anyway, it may be placebo but it seems to run quieter.

Petrol in diesel appeared to be the norm in the d24tic engine, it even says in the owners manual to use a certain percentage of petrol in the diesel in cold climates!

[Tannaton]

ANY Diesel engine will run fine on the occasional dose of 10% petrol/diesel mix, maybe even 20%. For many years owners of older diesel vehicles used to do that ever 4 - 5 tankfuls (black cabs etc).

Contrary to what you might think, common rail diesels are less susceptible to it than older direct injection engines as the fuel system is mechanically much more simple (but electronically more complex…)

You will be fine…..

[Olaf Els]

Originally Posted by Tannaton

ANY Diesel engine will run fine on the occasional dose of 10% petrol/diesel mix, maybe even 20%.

Could I ask how you know that "will run fine on the occasional dose of 10% petrol/diesel mix, maybe even 20%"? It's a higher figure than is normally quoted. I'd be interested in what hard evidence you have.
Thank you.

[Tatsfield]

The generally quoted figure is 7.5%. Perhaps there is a margin of caution holding the percentage down and it might not be catastrophic to exceed it by a small amount. However since my personal foolishness only amounts to 3% at the worst, I'm felling better about it and hope that I will not come to regret that 2 seconds of inattentiveness. I don't suppose anyone feels that its worth doing anything to help prevent this sort of accident as the growing trend towards electric cars will eliminate it. Perhaps they are now worrying about filling your Tesla with the wrong sort of electricity!

[Tannaton]

Originally Posted by Olaf Els

Could I ask how you know that "will run fine on the occasional dose of 10% petrol/diesel mix, maybe even 20%"? It's a higher figure than is normally quoted. I'd be interested in what hard evidence you have.
Thank you.

You can (and should) ask - but I'll answer carefully as not to come across the wrong way...

A 35 year career in several forms of engineering, starting with environmental (air con) and other avionic systems in military aircraft but more significantly 12 years in the motor trade, culminating in 3 years in Aftersales Management for a small motor group with 5 franchises across 8 sites.

Whilst I was privy to the varying procedures that each manufacturer would stipulate for mis-fuelling incidents, there were in fact two processes - customer making and insurance claim and car in warranty versus customer out of warranty and paying cash. In the latter case I've seen hundreds of cars towed in, fuel system drained, new filter, maybe a new sensor if there is a sacrificial mis-fuel detection sensor, 25 litres of fresh diesel and off they go, and never come back.

Whilst Jaguar/Land Rover & Volvo stipulate virtually the entire fuel system is replaced following a mis-fuel & start, Toyota & Nissan would (at that time) just require the fuel filter and a few sensors replacing if the car ran as it should otherwise - and at the time they were offering the longer warranties.

So I appreciate what I say on the matter would be more "sanguine" that other advice out there, but I'm entirely confident about it based on my experience.

The process of replacing all the fuel system following a mis-fuel, especially on older cars at the customer expense (£7k on a D5 for example) is nearly as big a money spinner as topping up headlight fluid.

[Olaf Els]

Originally Posted by Tannaton

... I appreciate what I say on the matter would be more "sanguine" that other advice out there, but I'm entirely confident about it based on my experience.

Thank you for sharing your experience and the basis for your views on this subject. A fascinating insight! Much appreciated.

[Tannaton]

Originally Posted by Olaf Els

Thank you for sharing your experience and the basis for your views on this subject. A fascinating insight! Much appreciated.

I do apologise - in my full head of steam to substantiate my views I didn't actually answer the specific question....

If we got a call from a customer who had partially filled a diesel car with petrol - after ascertaining the percentage, if it was less than 20% we would advise them to fill up again at 3/4 tank, then repeat 3 times, and drive gently. But no need to have parts replaced, drain etc.


I would add that most of our dealerships were small towns and just a few in cities so we operated more as a local garage than a franchise.