Supposing I was to hypothetically put a couple of litres of unleaded into the wife’s diesel car, and then topped it up with diesel to “dilute” it, would I be able to hypothetically get away with it?

It would hypothetically be about 2 litres amongst 58 lires of diesel.

The car seemed to – hypothetically – run alright on the way home after this hypothetical incident, but could there be a hypothetical problem if the fuels seperated out while it is parked overnight?

I would – obviously – be very hypothetically stupid to have hypothetically done such a thing……. 😳

It’ll be fine with that much dilution, and no it won’t seperate out.

On a modern deisel, it may reduce the life of certain components, but not to the extent I’d be worrying about it.

😆

That cheered me up…and not hypothetically

i suspect it’ll be fine. it’s a lot worse (though less likely to happen) the other way round.

better to drain the entire tank but i have done this [ ex wife not me] on an old non HDI diesel and it ran rubbish but nothing bad happened

Iirc it ruins seals and it will dependent on the pump seals and other stuff tbh.
if it does break it will be fubbarred and new engine time

here some proper stuff for you
If you’ve added less than 5 litres of petrol – Top up with diesel and run normally unless the manufacturer has advised otherwise

Ha Ha!
I hypothetically filled my Passat up with unleaded before Xmas, cost me the tank of fuel plus £180 to drain it. Luckily I didn’t start the engine (I’m not THAT stoopid!)

My ex-boss filled his Beemer with petrol, but since it was a company car he had it towed, drained and a load of work.

Next time I said, just call me and we’ll syphen the petrol into mine 🙂

I’m feeling – hypothetically – a bit easier having read that AA link…..

If you ever walk out of the kiosk and then suddenly realise what you’ve done…don’t unlock your car! Some cars start to prime the fuel system as soon as you unlock the car, before you even get in!

Ha Ha!
I hypothetically filled my Passat up with unleaded before Xmas, cost me the tank of fuel plus £180 to drain it. Luckily I didn’t start the engine (I’m not THAT stoopid!)

and didnt you used to be a pump jockey at the local fuel refilling station.

spooky_b329 – Member
If you ever walk out of the kiosk and then suddenly realise what you’ve done…don’t unlock your car! Some cars start to prime the fuel system as soon as you unlock the car, before you even get in!

What’s the plan there then, leave it on the forecourt as a lasting memory of your stupidity?

and didnt you used to be a pump jockey at the local fuel refilling station.
Ha! Nice of you to remember project. I actually owned the petrol station (not with Bombers though)
Gawd was I pi$$ed off with myself when I did that. 🙄

Errr…thats the recovery guys problem! Never done it, thankfully 🙂

unless you actually ran out of fuel there will still be fuel in the lines so i cannot see that being a problem tbh
All engines I am aware of [ possibly out of date knowledge as iam not a grease monkey] use a pump driven by the engine for obvious reasons – more revs more fuel. I cant see how why they would “prime” tbh electrically.
Some self prime meaning you dont have to do it by hand when you change tanks or run out of fuel etc but that is a different issue and still requires the engine being turned over

I would not be overly concerned about that issue tbh

The would drain the lines and the pump which they would probably do anyway just in case and flush it all with diesel i assume

Working on company vehicles, I’ve drained and seen lots of petrol being drained from diesel vehicles, and I’ve only ever seen one that resulted in damage (idiot filled a transit with petrol, but rather than getting it recovered after it started running rough, he kept driving it until the tip burnt of the injector and melted a hole in the piston)
Most of them had been started, and only ended up being recovered after breaking down.

The manufacturers will tell you that the entire fuel system needs replaced, as seals, pump and injectors will fail, but I’ve yet to see any of those fail directly as a result of misfuelling.
It may reduce the life of certain components, but those certain components are likely to fail anyway, so the worst you’re doing is reducing there life.

Junkyard, lots of diesels have an electric low pressure pump, and on some vehicles it runs briefly as soon as the vehicle wakens up i.e. when you press unlock on the key fob/open a door.

why do they do this ? does the fuel drain back or something?
Surely the pump still has fuel in it and it is only the lines that will have drained??
Basically Why ta

mc’s correct, my Passat primes when you turn the ignition on. No idea why Junkyard.

The unlocking thing is an over-reaction, there are 2 ways to draw diesel into the fuel pump, either an electric lift pump in the tank, or a smaller transfer pump driven off the main fuel pump. The main fuel pump and transfer pumps are driven off the engine so aren’t a problem until you turn the key. Lift pumps are cheap compared to a whole common rail system.

As for fuel pumps in common rail systems, the cam and follower are separated by about 20 microns of diesel at 2000 bar when operating under full load, gasoline doesn’t have the lubricity necessary and won’t maintain a hydrodynamic layer. Metal on metal contact will lead to surface fatigue pretty quickly and injectors don’t work so well full of debris. A whole cr system will make a lot of cars a write-off pricewise, and people like me are employed to analyse failed parts returned under warranty – we can tell when there’s been lubricity breakdown rather than poor machining etc.

The amount of unleaded you can get away with depends on the lubricity of what it’s diluted with, in future if it was to hypothetically happen again I’d top up with something like vpower diesel not supermarket stuff if possible.

May have once theoretically put a couple of quids worth of petrol into one of the diesel galaxies on the pool fleet. This didn’t really happen obviously but if it did I’d have brimmed it with diesel and it would have run ok all be it a bit smokey and with the engine management light on until it was half full when I may have re brimmed it with diesel from which point it seemed to suffer no I’ll effects. Probably.

why do they do this ? does the fuel drain back or something?
Surely the pump still has fuel in it and it is only the lines that will have drained??
Basically Why ta

Couple of reasons, different on different cars. Because the injectors on a petrol car require the rail to be at pressure before they can fire a *known* quantity of fuel for startup. If the engine just fired up as the pump span up to speed the first few injections would be of some unknown quantity, or the ignition would have to be held off until pressure was raised.

On CR D’s the lift pump is needed to prime the main pump and ensure no air gets sucked through, it fires up to ensure there’s a decent head of fuel to feed the pump and the air has been expelled. Again, if it didn’t you’d have to wait a few rotations during cranking to get up to pressure and that means more battery drain and I guess it’s something a customer doesn’t want, they want to just jump in and go.

I have a 3 event pause on my ignition to ensure I get oil pressure up and the ensure the ECU gets a stable timing signal (light flywheel, cranking crank speed varies massively making ignition timing hard) and that seems like eternity in the morning despite really only being 0.6 seconds.

I’m a time served motor fitter & I’m thinking a lot of water’s gone under the bridge since I was on the tools!

I know (not from experience of course) that a Honda diesel engine ‘could’ take up to 50/50 petrol/diesel….according to the Honda techs. I don’t know what you are driving though, so not sure if it would apply to your motor?

Now how would I know what kind of car I might have been hypothetically driving? 🙄

*whispers* 55 reg Octavia 1.9 TDI. Just hypothetically, like.

Just keep topping it up with diesel to dilute it more at every chance you get. You may have to come clean to the wife though.

55 reg octy, most likely a Bosch PD type system rather than common rail, fair bit more tolerant fuel wise.

You are too late should have done it in the big freeze as anti freeze.

if I had an A6 2.7Tdi which already had 150k miles on it and had put a litre and a bit of petrol in it, I would probably just have stuck 60 litres of diesel in on top and not worried about it (much). And after another 5k miles or so I might not have noticed any ill effects. Probably.

a few people round here were putting a litre or 2 of petrol in their tanks to stop it freezing, when it was -20odd

i’d not worry too much.

no problem.

I put about 4 litres in my newish Passat with about 10 k miles on it at the time Topped up with diesel and the car is still going strong now with nearly 200k on it with no problems fuel related.