He wasn’t really concentrating this morning when filling up, and only noticed too late that he’d begun to fill his tank with unleaded, not diesel.

Anyway, when Ihe realised what he was doing, he stopped, swore, and had the bright idea of topping up the rest of the tank with diesel.

So, the tank now has about 20 litres of unleaded and 55 litres of diesel in it. MyHis plan is to keep topping it up with diesel and never letting it get to less than a quarter full for quite a long time, thinking that over time the unleaded will dilute into the diesel and eventually everything will be hunky-dory.

Is this a reasonable plan? Will Ihe, or more importantly myhis van, die?

FWIW, it’s a 1.9 turbo diesel T5.

you might get away with it.

key thing will probably be whether the petrol content stops the fuel pump being lubed properly.

I understand that this should be OK, as long as you keep topping it up regular like. I Someone I know once put a FULL tank of diesel in my their diesel Passat and had the great idea of trying o get it home. It just stopped, got towed to the garage and sorted.

FWIW your insurance generallt covers you for such mishaps.

Friends van? No problem, fill his boots (and tank with DERV).

Your van? Ahhhh…. Mebbies a more salutary approach is called for….

I’d refill with derv when more like 3/4 full rather than 1/4.

Not only will it explode, but the pollution coming from it is so toxic that every baby robin within a 100 miles will instantly die.

I did it in a transit connect a few years ago, I think topping it up completely every time the tank is a quarter down would be a better idea,as it is the pump that is starved of lube. In your favour is the fact that it is a big tank. Keep filling it up and you will get off with it.

You only need to pass this on if he is a close mate of course…. 8)

Head somewhere really cold as you now have extreme winter derv.
As above I’d top up at 3/4 full just to keep diluting it. Could get smokey out the back too.

I’d refill with derv when more like 3/4 full rather than 1/4.

Yeah, that is the plan, 1/4 would be the absolute bare minimum.

baby robin within a 100 miles will instantly die.

Meh, **** ’em 😉

There is a petrol/derv ratio that is supposed to be fine – I suspect you’re over it but I’d go with your plan (top up frequently).
I think the injectors are the other bits that require lubing by the diesel.

Meh, **** ’em

What if its a child’s face?

So how long should my friend stick to the ‘keep topping up at 3/4’s full’ regime?

What if its a child’s face?

You’ll have to take me at my word that I’d never fill a child’s face with unleaded.

So how long should my friend stick to the ‘keep topping up at 3/4’s full’ regime?

4 or 5 times? Would equal a full tank of diesel.

Sounds like a perfect opportunity for a spreadsheet and some charts plotting the concentrations. You’ll still end up with homoeopathic petrol though. My friend put almost a full tank of petrol in his diesel, he was an idiot and charts couldn’t help him.

5th gear did a test years ago:

Filled a petrol car with diesel and a diesel car with petrol.

The diesel engine with petrol worked fine, the petrol car didn’t.

STOP NOW!

Get the fuel drained.

It’s just not worth the potential grief on a modern diesel.

Theres two potential issues – one is the fuel pump being stripped of lube by the petrol, the other (with some engines) is any rubbers and plastics in the fuel line can sometimes be attacked by the petrol. So you want to avoid running the engine too rich a petrol mix for the former issue, but I’d also not want the petrol sitting around in the system for and extended period either so having topped up with as much diesel as poss already I’d probably do another two or three 1/4 or 1/3 tanks then try and run the tank to near empty so you can fill with fresh fuel and rather than having the petrol hanging around in reduced concentrations for weeks

My friend did this a few weeks ago. Brimmed an empty tank with unleaded. Dumbass.

He worked it out as he hung the nozzle back up, so didnt start the engine, but got it relayed home by the AA where he could arrange for someone with the necessary certificates to syphon the fuel out and put it in his 200 chainsaws, ahem.

Then went out with some cans to get some diesel and then fire it up. No problems, as petrol never entered the system.

Refilling after using a quarter of the tank

Refill Unleaded Diesel Total % unleaded
0 20.0 55.0 75 27%
1 15.0 60.0 75 20%
2 11.3 63.8 75 15%
3 8.4 66.6 75 11%
4 6.3 68.7 75 8%
5 4.7 70.3 75 6%
6 3.6 71.4 75 5%
7 2.7 72.3 75 4%
8 2.0 73.0 75 3%
9 1.5 73.5 75 2%
10 1.1 73.9 75 2%
11 0.8 74.2 75 1%
12 0.6 74.4 75 1%
13 0.5 74.5 75 1%
14 0.4 74.6 75 0%

Refilling after using three quarters of the tank

Refill Unleaded Diesel Total % unleaded
0 20.0 55.0 75 27%
1 5.0 70.0 75 7%
2 1.3 73.8 75 2%
3 0.3 74.7 75 0%

Your mate sounds like a right ****t. – Hope you laughed at him, whilst trying not to spit coffee over the keyboard.

Is what £100 of diesel really worth the risk ? I’lld get it drained. Tell your mate he’s OK to tip the mixture straight down the drain, providing he washes it down with some washing up liquid. 😉

On the basis of the spreadsheets, if you’ve already started driving it I’d go for the second option (maccruiskeen’s).

But on the basis of Wikipedia

For some diesel motors it is also possible to add even lighter fuels like gasoline to extend the CFPP characteristics. Some car makers were recommending adding up to 20% gasoline to permit operation in cold weather (at the price of higher consumption) and it had been common practice in Europe where No.1 fuel is not offered at gas stations. Since the 1990s car makers began selling only direct injection diesel engines – these will not withstand any gasoline portions in the fuel as the high pressure in the injection device will ignite the gasoline early on possibly destroying the injectors.

I’d get it drained

Interesting, get the pain out of the way then? By mileage it’s around 2100 miles v 1350, based on 600 miles-ish per tank
…the diesel molecules will still have the memory of petrol though 🙂

Edit: oh.

it will be fine, i did the same in an old diesel audi i have a few months back, stopped and topped it up with diesel and it was fine, as long as he had some diesel in it will be fine and then top up with diesel as he uses the unleaded.

My dad did this once with his Skoda Octavia (1.9TD, same engine’s as the OP’s (mate’s) van), except he brimmed it with unleaded a day before he was due to tow his caravan back from Penrith area to Burnley.

Not knowing how better to proceed he drove home towing the caravan!! He said that it was all OK at first but was gradually losing power the closer to home he got, but he made it.

My mate picked the car up the following day, took it to his garage, completely drained and flushed the fuel system, filled it with diesel, repressurised it, started it and hey presto! never had a problem since. And that was two years ago.

So I suspect with a 75/25 mix your mate should be OK…

I’d have it drained at over a 1/4 petrol. Modern diesels are expensive to repair. Drain and clean will cost you about £150 a diesel pump at least £1500

park up, remove filler cap and start a small fire under the fuel tank – petrol will preferentially evaporate and viola!, risk-free diesel motoring 😀

Finally, a sensible suggestion 🙂

Would you not be better linking your mate to this thread,save you having to monitor it for him and then relay the information back to you?

I did it in my old Connect. Filled right up with petrol and then went. Drove it on the motorway and it got a bit sluggish on the slip road, then i remembered i wasn’t in the car and had just filled with petrol. Then it just stopped.

Had it drained the next morning, new filters plus 20 litres of diesel to flush the lines out all for £150.

End result to make life easier was we got a diesel car too so i don’t have to remember if its green or black.

I’d keep it topped up all the time for a couple of weeks. If i’d realised when i was filling up, thats what i’d of done.

Oh, he’s keeping an eye on it, don’t worry. I’m just here out of concern for him.

Well, my friend rang the local garage where he gets it serviced and they reckon my friend should just keep it topped up.

In fact, they said, had they done the same as my friend and started filling with unleaded, they’d have done exactly what my friend did.

Mmmm . . .

Sounds like a Garage that knows sweet FA about modern diesels.

Point is you can often get away with it and if you have no intention of keeping the vehicle for any length of time it may not be an issue. However those unit injectors on VW’s PD engines are around £300 each.

Go figure – as they say

Hth

Your local garage is probably hoping you’ll take the van to them for the engine rebuild.

Are they happy to drop their advice on an email ? – Thought not.

You see, now he’s worried again.

A mobile call out to drain the tank’s going to cost him £150+ (it’s that or a 40 mile drive to the garage, which may charge him less, but would mean running the engine on the dodgy mix), plus the £100 of fuel, so that’s at least £250 to get it drained.

That’s against what likelihood of it actually causing a problem, given that there seems to be a lot of anecdotal evidence of others doing it with no ill-effect?

EDIT – for what it’s worth, I’ve used the garage for years and trust that they’re not trying to screw me.

FWIW, it’s a 1.9 turbo diesel T5.

Right. How old? If it’s not common-rail, which I think is unlikely unless it’s pretty new, you’ll be fine I think. Check the user manual, see what it says.

I’d defriend. You don’t need idiots like that as mates.

I thought diesel was heavier than petrol. If this is true, will it not sink to the bottom and then be pulled through the pump leaving the unleaded at the top?

Could you not syphon the lot into a paddling pool, light the petrol to burn it off leaving the diesel behind which you then pour back in?
Simples

Its a shame you didnt spend a bit more time messing with old cars, instead of attending school (in particular A level maths) when you were younger. – You could have have helped him out by a doing it yourself and saved a few quid.