[Mk2 ] Putting diesel in a Mk2's tank

[Sidewinder]

Not me - my mate Matt accidently put BP diesel in his Mk2 N/A tonight by accident. The sign on the pump says 'Ultimate' in fairly large letters, with a tiny 'Diesel' in the corner, thus he didn't see the 'Diesel' bit and filled the tank thinking it was unleaded.

Anyways...he started the car, and the engine ran for a few minutes before a loud bang and plumes of black smoke coming out of the exhaust. The engine died, and it (natually) wouldn't restart.

Has any permanent damage been done to the engine here?

[BrianUK]

I have done exactly the same! I was in a motorway service station on the M5 at the time, wasn't in the AA and not too much cash on me....

Anyway after an hour of trying to siphon out the fuel I gave up and spent an hour looking for the fuel tank.

Having worked out it was in the center of the car I lay on my back, removed the plastic covers and found the tank drain plug..

Lucky for me a 3/8" drive fits the drain plug, so back into the garage to buy 3 petrol cans. I cut one open to make myself a drain pan and proceeded to empty the tank 5 litres at a time! Dont ask me where the diesel went

Anyway, having got out the diesel, I put a gallon of BP Ultimate PETROL in it and it started up no problem and has run sweet enough ever since!

I allways look twice now when filling up at BP!

[Sooty]

My mate who is a diesel fitter says ....

"probably not, drain it and flush out the diesel and put petrol in and see what happens"

[Sidewinder]

Brilliant - many thanks Brian and Sooty - I'll pass the info on.

Cheers!

[Goto10]

Also change fuel filter/plugs, they'll be gummed up now.

Aside from that and a flush you should get away with it ok, the other way around (petrol in a diesel engine) is certain engine death.

[DaMonsta]

Hi:

If you can drain the system and refill with fuel then you should have no problems.

Regards,
Jim

[System-G]

the other way around (petrol in a diesel engine) is certain engine death.

Not quite right...

A little petrol in a diesel engine is just about OK as long as the mixture isn't too severe. One of our subcontractors has done this twice
On one ocasion, he made it all the way to Birmingham (from Hemel Hemstead) before the engine died.
I have also heard of people putting a little petrol in the tank before MOT's in a bid to reduce exhaust smoke.

Diesel in a petrol engine is the bad one. Deisel is more dense and will do more damage. Don't even turn the engine over before draining.

At the end of the day neither engine is designed to run on the wrong fuel and any amount of damage can be done so it's best not to do anything until it's all been flushed out.

It may be an idea to change the fuel filter in a couple of weeks and get some injector cleaner in there then???

[Rogue]

Lucky for me a 3/8" drive fits the drain plug!

NOTE - The drain plug isn't there on all MR2s, I think they removed it at revision 3, although it may also be absent on late revision 2 cars.

I too once made this mistake in my first MR2 many years ago - also at a BP service station!

Rogue

[Bender Unit]

I have done exactly the same! I was in a motorway service station on the M5 at the time, wasn't in the AA and not too much cash on me....

Anyway after an hour of trying to siphon out the fuel I gave up and spent an hour looking for the fuel tank.

Having worked out it was in the center of the car I lay on my back, removed the plastic covers and found the tank drain plug..

Lucky for me a 3/8" drive fits the drain plug, so back into the garage to buy 3 petrol cans. I cut one open to make myself a drain pan and proceeded to empty the tank 5 litres at a time! Dont ask me where the diesel went

Anyway, having got out the diesel, I put a gallon of BP Ultimate PETROL in it and it started up no problem and has run sweet enough ever since!

I allways look twice now when filling up at BP!

Wow Brian, were you the secret member of the A team or somthing. I bet you could fashion a armoured car out of a biscuit tin and a packet of crisps.

Where is the drain plug on the fuel tank, I dropped the tank a while back to fit a bigger pump and never noticed one. - ah dont answer that just read Rogues post.

Cheers

James

[Dave Goodhand]

Diesel in a petrol engine is the bad one. Deisel is more dense and will do more damage. Don't even turn the engine over before draining.

Why is this? My understanding was that diesel doesn't burn with the compression or spark of a petrol engine. So in theory the car won't run at all.. it'll stall and won't be able to make an explosion. So shouldn't damage anything.

Petrol in a diesel however where the compression is high and they have glow plugs can ignite the petrol causing a massive release in energy and promptly a piston or con rod out of the block.

This was my understanding from logic anyway.

[anna]

As far as i'm aware, it's not only the combustion process that does the damage when putting the wrong fuel in.
It's the fact that the seals and stuff in the engine will get perished with the wrong fuel.
Can't remember which way round is worse.... i think it's petrol in a diesel engine...

If there is diesel in a petrol engine, then the combustion efficiency will be pap (as Dave points out), letting a whole load of unburnt fuel go into the exhaust system, which may then actually combust in the cat (if it's hot enough)...

Best thing would have been to not turn it over at all and drain it.....

[Mike R]

But isnt the diesal pump bigger than the petrol 'hole' to stop you putting it in the first place??

[Sooty]

But isnt the diesal pump bigger than the petrol 'hole' to stop you putting it in the first place??

Yes - its saved me a couple of times when getting similar looking BP pumps.

[BrianUK]

In short - No! lol! - it still fits in an MR2 filler... The AA have since told me that the most common call out they get concerning fuel problems is people mistaking BP Ultimate Diesel with BP Ultimate Petrol....


Brian

[Goto10]

Yeah petrol in a diesel car does other damage too, e.g. IIRC diesel fuel pumps rely on the diesel itself as a lubricant (very oily) - petrol kills them (from what I've read)
In my mind diesel not exploding in a petrol engine would've caused hydraulic lock (bad), but apparently not the case. I've also read that seals can perish when in contact with a fuel they're not intended for.
Another point is that petrol is designed to be resistant to self combustion (RON) whereas diesel works by self combusting under heat and pressure, so 2 very different fuels, although I've also read that petrol (in a diesel engine) starts igniting before the piston has reach TDC, eg working against it - conrod-bendy style (which seem to go against the logic of self-combusting-resistance)
From some scouting around on the web it appears the worst way around is petrol in a diesel engine for damage purposes. Not to say diesel in a petrol engine won't do any damage but the odds are lessened.

[turbomartin]

Read something in the paper the other day about petrol in diesel cars. Apparently this is a much worse problem because modern diesels prime the engine as soon as you open the door (so that the engine starts quicker) - you don't even have to try to start the engine to cause problems!

[ldavies83]

Not as bad in petrol engines, in fact it actually lubricates the engine . One of my bosses wives did this to her new corsa, spent a couple of weeks in a garage, clearing everything out, but all turned out well. Drain, new Filter/plugs, refill and injector cleaner! Jobs a goodun'

[Sidewinder]

An update on this one, as my mate has just got his car back from the garage.

Cost of draining the diesel from the tank was £70, but somewhere along the line, the alarm system (standard Toyota one) got messed up between the two key fobs, and prevented the car from starting. Very weird - fuel pump was running, spark was being produced, etc, etc, etc, but engine refused to fire.

So the cost breakdown was:

£70 to have the tank drained
£70 for a vehicle electrician to sort the alarm/ignition out
£40 worth of diesel wasted
£40 to refill the tank with petrol
£12 for a tow rope

...which totals £232 for one simple mistake!

[ioa1980]

SNAP!!!

Went to Taunton from North Wales a few weeks ago.

Went to a BP garage on M5.

Stopped at 'Ultimate' pump.

Started filling.

..then realised it was diesel!

I had put in about £4.50's worth. I then Filled the tank with Unleaded and drove off.

The turbo wasn't getting full boost and the engine was sluggish (as expected!!!)

After using as much fuel as I dare, I filled with super-unleaded and put in a whole bottle of STP injector cleaner.

The engine is now running as good as it was before.

The key with my experience was that i had an almost empty tank to start and only put in a little diesel, then diluting with petrol.

Its interesting to note that after the car had been standing for over 45mins, the diesel settled to the bottom and the car hardly moved (again as expected!) but as the fue was mixed due to driving it got better...smart! (well I thought!)

[Chietfain]

Did exactly the same as that,car was empty and put in £6 of diesel realised my stupid mistake and put in £20 of petrol.Apart from the black cloud following me it ran fine after that.BP should sort the ultimate pumps its an easy mistake to make