Petrol in diesel engine - fuel consumption way up!

RandR

Hi,
My wife put unleaded into a diesel engine :mad: (05, Seat Alhambra) and drove until it conked out. She got it drained at side of the road and refilled with some diesel and drove on and thought that was the end of that.
but I've noticed over the last few weeks that it's doing way less mileage than it used to - it's down by about 20-30%.
Any suggestions as to what might be wrong and how much it could cost.
Thanks.

jimgoose

How far did she drive it? That is, how much petrol would she have put through it? The unfortunate position is modern-ish turbodiesels have sophisticated, delicate and expensive fuel systems that depend on the lubricity of diesel fuel. There could be a fair bit of damage in there, to pumps, injectors, etc.

dr.fuzzenstein

How do you measure fuel consumption?
When I had some fuel system trouble, the computer was miles off for quite a while.
If it's onboard computer, reset and measure again, but also measure by actual consumption by mileage, i.e. fill tank till it clicks off, at next fill record mileage and fill till it clicks off again. From that calculate consumption.
Personally I record km driven and liters filled.
Divide km driven by 100 and then divide liters filled by that number:
923 km and 60 liters:
923/100=9.23
60/9.23=6.5 l/100 km.
Someone else will be along shortly to show you how to do MPG, but I find calculating imperial from metric an unnecessary and redundant step (puts on asbestos trousers)
Don't brim the tank as some people will tell you, because you could flood the carbon filter. Modern fuel tanks are NOT meant to be brimmed to the top of the filler neck.


edit:

If you want to know MPG:
282 divided by your l/100 km figure:
282/6.5=43.38 MPG for the above example.

cruizer101

dr.fuzzenstein wrote: »

fill tank till it clicks off, at next fill record mileage and fill till it clicks off again. .....
Don't brim the tank as some people will tell you, because you could flood the carbon filter. Modern fuel tanks are NOT meant to be brimmed to the top of the filler neck.

Is that not the same thing, I always though when people said brim the tank the meant til the nozzle clicks off. Would some people actually take the nozzle out and fill it til it is literally ready to overflow.

On topic, even doing this now is slightly moot unless already have records from before the issue. Could compare with what other people in same car get, honestjohn realmpg stats

dr.fuzzenstein

cruizer101 wrote: »

Is that not the same thing, I always though when people said brim the tank the meant til the nozzle clicks off. Would some people actually take the nozzle out and fill it til it is literally ready to overflow.

On topic, even doing this now is slightly moot unless already have records from before the issue. Could compare with what other people in same car get, honestjohn realmpg stats

I'm just making sure.
If you don't have records from before, how do you know your fuel consumption is up?
But apart from that, yes, it would be best to find out what the mpg on your car should be and then compare it to what you're getting.
I checked the Honest John real life MPG for my car (06 CMax, 1.8 TDCI 115 hp) and it is spot on.

RandR

She drove about 1km before it cut out.

mickdw

Is it showing any signs of damage? Driving poorly, smoking?

RandR

mickdw wrote: »

Is it showing any signs of damage? Driving poorly, smoking?

No smoking, no odd noises and driving as usual but fuel consumption is way up.

dr.fuzzenstein

RandR wrote: »

No smoking, no odd noises and driving as usual but fuel consumption is way up.

OK, but how do you know it's up?

RandR

dr.fuzzenstein wrote: »

OK, but how do you know it's up?

Hi,
Before the incident it was doing about 620 to the tank, this is now down to 430 for a full tank.
I knew how much mileage it did to the tank beforehand and then filled up post incident and compared mileages.
Thanks for interest.

dr.fuzzenstein

I'd say get it plugged in and see if any error codes show up.

toyotaavensis

How many tanks have you gone through since she put in the wrong fuel?
If it is just one or two I wouldnt worry yet.

Stavros Murphy

You did change the filters first chance you got, right?

Mech1

Whoever drained the system may have caused a leak.

ironclaw

One tank isn't a good average. I'd be putting at least three or four full tanks though it. Probably no harm to put some system cleaner through it as well. If your still having trouble at that stage I'd get it checked. That said, a third less mileage is pretty extreme. I presume your quoting actual range (i.e. Fuel light) and not the trip computer range?

dr.fuzzenstein

My own mechanic swears by hydraulic oil in the tank, 500 ml on an empty tank and fill up with diesel. This will clean out your system.

dr.fuzzenstein

Also, OP, please be aware when the tank was drained that all fuel in the system was drained, this would have been a few liters, throwing fuel economy readings and also actual range way off.