'Dirty petrol' - is it pretty much a red herring?

[Caveat]

I've noticed throughout the years that 'dirty petrol' is often offered as an excuse for poor running/starting etc and I'm really starting to wonder about this.

My current (good) mechanic of the last 3 years or so has never once suggested this as a cause of any problem yet previous mechanics who have turned out to be lazy/incompetent in other ways tended to come up with old dirty petrol suggestion at the drop of a hat.



I get the feeling that genuine dirty petrol is not nearly as widespread as some mechanics & wannabes would have us believe. I'm not saying it never happens, but surely there are only really two main causes of this:

• Quality control issues - e.g. some problem with the pump or some procedure not carried out prior to delivery etc - I'd assume these kind of problems are rare enough.
• Pumps in very isolated areas which are used very infrequently and where sediment may build up - not all that common either I would guess.

I really think that the majority of the time it's mechanics who couldn't be bothered diagnosing properly.

Is genuine 'dirty petrol' really that much of a problem?

I mean, what is the fuel filter for if not to help prevent this kind of thing anyway?

And more importantly - am I simply talking rubbish?

 

[Pique318]

To a large extent, no, you're not talking rubish but it DOES happen.
Petrol is not clean and there are gonna be contaminents in there from the tanker ship and then the truck and the underground tank at the station and finally the tank in your car. If the tank at the station is nearly empty then crud/sludge 'could' be sucked up and cause the fuel filter to become partially blocked. This will happen more in older cars as this crud/sludge accumulates over the years.
My car can run a little poorly if I'm 'running on empty' but I've never had the car conk out as a result of this.

Sensor failure and lack of oil changes, coolant changes, plug repacement and common or garden carbon build up in the throttle bodies are the most common causes of poor running/starting IMO.

 

[briancbyrne]

yea - def does happen - mothers new car got a dose of it from a nearby garage - apparently a few cars had been affected - ended up having to have work done on the engine. The garage initially refused liability but after a letter threatening legals they backed down and paid the garage bill