i do the same .
a bit of petrol doesnt hurt i do the same i my landrover,my wife and daughter have bothe put petrol in derv cars then phoned me panicking luckily they only put a couple gal in or£20 i just told them to fill the tank up both cars have been ok thats is last year cars are ok one was a vw and other was merc e270 but i would not advise a customer to do that.i work in a garage and lots of people do it.nigelboh:I put 2 gallon in an 80litr tank about twice a year. it helps clean up emissions and as a cleaning effect on the injectors. its cheaper tha some of the diesel cleaners on the market.
Not ideal for running on neat. If you do accidently fill up with petrol .push to one side drain tank and slap your wrists .Best not drive on it. Could be costly.
I would keep what you drained out and use it slowly over the next few months abit at a time.