[New shoot]

You can check whether the soil is fertile by scattering green manure over it - you would dig it in in the spring anyway, but if you get bald patches that could mean pools of contaminated soil.

If you want to do a test first over the whole area I would mass up some old jam jars and systematically work over the plot putting small soil samples in each, then add water.  Oil or petrol will make a slick on the top and if it's all over, then you are looking at digging it all out and replacing the top soil.

[Swing Swang]

Right newshoot:

http://www.ehow.com/how_5936441_test-petroleum-soil.html

SS

[Axe]

well i have been a busy bee...i done the water tests, one every square metre of earth (some more concentrated at certain area's) and there is a big patch of fuel/oil in the centre and at the very top aswell (and a couple of 1 foot patches).

so i have come to the conclusion the patch in the centre is where the cars were parked and the oil was flowing) i done some digging down and found some empty oil containers...so i assume this was the back of the garage which he kindly dumped all his old oil and other motor fluid 

so on the good side i just have to replace about 3 square metres, rather than the entire garden side.

[JayG]

Glad to hear that Axe (although of course you could have hired an oil rig and made yourself a few million!) 

[New shoot]

That sounds like a result Axe 

[Axe]

yup..it has cheered me up..and also been offered a half share of a 30x30 allotment, so in a months i have went from a 2 bed flat with a yard, to a 3 bedroom house huge oil field and half an allotment,...might just lawn out the oil field and use the allotment for veggies.