Again I agree with Bib.
However I know getting an oil test is popular in the US.I've never had one done but found these people,
http://www.theoillab.co.uk
http://www.theoillab.co.uk/product-c...esting/engine/
They have different price range tests so I wouldn't know which was best.If you are thinking of repairing the engine it might be worth getting one done.