Slick oil: Richard Wilson's 20:50 at the Saatchi Gallery

Richard Wilson's engine oil-based art work 20:50 Photograph: Nils Jorgensen/guardian.co.uk Richard Wilson's art installation 20:50 Photograph: guardian.co.uk Richard Wilson's art installation 20:50 Photograph: guardian.co.uk oily reservoir Photograph: guardian.co.uk A visitor peers into the oily reservoir Photograph: guardian.co.uk A visitor looks at 20:50, a reservoir containing 8,000 litres of recycled engine oil Photograph: Ben Stansall/guardian.co.uk