prepare 8-10%(w/v)bentonite suspension in distilled water,by stirring with a lab stirrer (5000-6000 rpm) for 30 minutes and ageing at 90C for 48 Hrs. add 4% (w/v) sodium chloride (LR grade) and age for 24 Hrs.at 25C,adjust the apparent viscosity of this suspension to 15-16 CP by dilution with 4% Sodium Chloride solution. then add 0.5% (w/v) of the product, stir with hamilton beach mixer for 15 minutes at high speed. measure lubricity coefficient by lubricity tester