Long before Drake, in 1859, demonstrated that oil could be obtained by sinking wells, primitive man found it necessary to lubricate the axles of his carts and wagons to reduce friction and diminish wear. Lubricant taken from the axle of a chariot in a tomb sealed in about 1400 BC was analyzed and found to be beef or mutton tallow or a product of similar characteristics suitable for use in a warm climate. The first steam engines were lubricated with tallow, castor oil, and lard oil. While such animal and vegetable oils served their purpose in the primitive machine, they would be impractical in the engines of today, largely because of their inability to withstand the high temperatures involved. Oil in the crankcase of a heavy duty engine will reach one hundred and fifty degrees centigrade and the temperature at the upper piston ring grooves may exceed two hundred and fifty degrees centigrade. These high temperatures and the large quantities of air pulled through the crankcase ventilator make conditions especially favorable for oxidizing the oil which increases its viscosity, forms and precipitates sludge, and develops acidity. Fortunately chemical inhibitors have been found, small traces of which can be added to oils to reduce their susceptibility to oxidation.