530 Farm Mechanics. 



tance and should receive the most careful attention. It 

 requires a special lubricating oil for gasoline engines and 

 only this oil should be used. It is known on the market 

 as gas or gasoline engine oil. All parts should be care- 

 fully wiped clean at frequent intervals to free them from 

 grit or gummy products and the operator should always 

 have an ear to the sounds of his engine and should know 

 what are normal and what are not in order that he may 

 the quicker discover when anything is getting out of order 

 and remedy it in time. 



665. Gasoline, Only the best quality of gasoline should 

 be used with these engines, that known as the "74 test 

 gasoline." 



666. Size of Engine In purchasing a motor of any kind 

 it should be remembered that it is much better to get one 

 which has a little greater capacity than will be needed 

 than one which is a little too small ; and this caution ap- 

 plies with special force to the gasoline engines, for the rea- 

 son that their capacity cannot be increased above the nor- 

 mal. With the steam engine it is possible to increase the 

 steam pressure and the rate of firing, and the horse may 

 for a short time develop two, three or even four horse- 

 power, but if you overload a gasoline engine it must stop. 

 If, therefore, it is desired to use steadily two full horse- 

 power from a gasoline engine it should be not less than a 

 three horse actual to do at all times perfectly satisfactory 

 work. 



It should be said in this connection, however, that it is 

 never economical of fuel to use a large engine to develop a 

 small horse-power. A 10 H. P. engine could not be eco- 

 nomically used when it is desired to simply pump water 

 from an ordinary well or to run a small separator which a 

 man can turn. There should be a rational relation be- 

 tween the engine and the amount of work it is expected 

 to perform. 



