单项选择题 If the engine can be started and maneuvered on high viscosity fuel, the （）of the fuel reaching the injectors should be raised to such a point that the viscosity is less than the required value, ie27c St.

单项选择题 On engines having oil cooled pistons the lubricating oil pre-heater must be put into operation and the rate of heating so （） that the temperature of the piston cooling oil returns are 32℃ to 35℃ over a period of at least two hours.

单项选择题 Too much excess air is （）because the heat generated is being lost through the exhaust trunking instead of being made used of in heating the water to produce steam.