12.34.2(d) . vacuum gauges; 

not an engine instrument. The vacuum gauge uses a Boudon tube to measure the amount of vacuum (suction) less than atmospheric pressure which is produced by the vacuum pump in order to drive vacuum powered instruments.

12.34.2(c) . direct reading oil pressure gauges; 

– a thin tube takes oil from after the oil pump to the instrument. A Boudon tube is used to provide the indication on the instrument.

12.34.2(b) . manifold pressure and boost gauges; 

12.34.2(a) . tachometers (rpm) gauges (centrifugal and drag cup); 

12.34.2. Describe the function and principle of operation of the following instruments:

12.32. Lubrication Systems - Engines

12.32.16. Describe the correct oil replenishment procedure for a typical aircraft.Instruments 

Use the dipstick to establish the quantity required.
Take care to ensure that any filler funnels used are clean.
Use the correct grade of oil.
Clean up any oil spilled during the process.

12.32.14(e) . high oil temperature. 

Monitor oil pressure
Open cowl flaps (if fitted)
If high temperature persists land as soon as possible. Particularly if pressure starts to decrease.

12.32.14(d) . low oil temperature; 

Check cowl flaps if fitted. If closing cowl flaps does not raise temp then land as soon as possible.

12.32.14(c) . fluctuating oil pressure;