CORE A 4W6039 - Caterpillar

The most accurate check of the engine oil level is obtained when the engine is stopped.
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(1) Filler cap
(2) Engine oil level gauge
Remove filler cap (1) to ensure that the crankcase pressure is equal to the atmospheric pressure.Excess pressure or a slight vacuum will affect engine oil level that is measured.
Ensure that engine oil level gauge (2) is seated.
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(3) "ENGINE STOPPED WITH OIL COLD" side
(4) "ENGINE AT LOW IDLE WITH WARM OIL" side
(5) "ADD" mark
(6) "FULL" mark
If the engine is stopped, remove the engine oil level gauge. Observe the engine oil level on "ENGINE STOPPED WITH OIL COLD" side (3).
If the engine is operating, reduce the engine speed to low idle. Remove the engine oil level gauge and observe the engine oil level on "ENGINE AT LOW IDLE WITH WARM OIL" side (4).The engine oil level should be between "ADD" mark (5) and "FULL" mark (6).
Engine damage can occur if the crankcase is filled above the "FULL" mark on the oil level gauge (dipstick).An overfull crankcase can cause the crankshaft to dip into the oil. This will reduce the power that is developed and also force air bubbles into the oil. These bubbles (foam) can cause the following problems: reduction of the oil's ability to lubricate, reduction of oil pressure, inadequate cooling, oil blowing out of the crankcase breathers and excessive oil consumption.Excessive oil consumption will cause deposits to form on the pistons and in the combustion chamber. Deposits in the combustion chamber lead to the following problems: guttering of the valves, packing of carbon under the piston rings and wear of the cylinder liner.If the oil level is above the "FULL" mark on the oil level gauge, drain some of the oil immediately.
If necessary, add engine oil. For the correct engine oil to use, refer to this Operation and Maintenance Manual, "Refill Capacities and Fluid Recommendations". Do not fill the crankcase above the "FULL" mark on the engine oil level gauge. Clean the filler cap (1). Install the filler cap.
Record the amount of engine oil that is added. For the next engine oil sample and analysis, include the total amount of engine oil that has been added since the previous oil change. This procedure will help to provide the most accurate analysis.