Your oil fired Aga range cooker has a high and low fire oil flow rate. The cooker senses heat loss, via the thermostat, and moves the oil flow to high fire rate until the target temperature is reached.
High & low fire oil flow rates for Aga range cookers...
Low fire rate = 4cc per minute (1 cc = 1 millilitre)
High fire rate = 8cc per minute (1 cc = 1 millilitre)
You can adjust the flow rate via the screws on top of your oil control valve. Turn the screws max 1/8th of a turn before checking the flow. Clockwise reduces the flow and anti clockwise increases it.
Note... low flow rates are almost always due to blockages; altering the screws is your last resort!