I recently purchased a 1974 PL620 truck, and on the way home the oil light came on.With the motor off I checked the dipstick, there was a small line of oil at the bottom end of the dip stick. So I gave it one quart, and did not notice a change on the dip stick. I then added another quart, still no change on the dipstick just a small bit of oil at the very bottom of the stick. I turned the motor on and checked the stick, this time the oil was above the H (high mark)I turned the motor off and checked the stick again, and it still was reading below the L (low mark)

I have owned a lot of vehicles and usually check the oil with the motor off. This is the first Datsun I've owned and wanted to know I should be checking the oil with the motor on.

no. always check it witht he motor OFF. that way you get an accurate reading. your just way low on oil. it takes about 4.5 quarts to fill an L16. if adding another quart or two doesn't solve the oil light issue, CHECK THE PRESSURE of the oil system. if the pressure is good then its a bad sender. if not, a KA oil pump, from what i have heard, is a good upgrade.