Seriously its too low if the light comes on.... If you check the handbook it says it should be checked weekly. Another quick test to do.... when you start up the car, when it says 'oil ok' press the end of the wiper stalk (or is it the stalk off the clocks?!) It then has 5 dots...... the (o) should at least read 4 ish (clarify with edde, i cant remember how to do it!)