There is most likely a larger acceptable lower limit range for the oil level to be “OK” for on road use versus off road use because for off road the vehicle may be at more severe off camber angles than on road and if down on oil it may cause an oil starvation issue. Most likely anything below 500ml full is where the lower limit is for off road. Hence you are fine to add 500ml as that would bring you up to the ”OK” range for both on road and off.For info I just carried out an oil check in a diesel N1 5 seater post c830miles, all looks ok albeit my instinct would be to put in another 500ml to be on safe side on and off road (can this be done or is the vehicle then over filled for road use?)
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