freelander 2.0 DI oil light staying on ?

Hi hope someone can help with problem,when i start the engine oil light sometimes stays on, i boot the accelarator and it goes out will not come on again for length of journey no matter how long, will only come back on if engine is stopped and restarted. I would say it happens about 80% of the time,there is no engine managment light on,i have change oil prsure switch and dropped the oil still the same please help!
FREELANDER 2.0 DI W REG 2000

Are you using the correct grade of oil?
have you got a good seal around oil cap and dip stick?
L-series are prone to oil leaks around oil filter.
If it stays on when driving it would be a problem, could be worn engine bearings and oil pump or faulty pressure relief valve.
If it goes out when you run the engine and the oil level is correct then you could put it down to it being nearly 10 years old.

not sure wheather it would stay on if i did not rev it up before driving off,should i try without reving up ? also what grade oil would you recommend cheers

Might aswell try, just check the oil level first and don't go too far from home.
Is it burning oil?

L series engine is quite robust but does need frequent oil change.
See if light goes out at tickover (may off, on, off), if so could be oil pump which needs coat of oil before getting to pressure and is just a sign of normal wear.
What milage has it done.
PRV could be faulty.
Will not give engine management light as this is mainly for emission control and 2000 was when most manufacturers were still using OBD1