Uno 1.7 Diesel Oil Light

Hi Guyz!

Well im back with a problem. Since last one week when I crank the engine of my 1.7 Diesel Uno (cold) the oil warning light comes on and stays on for about 5 - 10 secs. This problem has come up since my last oil change. Always ran my car on 10-40 W oil but since it has done almost 50Ks a friend advised me to start using 20-50 oil instead. So I bought Caltex Delo 20-50 grade oil and changed Oil Filter (Crosslands). In the first week it ran okay but having done around 500 kms with this new oil Im facing this problem.

Any Ideas?

Regards,

Omer