A friend of mine has recently bought a 56-plate 1.3JTD (90bhp - 6speed). The car has 130k miles on the clock. A local motor factors advised him to use 10W40 oil grade, saying that he needs to use thicker grade due to the car's mileage. Since replacing the oil, the oil warning light flickers and stays on whilst the car is idling; the warning light goes off when my mate depresses the accelerator. Could this be an oil pressure issue, due to the use of wrong grade? (Fiat recommends 5W40, not 10W40). Could it be something else?

What's the point of using 10-40 over 5-40 anyway? It's the same hot viscosity (40)

Can't see the point...anyway make sure it has the same ACEA.

I don't think there is a pressure problem just by the oil type.

Check filter etc again.