oil top up

[boxster]

i have a 986 and i usually use bp fully synthetic oil 0w40.
now i need to top up about 1/2 a litre, but i cant seem to find any of the oil i usually use anywhere, everyone is telling me that its out of stock.
can i add up with another brand, given that its got the same viscosity, will i do any harm to the engine?

[tonycarreon]

you'll be fine