Oil mix?

[imotep]

Hi guys, not sure on the oil type in my surf and it could do with a top up so will it hurt 2 put some castrol gtx magnatec in? Or should I do an oil and filter change, its not due for a change till Xmas, only asking as its got a lot of miles over the next week. Thanks for any help, Karl.

[stormforce]

if your doing alot of mile then its just aswell to do an oil and filter change