Can I mix 5w-30 and 5w-40?

[Danger]

Hi All,

I'm out in the sticks and the low oil volume warning has come on. The car currently has castrol edge 5w-30 and the only oil I can find locally is castrol edge 5w-40. Is it ok to mix the two?

The engine is a 2008 2.0TDI PD non DPF.

Thanks

DP