E46 M3 - can I top up with 10/40?

[trackdemon]

Acquired E46 M3 last week, and promptly threw it into a tour of europe... Great car for this kind of trip, and in Phoenix it still gets some looks despite mixing it up with Ferrari's and Lambo's. I've noticed the low oil level warning light comes on occasionally, and it looks like it's at the lower end of the dipstick so want to top it up - it's done 1500miles since purchase and I understand they can consume a little bit. Problem is I'm unable to find the precise 10/60 that is recommended, so wondered if I'm ok to top up with a quality synth Castrol GTX or similar - 10/40 IIRC. Will be getting service in 3k miles anyway. I assume it's better to top up with slightly different grade than not at all...?

[trackdemon]

Won't happen today but we're heading to Monaco tomorrow, sure there must be a dealer there or in Nice I can grab some... Otherwise I'll put a dash of the best Castrol fully synth I can find.

[trackdemon]

Excellent thanks! I figured adding 0.5l would not be an issue....