Oil on kv6

My beloved MG ZT 190 has just been serviced and I noticed that they put 5w30 Midland Oil fully synthetic on. Normally I run it on 5w40 and am a bit worried that this oil is not good enough. What should I do? Is it safe to drive with the 5w30 or should I go back there Monday morning and make them change for 5w40?



Best regards

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