Just had a service done by our local mechanic on our fiat bessacar 2.8jtd & just noticed that the service sheet says 6.5 Litres 5w30 semi synthetic oil.I believe 10w 40 semi is the correct grade to use on this engine so was wondering if i should have it changed again or will it be ok to leave until the next service.?If not can i just drain the oil & refill with correct grade without having to take off the oil filter?.