Be very careful with this one. Agreed with contacting insurer and getting it in writing. Reason for this is your MR states 50hrs or 4 months. If the engineer didn't put +/-5hrs adjacent to the 50hrs I would stick to the 50hrs, especially if no letter comes from the insurer. Unlikely an engine failure will occur due to stretching the change of oil and filter an extra 5 hrs. But, murphy reckons it'll happen. Highly likely then the insurer is gonna 'say sorry pal you didn't stick to your MR requirement .... I don't care what AD/ENG/4 says, cos your MR says 50hrs'.
You could just save yourself the trouble and get the oil and filter changed before you go. It shouldn't take any longer than an hour or two and you'll have nothing to worry about.
