oil for 5.0 mercury

[sbryant9677]

owners manual states a 25w - 40 marine motor oil, is this a must or can you use a good synthetic such as mobil 1 10 40 or compairable or any grade recommendations. cannot seem to find any marine oil local and have plenty of mobil 1 handy.. thanks in advance!!

 

[guyjg]

It will work. I use Mobil 1 15W50 in my 4.3L. If you only boat in warm weather you can use straight 40 weight or 15W40 mineral oil. AC Delco Delvac or Shell Rotella 15W40 oils are high quality engine oils which I have used.