Synthetic oil

I have 2 DD 6-71's 485 A f

I have 2 DD 6-71's 485 A friend recommended I use synthetic oil instead of regular 40 weight. I recently did an oil change and each enging took about 6 gallons of oil. I must say that I dont know of anyone who uses synthetic on their boat. Any comments would be appreciated pros-cons?

"I trust you have been using o

"I trust you have been using oil that is rated for use in diesel engines and not for gasoline engines only. Synthetic oil has very little, if any, advantage over petroleum based oil in reciprocating engines. At the greatly higher cost it simply does not make sense. Most of the longevity increase came from advance in the additive packages that are put in by the manufacurer. That level of effectiveness is noted as an API rating which is noted on the container label. Myths about crankcase oil top the list of common mechanical myths. A worse belief is gimmick additives. Additive packages in modern oils are a precise chemical balance and can actually be hampered by introducing an outside additive to the mixture."