John Wentworth wrote in message ...
WaIIy wrote:

Mercury recommends 25W-40 oil for Mercruiser engines, back in '89 they
rcommended straight 30 weight. In '89 Mercury sold 30 weight and warned
against multi-viscosity oils, now they recommend and sell it.

Interesting, but I am doubtful. I installed 2 new mercruiser 5.7 liter
I/Os in year 2000. The owners manual specified their own 25w-40 with
other multivis as alternatives. It specifically recommended against
synthetic oils. That seemed weird, so I called my friend who has a
1985 mercruiser 5.7 liter I/O. His owners manual was identical in all
respects about oil except it did not say anything about synthetic oil.
Somewhere between 1985 and 2000 Mercury saw fit to add one sentence to
the manual to recommend against synthetics. Neither manual listed
straight weight as a first or second option.