Synthetic oil

[TheOilDoc]

Re: Synthetic oil

It's not uncommon in many parts of the country for boats to operate in climates below 32F.<br /><br />BTW, a straight-weight oil doesn't appear to be their highest recommendation below 32 degrees.

 

[imported_Curmudgeon]

Re: Synthetic oil

Why does my service manual and for that matter the service bulletin that DonS posted, list straight weight viscosities for operating below 32 degrees?<br /><br />Not sure about your service manual, but the bulletin lists straight weight as #5 in a priority order of ... 5. And the multi-viscosities are good for all temps one would realisticly expect to operate a marine engine. And the bulletin superceeds all other printed recommendations (including owner/service manuals).

 

[lorax]

Re: Synthetic oil

I guess the question was really rhetorical.<br /><br />I've always found it a little odd that the Merc oil charts, in a factory servcice manual, provide middle temp range from 32 to 50 degrees F. Assuming the chart is somewhat linear, the highest air temp on the chart would be 68F<br /><br />90% of my boating happens between 80 and 100 degrees. <br /><br />But that's just me.

 

[Don S]

Re: Synthetic oil

The chart was never meant to be linear. Look at it again, there is no upper, or lower limit. If you boat in 100° weather, and wish to use a single grade oil, then you would use the 40W. Yes, there is a narrow band of where 30W should be used, but that only means Merc found the other weights worked better at over 50° or under 32°.