85sportfire
New member
What brand of 4-stroke oil does everyone run in thier I/O boats?
Anyone running synthetic?
Anyone running synthetic?
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What brand of oil does everyone run in thier boats?
- Thread starter 85sportfire
- Start date
For some unknown reason, Mercury specifically said NO synthetic in the 2003 4.3 I had. I was at a dealer this week, and noticed the 2008 4.3 Volvo package specifically stated 30W full synthetic in it's engine. WTH? Same engine! Different paint!
So for my mercruiser, I ran the Mercury spec 25W-40 and nothing else. It's supposed to be a special blend of 25W and 40W, NOT an oil with additives that make it act like a 'car' oil.
I did run 100% marine synthetic in the drive, and used a Simrec drive shower.
I should go to a dealer and find a new '08 Mercury 4.3 and see what is recommended for oil. Maybe the brand new mercruiser is recommending the same as the volvo now...............
So for my mercruiser, I ran the Mercury spec 25W-40 and nothing else. It's supposed to be a special blend of 25W and 40W, NOT an oil with additives that make it act like a 'car' oil.
I did run 100% marine synthetic in the drive, and used a Simrec drive shower.
I should go to a dealer and find a new '08 Mercury 4.3 and see what is recommended for oil. Maybe the brand new mercruiser is recommending the same as the volvo now...............
Chris E
Well-known member
that's what they said in a mercury service bulletin only use 25w40, which is basically a mix of 25w with 40w splitting the difference it is actually 33w - but who's counting?
i run amsoil 15w40 in dad's 4 banger sea ray - primairly because we run it around 3800 rpms
the 2 volvos i winterize also get the amsoil treatment - they specifically recommend synthetic oil.
i run amsoil in the drives as well, although the merc gear oil is excellant as well - it doesn't flow as nice as the amsoil in cold weather though.
i run amsoil 15w40 in dad's 4 banger sea ray - primairly because we run it around 3800 rpms
the 2 volvos i winterize also get the amsoil treatment - they specifically recommend synthetic oil.
i run amsoil in the drives as well, although the merc gear oil is excellant as well - it doesn't flow as nice as the amsoil in cold weather though.
Walt Woolvett
New member
What do the rings and bearings think.
Mercury doesnt build the motors that I know of. They are built by General motors and dont think they use different bearings in marine engines bur I could be wrong. They are not listed any different in the bearing and ring catalogues.Mercedes Benz being what it is usually recommends a different weight oil for diferent temps and has a good tech base behind their decisions.Used to be #30 at one time. A fluid wedge in the bearings and a film on the cylinder was and is the basic requirement of all engines.One thing for sure is if its on warranty you better use whats recommended or the oil test will let them off the hook. Good old CTC rates their oils right up there, but who would use them. SF or better ratings usually cover a lot of applications.
My 2 cents worth.
Mercury doesnt build the motors that I know of. They are built by General motors and dont think they use different bearings in marine engines bur I could be wrong. They are not listed any different in the bearing and ring catalogues.Mercedes Benz being what it is usually recommends a different weight oil for diferent temps and has a good tech base behind their decisions.Used to be #30 at one time. A fluid wedge in the bearings and a film on the cylinder was and is the basic requirement of all engines.One thing for sure is if its on warranty you better use whats recommended or the oil test will let them off the hook. Good old CTC rates their oils right up there, but who would use them. SF or better ratings usually cover a lot of applications.
My 2 cents worth.
Last edited:
stclairriverblaster
Member
i use royal purple in my lower units.. 
bigsbetter
Active member
Mobile 1 full synthetic
Turbot-bird
Member
Amsoil all fluids
hotdaddy27
Well-known member
Those of you that run Royal Purple...
What weight gear oil are you running. 75/90, 80/90, 85/140 or straight 90.
Thanks.
What weight gear oil are you running. 75/90, 80/90, 85/140 or straight 90.
Thanks.
Old Navy
Active member
I run the RP 75w90 in the drive. My friend did an experiment and found that by switching from RP 75w90 to the heavier 140 weight, he lost a couple MPH. So far my drive has held up, using RP exclusively after it got rebuilt, time will tell.