Did Volvo change the recommended oil from 30wt?

[USA_boater]

I keep hearing they now recommend 10w40 in their gasoline motors that were spec'd for straight 30wt? This is for a 4.3GL '04 model.

 

[Scott Danforth]

FWIW, I run rotella T4 15W40 diesel oil in my boat motors

 

[Lou C]

I recall reading they changed from a syn straight 30 to a syn 10/40. What were you using previously?

 

[Scott Danforth]

over the years they changed from SAE 30 dino squeezings to semi syn to syn....

they used to run SAE 30 in the drive as well

 

[BRICH1260]

FWIW, I run rotella T4 15W40 diesel oil in my boat motors

What`s the advantage of running a diesel oil in a marine engine? Just curious.

 

[Lou C]

It used to be higher levels of zddp zinc to protect the flat tappet cams, vs oils for passenger gas vehicles, but if you have a roller cam that is a non issue.
I have used the Mercruiser/Quicksilver 25/40 which holds up well and is available everywhere.

 

[Scott Danforth]

What`s the advantage of running a diesel oil in a marine engine? Just curious.

high Zinc for the cam, lifters and valve train. higher shear modifiers and lower cost than "marine oil"

basically its a really good oil for a boat motor at nearly 40% the cost ($11 a gallon for Rotella vs $27 a gallon for Quicksilver)

while a roller cam reduces some of the need for zinc, it doesnt reduce the need for shear modifiers.

 

[USA_boater]

Yeah my boat has rotella T5 15w40 in it now for same reasons Scott mentioned. I was considering going to a full-syn Marine oil and 10w40 is what I thought I'd run. BUT, I wasn't sure if they changed the recommendation; I don't know what the boat had before since I'm a new owner but knowing my cousin who owned it before me, he didn't take the time to change it every year nor use full-syn...I'm glad it is roller, still has great oil pressure.

I bot a 5 gallon jug of Mobil-1 15w50 on sale half price so that is what is in the garage to replace the Rotella but then I started all this FC-W business in my head and also the fact Volvo says go full-syn...I need ot just forget it and run the Rotella for cost reasons like Scott said...even the T5 which is syn-blend is cheaper than the Quicksilver 25w40...And Sam's club has the T4 & T5 15w40 jugs in cases for even cheaper than they can be bought individually. If not for the deal on the Mobil-1, I'd probably just run the Rotella unless I am convinced that the FC-W thing matters in a 14yr old inboard.

 

[USA_boater]

Any harm in running thicker oil ( bearing clearances)?

So if a boat was originally spec'd for straight 30wt oil and then later the factory changed to 10w40 to supersede and then further someone even wanted to run 15w50 or some other oil that was several viscosities away at op-temp from the original 30wt oil recommendation. I would "think" that in summertime and the higher RPM's that boats often run that the thicker oil would be better anyway but I don't know enough about if running a thicker oil risks lubricity due to bearing clearances? My guess is there is a safe range and in say 70* - 105*F temps 30, 40 or 50wt oils would all be fine?

 

[mr 88]

My 1987 305 Mercruiser straight inboards according to the manual call for straight 30 BUT then it goes on to say if NA use a as a 20-40 for your second choice and finally a " less preferable choice,20-50 may be used " Yes the hotter the ambient temp along with a heavy payload point to a heavier grade and 50wt should be no issue under those conditions.

 

[harringtondav]

If you have your boat's original documentation, see if your engine mfg. included a viscosity-temperature chart. My '96 Merc. 4.3 manual pushes Merc's 25W40, but also states 20W <32 degrees F> 30W <50 degrees F> 40W over 50F. Merc also states 20W-40 or 20W50 are acceptable. I rarely boat under 50F. But I will start it on muffs at colder temps for winterization fogging, oil and drive lube changes. I use synthetics, whitch have better cold start lubrication than conventional engine oil.

So XW-40 is the way to go for summer boating. >50W may be a little too heavy. I've tried to find a 25W-40 full syn, with no luck. Valvoline and Royal Purple offer 40W syns, but they are pricey. The good news is they are a fairly safe bet for two year change intervals, assuming you don't rack up too many hrs.

The average family-mobile probably averages 45-50 mph max in a year. For a 6000 mile oil change that's 120-133 hrs/year. That is a lot of use in a boat year. Condensation, particularly in winter layover is an issue. But I'm good with 2 yr. syn oil changes on my <20hrs/yr boat.

 

[racerone]

Define what -----" lubricity " ---- is in a rotating shaft and bearing.-----Or perhaps explain how water lubricates a ---" cutlass bearing " ----on an inboard propshaft.

 

[MTboatguy]

Really? You are again asking more oil questions?

:facepalm:

 

[alldodge]

Or perhaps explain how water lubricates a ---" cutlass bearing " ----on an inboard propshaft.

When you were in elementary school ever have a kid give you friction burn (called Indian burn where I cam from)?

Two hands are put on your arm, side by side, and gripped tightly, then hands are rotated in opposite directions. The reason for the burn is its "dry" and no lubrication. Add a small amount of water and now it doesn't burn and has some lubrication

 

[racerone]

How does a cutlass bearing ----" work " ----hour after hr in water ?

 

[alldodge]

The old style cutlass, is made of leather, so it swells when wet. It should leak a few drops every so many seconds when the shaft is turning. These drops is how it is adjusted (tightened). For the most part it will not leak when shaft is not turning, unless the leather is worn out and needs replacing.

New style are called drip less and uses to stainless steel plates and carbon disk which is also cooled by water tube to the unit

 

[GA_Boater]

Really? You are again asking more oil questions?

:facepalm:

Only in one thread, not spread all over the forum.

 

[PITBoat]

I tried 20W-50 in my worn out '89 GMC 4.3L to see if it would slow the oil usage, and it overheated - boiled the coolant. That was one of the options in the factory manual too, I believe, depending on temperature. Had to go back to 10W-30 with the occasional 10W-40 or straight 30 thrown in.

 

[Scott Danforth]

I assume a discussion on surface tension would help cutlass bearing discussions.....however it doesnt help the OPs question

 

[QBhoy]

I’m not sure merc ever recommended a straight 30, in response to one of the posts. Not in that era at least. They always went for their own related brand 25w-40
in response to the post. I can’t think of VP saying a straight 30w in as recent as 04 ? Would surely have been their own oil (perhaps that was a 30?) or 15w-40 or similar either way depending on where it’s used. The big thing was that it was GL5 rated. Most of the good brands of 15w40 are. If you are fussy, the quicksilver synthetic blend 25w-40 is decent stuff.