Once again.... What oil CURRENTLY for Mercruiser V8?

[Damon]

I know there are lots of posts regarding "what oil for this" and "what oil for that..." But I am still a little confused.

I have a 1990 Mercruiser 350 Magnum (GM 350) and the manual says to use straight weight 40w. I've also seen recent literature saying that Mercuiser now recommends 20-40w.

I run this at high rpms frequently, and want the best protection I can get considering that. What oil weight and brand would you guys recommend?

 

[JonS]

I think for the newer fuel injected motors, they need a multi-grade. But the older carb models need the straight weights because of fuel dilution from the carbs. They newer ones also have a 160 thermostat instead of a 143 to help the fuel injection system work better.

 

[1 FMF]

The straight weight oil recommendation for marine engines is outdated today. For one, conventional (dino) multigrade oils are far different and superior than what they were in the past. Hence the mercruy 25w40 oil. They are more shear stable, although I had oil analysis show the merc 25w40 oil shear to a 30wt after about 10hrs in the merc 3.0L 4cyl.

Also, with a monograde oil you have to consider how cold it will be when you start the motor cold. Most dino 40wt monogrades say for temps > 60F on the bottle, and 30wt's say > 40F. I remember seeing this on castrol oils. I would be hesitant using a straight 40wt conventional oil, along with a 30wt, unless the temps are always greater than 70F outside when you start the motor. Most people from what I hear are using the chevron delo 15w40 oil. The chevron delo or mobil delvac 1300 oils in 15w40 are very good oils for the price- they're shear stable and because they're for diesels primarily they have a high TBN and work well in marine engines, especially carbed motors that may not be tuned. I noticed all the boat stores around here carry it like crazy, but better to buy it elsewhere where it'd be cheaper.

I've been running redline 10w40 in mine. It's a 1993 351w factory marine replacement for merc model 233 1976 year. I run the redline all season, from june thru december in northeast with good oil analysis results. So I'm sticking with that for now. I would think the mobil 10w30 synthetic, or even better the 0w40 (mobil has no 10w40 synthetic) would be a very good choice. If people here keep reporting good things about the mobil 0w40 then I think I will use that since it is cheaper and easier to get vs redline. Also, any of the amsoil oils in 10w40 or 15w40 would be a very good choice too if it is available to you.

 

[userfriendly]

If your engine "sheared" an SAE 40 down to a 30 weight in only 10 hours, perhaps it needed an SAE 50 engine oil.
Did all of the SAE 40s you tested degrade that rapidly?

 

[1 FMF]

quote:

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Originally posted by userfriendly:
If your engine "sheared" an SAE 40 down to a 30 weight in only 10 hours, perhaps it needed an SAE 50 engine oil.
Did all of the SAE 40s you tested degrade that rapidly?

---

this was the first oil analysis done end of last summer on a 2002 19' Bayliner with a merc 3.0L 4cyl. I bought boat as a salvage, previous owner had the boat in the water about two weeks before I received it. I ran it for about 10 hours then drained the factory fill and caught a sample. I "assumed" the mercruiser factory fill is their merc 25w40 oil. Dyson analysis reported back that the sample viscosity was 11cst @100C. All other analysis #'s were good. The small drop in viscosity doesn't suprise me at all since the motor was brand new and I had been skiing with it most of the time at 4000-4200 rpms. I also don't know what a virgin sample viscosity #'s are, merc 25w40 might be on the low side of the 40wt's to begin with. We'll see how redline 10w40 holds up.

[ August 19, 2003, 10:25 PM: Message edited by: 1 FMF ]

 

[userfriendly]

1 FMF;
If your anywhere around Bridge Port, could you give my lawer a slap up-side his head for me?
Take a look at some of the new single 30s and 40s like Mobil's 1330 and 1340.
We have Pet-Can's high VI singles HDMO Duron.
Those oils flow a lot better in cool temperatures than cheap re-packaged who bottles what for whom motor oils.
I see Shell droped their 25W40 marine oil.
Good. I bought about 3 cases of the crap.
Boy, that 3.0 must be breakin' its balls in a 19 foot BL.
Some day you will have to see what temperature the oil is running at.

 

[Schmoe]

Delvac 1300......hmmmm... have to think about that one. I've been running straight 40 weight Pennz. purebase in my 3.0 and have noticed the oil pressure remains constant at towing or idleing.
Actually, the 3.0 is rated at about 140 hp. Plenty of power on a 18 or 19 footer. Sure, it won't scream out 70 mph, but you can get a good 40 to 50 depending on prop and tilt sittings.

[ August 20, 2003, 09:36 AM: Message edited by: Schmoe ]

 

[1 FMF]

quote:

---

Originally posted by userfriendly:
1 FMF;
If your anywhere around Bridge Port, could you give my lawer a slap up-side his head for me?

---

...then again I would gladly slap any lawyer

the 3.0L @ 135hp does real well in the boat, it tops out around 45mph and it's great on gas.

 

[Bluestream]

This is from the Mercury web site:

What type of oil should I use? Can I use synthetic oil?

To help obtain optimum engine performance and to provide maximum protection, we recommend the use of Mercury Precision 4-Cycle 25W-40 Marine Engine Oil. This oil is a special blend of 25-weight and 40-weight oils for marine engines. If not available, a good grade, straight weight, detergent automotive oil of correct viscosity, with an API service rating of SH,CF/CF-2 may be used.

In those areas where Mercury Precision 4-Cycle 25W-40 Marine Engine Oil or a recommended straight weight oil is not available, a multi-viscosity 20W-40 or, as a second but less preferable choice, 20W-50, with API service ratings of SH,CF/CF-2 may be used.

IMPORTANT: The use of non-detergent oils, multi-viscosity oils (other than Quicksilver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality oils or oils that contain solid additives are specifically NOT recommended.

The table below is a guide to crankcase oil selection. The oil filter should always be changed with the engine oil.

AIR TEMPERATURE
Oil Type

All Temperatures
Mercury Precision 4-Cycle 25W-40 Marine Engine Oil

Below 32? F (0? C)
SAE 20W

32-50? F (0-10? C)
SAE 30W

Above 50? F (10? C)
SAE 40W


This crankcase oil recommendation supersedes all previously printed crankcase oil recommendations for MerCruiser gasoline engines. The reason for this change is to include the newer engine oils that are now available in the recommendation.

Older owner manuals, service manuals and other publications that are not regularly updated will not be revised to show this latest engine oil recommendation. Current owners manuals, service manuals and other service publications that receive regular updates will receive this revised recommendation the next time they are updated.

[top]


© 2003 Mercury Marine

 

[Dick in Falls Church]

Sounds a bit familiar

Saab said don't use synthetics, until they got one with their name on it.

Harley said don't use synthetic, until they got one with their name on it.

GM said don't use synthetics, until they had a mechanical engine problem solved by synthetics. But they still recommended against the use of synthetics in any of the other engines.

Is there a pattern here?

 

[TooSlick]

My neighbor runs the Amsoil 15w-40 in his 37' Sea Ray with twin, 454 Mercruisers. Oil analysis after 125 hours show the oil is in excellent shape and he has reduced his fuel consumption by 5% and picked up 300 rpms at the top end. I think they're nuts, quite frankly ....

Tooslick

 

[Jelly]

15w-40

Chevron Delo 400
Mobil Delvac 1300
Pennzoil Long-Life
Shell Rotella-T

 

[Schmoe]

Just changed/winterized the boat this weekend and used Pennz. Long Life. Oil pressure held surpizedly well during the final shake down run. Even after running hard to immeadiate idle, still holding 40 psi. Think I'll stick with this stuff for a while.

 

[Jelly]

quote:

---

Originally posted by Schmoe:
Just changed/winterized the boat this weekend and used Pennz. Long Life. Oil pressure held surpizedly well during the final shake down run. Even after running hard to immeadiate idle, still holding 40 psi. Think I'll stick with this stuff for a while.

---

Did you use the 15w-40?

If so, did you notice much difference between the straight-weight oils you were running before? Easier starting, etc, etc...

 

[Steve S]

Damon, most all marine engines are run at elevated rpm's .As mentioned above the 15/40 oils are about the best you can get. Using synthetics? Amsoil 15w/40 or Redline 10w/40 or their Diesel 15w/40 will work . Straight 40 will work well if your ambient temperature is with in the 40 wt. area. I have tried lesser weight oils . use the 15w/40 or the straight 40.Boats are different than cars. Look up uoa's of marine engines.

[ September 29, 2003, 10:50 AM: Message edited by: Steve S ]

 

[Schmoe]

You know, I never thought about it, but it did seem to crank over quicker once I got the old stuff out. Oil pressure didn't jump up to 60 right at the start for a couple of seconds before like it used to with the straight weight stuff. Wow. Just now noticed that. Feel better about this oil already. Yeah, it was the 15W-40 Pennz. LL @1.72 quart at Advance Auto. Had to use the PowerFlo filter though. They said it was a Purolator but it's packaged differently because they sell it as a fleet filter. Looked the same. They were out of the AC Delco 1218 and the Purolator equivalent L30040.

[ September 29, 2003, 03:47 PM: Message edited by: Schmoe ]

 

[wulimaster]

My brother has a 22' Sea Ray that he uses at Lake Havasu and 2 weeks ago I was out there with him and got to talk to the local marine mechanic. I asked him if they had to syphon the oil out because there is no way to drain the Mercruiser (305 v8). He said yes.

If I had to depend on syphoning the oil out for oil changes, I would want the best synthetic I could get to help avoid sludge buildup.