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15w40 or synthetic 10w30 for 115°f temps #5135042
06/15/19 03:29 PM
06/15/19 03:29 PM
Joined: Jan 2014
Posts: 524
AZ
leroyd92 Offline OP
leroyd92  Offline OP

Joined: Jan 2014
Posts: 524
AZ
I have 2 boats with 350 engines in them. I've always used 1540 or 2050 in them but I've been curious if I'd gain anything from a full synthetic 10w30.

Engine RPM never goes past 4k

We cruise them at 3k.

My only concern is certain spots of water can we warm especially late in the summer.

What are your thoughts?


Supertech Junky
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135043
06/15/19 03:32 PM
06/15/19 03:32 PM
Joined: Feb 2014
Posts: 3,046
Canada
Lolvoguy Offline
Lolvoguy  Offline

Joined: Feb 2014
Posts: 3,046
Canada
Originally Posted by leroyd92
What are your thoughts?

Why change what's working?
Only difference I could see, is additional cost to you.


06 Lexus IS350- Wife
88 BMW 325is- Mistress
Say "no" to Turbo!
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135061
06/15/19 03:53 PM
06/15/19 03:53 PM
Joined: Jun 2003
Posts: 19,189
Apple Valley, California
Chris142 Offline
Chris142  Offline

Joined: Jun 2003
Posts: 19,189
Apple Valley, California
The water can't be nearly as warm as the ambient air temp or the water coming out of the radiator.


02 Wrangler traveler sae30
87 F250 Valvoline 15w40
07 fjcruiser Chevron 10w30
Z400 castrol T 10w40
Can am maveric edge 5w40
57 case tractor Chevron sae30
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135063
06/15/19 03:58 PM
06/15/19 03:58 PM
Joined: Oct 2004
Posts: 9,139
Cincinnati, OH, USA
bullwinkle Offline
bullwinkle  Offline

Joined: Oct 2004
Posts: 9,139
Cincinnati, OH, USA
Unlimited cooling water supply, most marine engines have relatively low temp thermostats in them, I would stick with the 15W40.


06 Ram 3500 CTD 4X4(FG Venturi), 93 GMC C3500 6.2, 89 F-450 7.3, 98 XJ 4.0(XG8A), 05 xB(XG3600), 18 Transit 3.7, 03 Merc Grand Marquis 4.6 2V(XG2)
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135124
06/15/19 05:56 PM
06/15/19 05:56 PM
Joined: Nov 2012
Posts: 706
Ajax,Ontario, Canada
Pelican Offline
Pelican  Offline

Joined: Nov 2012
Posts: 706
Ajax,Ontario, Canada
Originally Posted by leroyd92
I have 2 boats with 350 engines in them. I've always used 1540 or 2050 in them but I've been curious if I'd gain anything from a full synthetic 10w30.

Engine RPM never goes past 4k

We cruise them at 3k.

My only concern is certain spots of water can we warm especially late in the summer.

What are your thoughts?


Don't they require marine oil?

Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135199
06/15/19 07:41 PM
06/15/19 07:41 PM
Joined: Nov 2011
Posts: 1,679
Lyndhurst NJ
Audios Offline
Audios  Offline

Joined: Nov 2011
Posts: 1,679
Lyndhurst NJ
Keep doing what works. I dont think theres anything to gain here except if you were running longer intervals perhaps.


2002 VW Golf TDI-T5 10/30
2007 Mercedes GL320 CDI- M1 0/30 ESP
2005 BMW M3 BMW Twin Power 10/60
2003 BMW M5-Fuchs 5/40
1998 BMW M3/4/5 Fuchs 5/40
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135202
06/15/19 07:48 PM
06/15/19 07:48 PM
Joined: Sep 2014
Posts: 1,664
Seattle-ish, WA
Oro_O Offline
Oro_O  Offline

Joined: Sep 2014
Posts: 1,664
Seattle-ish, WA
What you could gain is running a straight-weight oil if the brand/weight you want comes in that offering.

Running a winter rating is pointless for a vehicle not started below freezing (I'm making an assumption here about your use of it), and you sacrifice by having a lighter base oil and non-lubricating and potentially shearing VIIs in it.

Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135283
06/15/19 09:09 PM
06/15/19 09:09 PM
Joined: Oct 2014
Posts: 1,520
NoVA
Jimzz Offline
Jimzz  Offline

Joined: Oct 2014
Posts: 1,520
NoVA
15w40 would get my vote. Good all round oil that can handle high heat and even cool temps you may see.


yup
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135336
06/15/19 10:35 PM
06/15/19 10:35 PM
Joined: May 2012
Posts: 6,710
Fort Lauderdale, FL
DoubleWasp Offline
DoubleWasp  Offline

Joined: May 2012
Posts: 6,710
Fort Lauderdale, FL
Don't do it. The 30 weight thing has been tried by the manufacturers before. Didn't work. Wear problems popped up like whackamoles.


07 Lincoln Navigator M1 0w-40/FU
68 Charger R/T / Supercharged 440 VR1/DBL7349
07 Ram 3500 4x4 / Cummins 6.7 /DBL7349
17 Maserati GranTurismo Cabrio
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5135345
06/15/19 10:50 PM
06/15/19 10:50 PM
Joined: Jan 2017
Posts: 166
Alaska and Wisconsin
SteveG4 Offline
SteveG4  Offline

Joined: Jan 2017
Posts: 166
Alaska and Wisconsin
Stick with the 15W-40 usage.


Somewhere between Alaska and Wisconsin...
2006 Silverado LT Crew Cab 4WD & 2013 Equinox AWD
Re: 15w40 or synthetic 10w30 for 115°f temps [Re: leroyd92] #5136298
06/17/19 05:37 AM
06/17/19 05:37 AM
Joined: Jul 2012
Posts: 2,996
South Carolina
alarmguy Offline
alarmguy  Offline

Joined: Jul 2012
Posts: 2,996
South Carolina
20w50 all the way, way more so for your hot climate.

15/40 acceptable but would prefer 25/40 is you were to go down to a 40.

10w30 to me would be insanity and I think all you would need to do is try it out, then run the boat for an hour or two at 3000+ RPM, slow down and listen to your valves clap.

Most marine engines have 170 degree thermostats in them so it doesnt matter too much as far as water temperature that the boat is running, unless you have closed cooling, then you may have a 190 thermostat..

Oil temperatures do not correlate to water and engine temperature. An engine with a water/coolant temperature of 170 degrees will see oil temperatures well over 200 degrees, there is nothing cooling the oil and your engine compartment is pretty much closed.
This isnt an automobile with 4 smooth rolling wheels, this is a log (boat) being pushed through water with a lot of engine and bearing pressure which greatly adds to the temperature of the oil.

(just my thoughts)

Ps. I always followed the manufacturer which was 25/40 in my mercruisers and now with a Volvopenta engine the book also states 20/50 as an option that I choose to use.
Actually currently using 15w50 Mystik JT8 semi syn this year in our new to us Chaparral.

Last edited by alarmguy; 06/17/19 05:41 AM.

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