What Oil Weight should I use ???????

Johnny Be Cool

Petty Officer 2nd Class
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Jul 22, 2010
Messages
126
I have a 1990 Regal 233 XL Ambassador (Cabin Cruiser Type) - carburated Mercruiser 5.7 (350 ci). I live near the border of Missouri & Arkansas, all lake water use. I would like to know what weight and brand of oil to use. I've had a number of people tell me straight 40 or 30, 10-40 or 10-30 and use mobile1. Mostly I heard straight 30 for Northern boats and straight 40 for Southern. Thanks to all that reply!
 

legoman67

Chief Petty Officer
Joined
Oct 16, 2008
Messages
636
Re: What Oil Weight should I use ???????

10w-30 is the most commonly used for any small block
 

HT32BSX115

Supreme Mariner
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Dec 8, 2005
Messages
10,083
Re: What Oil Weight should I use ???????

Hmm,


You missed yesterdays oil thread! Your's can be today's ;) Seems like this question is asked about every day or so.....:rolleyes:


If you do not want to use the oil that Mercury recommends,

You can use what ever you want. Marine engines don't fail due to brand or type of oil. Everything has been tried successfully.


Cheers,


Rick
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,802
Re: What Oil Weight should I use ???????

Merc says their 25/40 or straight 40...
I would not use a 10w-30 in a marine inboard...more likely to break down...as long as your boating temps are moderate the straight 40 will be fine...
OMC and Volvo recommended straight 30....Merc straight 40 for the same base engines...go figure...
 

Fishermark

Vice Admiral
Joined
Oct 19, 2003
Messages
5,617
Re: What Oil Weight should I use ???????

Merc says their 25/40 or straight 40...

Well, Mercruiser has a few more choices than that. And the straight 40 or straight 30 depend upon the temp....


faqs_temp.gif
 

Johnny Be Cool

Petty Officer 2nd Class
Joined
Jul 22, 2010
Messages
126
Re: What Oil Weight should I use ???????

Now I'm confused????????
Weather temps would be around 70-99 degress.
I'd be running 15-20 minutes at a time.
I'm thinking straight 40.
Any other opinions, please advise!
Thank you
 

Philster

Captain
Joined
Sep 15, 2009
Messages
3,342
Re: What Oil Weight should I use ???????

Anything from straight 40 on up the chart to other options listed. Straight 40, according to Merc, is the 4th best option.
 

sethjon

Senior Chief Petty Officer
Joined
Jun 8, 2010
Messages
692
Re: What Oil Weight should I use ???????

I have a 1990 Regal 233 XL Ambassador (Cabin Cruiser Type) - carburated Mercruiser 5.7 (350 ci). I live near the border of Missouri & Arkansas, all lake water use. I would like to know what weight and brand of oil to use. I've had a number of people tell me straight 40 or 30, 10-40 or 10-30 and use mobile1. Mostly I heard straight 30 for Northern boats and straight 40 for Southern. Thanks to all that reply!

I use 10-40 on all motors and never had a problem. Great in all kinds of weather. Use a top notch brand.
 

IES99

Petty Officer 1st Class
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Jun 3, 2008
Messages
271
Re: What Oil Weight should I use ???????

Tomorrow it is my turn to ask this question. :D
 

carolynrose

Petty Officer 3rd Class
Joined
Oct 29, 2008
Messages
99
Re: What Oil Weight should I use ???????

Just my 2 cents. In my 30+years as a GM master tech, all the classes I've been to, GM was very insistant not to use 10w40 in any of their engines. There a ton of 350 GM engines out there in boats. Unlike a car engine, boat engines run at a continuosly higher rpm. I would recommend the 30 or 40 weight oil that the service manual says. It is very unlikely that you operate your boat engine in below freezing temps, so the need for the 10w oil in multi viscosity oils isn't needed. Remember 10w30, the w stands for winter
 

Johnny Be Cool

Petty Officer 2nd Class
Joined
Jul 22, 2010
Messages
126
Re: What Oil Weight should I use ???????

Thanks to all for giving your opinions.
I'm thinking of staying with a straight 30 or 40, therefore what is the difference between the two and their applications.
Under what circumstance should I run 40 or 30 weight.
Thank you!!!!
 

elkhunter338

Master Chief Petty Officer
Joined
Jun 27, 2009
Messages
818
Re: What Oil Weight should I use ???????

30 is going to be less thick when cold. if you are always boating with temps well above freezing go with either 30 or 40.
I would stick with a diesel grade oil, in a 30 or 40 weight. you will not have any trouble.
 

Johnny Be Cool

Petty Officer 2nd Class
Joined
Jul 22, 2010
Messages
126
Re: What Oil Weight should I use ???????

Go Figuire???????????
Mercruiser suggested Quick Silver 25w-40 or straight 30
I appreciate everyone's opinion. Thank You and Happy boating!!!!!!!!!
 

sethjon

Senior Chief Petty Officer
Joined
Jun 8, 2010
Messages
692
Re: What Oil Weight should I use ???????

I use 10/40 and never had a problem but straight 40 is fine.
 

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: What Oil Weight should I use ???????

nothing that starts with a 10 or a 5 unless boat has an engine oil cooler (i.e. some Volvo Penta)
i.e. I agree with Mercruiser
 

sethjon

Senior Chief Petty Officer
Joined
Jun 8, 2010
Messages
692
Re: What Oil Weight should I use ???????

Thats true so its really just for starting. Sometimes I think the engineers put out those specs because they don't do enough research.
 
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