Still confused

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I am still confused about replacement oil for a Mercruiser 3.0 In one response a person states
his brother uses a 15W-40. My manual does not mention this. It states use a straight 40w.
The confusion comes in at the ASP applications.
Which one should I use?
I agree that the Mercury product is too expensive, and hard to find
 
I use 15w-40 John Deere CH-4/SL rated oil in my little 15hp Suzuki 4 stroke outboard with no problems. Next change will be using Schaeffers 15w-40 Synthetic blend oil.
 
Bill,

I'd use Delvac 1300, 15w-40 ...here's why:

Please take the time to either cut and paste or explain. sorry but we do not allow posting of another forum to answer questions.

[ October 11, 2002, 03:01 PM: Message edited by: BOBISTHEOILGUY ]
 
Bill,

There is no right or wrong to every application. The difference between the two is this.. for cold weather applications the 15w40 is preffered for better startup.. but after it has warmed up, they both will act the same(in theory). Now given they both are a 40wt, the straight 40 is normally more shear stable meaning it will hold it's viscosity better due to the fact it doesn't rely on VI improvers. (we are talking mineral only) Now when you take a boat out, most do this when weather is good and usually warm so the pour point issue of a 15w doesn't even come into play for this much if any at all.

If you can run a 15w40 without plug fouling,or oil burning, then you will be alright with that, but many times especially with diesel engines you want to run the straight 40wt for marine applications. In diesel applications, most run a min of 200hrs with the standard delo 400 and I have many running up to 1000hrs on the schaeffers 107 40wt.

In a gas engine application you should be able to run it between 75-150hrs(3750-7500miles) before needing to change it over depending on oil analysis.

My main concerns is this, 1- manufacture states using 40wt, then I recommend 40wt. It is always advisable to stay with the recommendations. Only reason to deviate from this is, oil burning or based on oil analysis oil is failing. Other than that, no change should be recommended.
2- problem is, if the 15w40 is burning through or plugs are fouling out, then you need to maintain the 40wt.

IMO, if it was mine, I'd be using the straight 40wt. Why rock the boat if it isn't giving you any problems?

BTW FYI, I had a marine diesel that I put on to the 15w40 blend, and it worked with the exception it burned oil past the rings, switched to the 40wt, recommended by the engine manufacture, consumption went way down.
 
Bill,

The best Group II/II+, multigrade 15w-40 oils are very shear stable. There should be no issue with running the Delvac 1300 or Chevron Delo 400, either in terms of shearing, oil deposits or oil consumption. All of the latest basestock and additive technology is going into the multigrade stuff. These oils are formulated for use in HD gas/diesel engines that run under very high, sustained loads and temps.

If this engine were in a car, it would recommend a 5w-30 or 10w-30 oil. However, in a marine application the loads are significantly higher and you can sometimes have issues with fuel dilution. So using a 15w-40 or even 20w-50 - in an older motor - is preferred.
 
It's really amazing how different parts of the country has their prefference.

Out here in Jacksonville Florida, which happens to have lakes but also salt/freshwater river(st johns river) and let's not forget a whole big ocean where Jacksonville is located at..(called the atlantic) just for those of you inland.. but around here,where we have a tremendous amount of boats for all types of applications, most prefer using what is recommended by manufactures and for that, most are the straight 40wt.
 
I just picked up a 2002 bayliner with a 3.0L merc I/O. So I am going throught the same dilemma you are. I found some Mercruiser TSB's.
http://www.bravodrives.com/bulletins_main.html

look for 97_23.pdf that was the latest one concering which oil to use (Merc 25w-40 of course) but also explained what different oils were acceptable and could be used. Basically they say their 25w-40 is best because it won't shear like a 10-40 or a lower 30wt oil. Also, if you trace back a few years you can read how their recommendations have changed, which gives you an idea as to which oil might be best.

I just changed the oil in the bayliner and went with castrol 30HD. The motor still runs fine, oil pressure guage sits right at 40 all the time.
I will probably just go with a synthetic 10w-40 or 20w-50 next season. Just did oil analysis on the factory oil, will post the results in a few days for ya.

here is 97_23.pdf :

quote:


MerCruiser Gasoline Engine Oil Recommendation
Change
The following 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.
Crankcase Oil
To help obtain optimum engine performance and to provide maximum protection, we strongly recommend
the use of Quicksilver 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 Quicksilver 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 chart below is a guide to crankcase oil selection. The oil filter should always be changed with the engine
oil.

 
Bill, I was the one who stated that we use 15W-40 in my brother's 3.0 Merc. It costs around $5 at Walmart for a gallon. In Savannah, we boat 10 out of the 12 months, so we change the oil twice a year. His manual recommended the 25W40 Quicksilver oil, but says you can use 20W-40 or Straight 40W as alternative oils. We have had good luck with this oil. There was some discussion on this topic in this thread: http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=13;t=000002

[ October 25, 2002, 09:55 AM: Message edited by: BOBISTHEOILGUY ]
 
In laymens terms what they are basically recommending is a straight weight, light duty diesel oil, or heavy duty multigrade, gas/diesel oil - ie a 15w-50/20w-50 "motorcycle" oil. Light duty diesel oils do a better job of protection against rust and corrosion, since they use high levels of alkaline detergent/dispersant additives.

If you want an off the shelf oil for this application, I'd run Mobil 1, 15w-50. It meets the CF and ACEA B3/B4 light duty diesel specifications.
The baseline TBN is in the 11-12 range and you can substitute the 15w-50 synthetic for the 20w-50 petroleum oil ....I'd expect it to shear down by perhaps 10% in this application, but that will have no effect on the wear rates. After a 50 hour break in period with the Mercury oil, I'd switch to the 15w-50. Do an oil analysis test @ 30-40 hours and post the results ....I'd be surprised if you can't run 100 hr/1 year drain intervals, with just a filter change @ 50 hrs.

These Mercruiser engines are nothing more than glorified GM V-6's or V-8's, so there is no reason why a synthetic engine oil that meets the API specs cannot be used. This is not just theory but from personal experience running 15w-40 synthetics in the 5.0L and 7.4L Mercruiser engines ....
 
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