Bill, my opinion is you are starting to push the upper limit on temp. If you don't do anything else, just change the oil more often and get it analysed.

The base stock performance starts going away in high heat conditions. The base stock starts to oxidize, carbon molecules start joining together and start forming "longer chains" which in turn start to thicken up the oil. Oxidized oil when drained is thicker than it should be and black. In extreme cases the oil will glug out of the pan, if it moves at all, when you do an oil change.

Synthetic base stocks have more oxidative stability than petroleum stocks.

ZINC, that all important additive for engine wear is also multi-functional. It helps oil from oxidizing. Not only is it a anti-wear additive, but it is also an anti-oxidant. Another point for zinc.


If it is possible to knock another 20 degrees out of your oil on both ends, running temp 220ish and WOT 270ish, the oil would give you longer life.

My 2 cents.
Ken

Ken,

Certainly worth a lot more than 2 cents. Thanks.

What (values) in the oil analysis should be looked at to identify / red flag that the oil has been oxidized to the point it should be changed?

Thanks,

Bill

I am hoping you are checking a used sample against a retained sample of the the same oil.

That said,

the additives will show depletion, values will be lower and on a
report with "normal" use, the viscosity will be less.

In a situation where the is oxidation, the viscosity of the oil will get heavier, ie you have a fresh sample with a viscosity of 96 SUS at 210 (its a 50 weight), under normal use (used oil history), it shears down to a 83 SUS.

If the oil is oxidized the viscosity would come in something higher than the original viscosity of 96 SUS.

NOW, another reason for coming in with a higher viscosity is the light ends of the oil blend are evaporating, leaving behind higher viscosity basestocks.
This would be more prevelant in oils that are 0W,5w, but a blender can use a heavy base stock and light basestock to achive the finished viscosity he was shooting for.

If the above were the case, you would first notice oil consumption.

I hope I answered your question.

Ken

Minx and Rage...you guys know your stuff!

:cool-smiley-027:

Minx obviously does but I am just a dumb layman asking as many questions that I can get away with within the limits of patience of you guys so as to learn enough that I do not screw up my engine. Thanks for your insight.

Bill

Ken,

Man that is some seriously insightful information. Thanks!!!

Just one follow up question. Specically, which additives would show the depletion you mention?

The viscosity is currently a problem for me to use as a reference since I have gas dilution going on which I am also trying to ID the cause/source.

95% of the time I am only cruising but I wish to know that I can run extended WOT if I want w/o doing any damaqe to my investment. I do not have the unlimited bucks that some do so I want to protect that investment with knowledge.

Thanks again for sharing your knowledge. That goes for everyone!!

Bill

Zinc, seeing how it is an anti-oxidant, would be almost gone in an oxidized oil.

For what it worth, the current API rating of SL addresses better oxidation control so current oil formulations are even better at controlling the oxidation issue than past oils.

In real life, it not a problem,we all change our oil waaaaay before we have to.

Thanks for the kind words.


Ken

OK watch the Zinc levels in used oil.

You are more that welcome for the kind words from my perspective. Your sharing of your obviously professional expertise (and time) is greatly appreciatred by this layman.

Bill

Amsoil 15W-50 racing Synthetic

I can not find a VOA anyone have one?

It looks promising.

Anyone?

What is the high end for allowable Bravo Drive lube temperature during WOT runs? I am using Redline Shock Proof Gear Lube.

ttt

mobil1 V-Twin
 

what are some of the best prices you guys have seen for Mobil1 V-Twin 20w-50? I found it a Auto-Barn online for $9.99/qt. free shipping over $50.00 I love this stuff.

About $10.50 - $10.60 / qt at O'Rielly Auto Parts Stores.

Merc Oil
 

Does anyone have a VOA on the Merc 25w/40 Syn blend oil?
My local Merc dealer does not use it. He uses Chevron Delo 15w40 for everything. I just want the very best for my 7.4mpi ski boat.

Mercruiser Service Bulletin from 1986.
 

Attached is supposedly a Mercruiser Service Bulletin from 1986 on acceptable oil temperatures in Mercruiser engines. Anyone know the history of this bulletin?

Yes it is a 1986 mercruiser SB. back then everything ran 140 degree t-stat and as a by product of combustion comes condensation so if you are using too big of an oil cooler or adding another one then most likely the oil will not burn off that condensation because you are not allowing the oil to get hot enough. Oil and water mix can happen with too cold of an oil operating temp.

One more thing cold oil does not flow very well or as fast as heated oil. One reason why some forms of race motors pre-heat their oil before start up. Best advice for a motor that sits for any lenth of time is use a pre-luber before start ups. Canton racing has one also masterlube.com has one and so does Amsoil but that would not top the list. As for the 1986 Mercruiser SB thats really some of the jist on it as stated above.

Rage, these temps are very good and the info Merc is suppling is also correct.

With a full group IV or V they can handle temps in excess of 300 F as a normal course of business.

That being said, the Service Bulleitin is on the money.

Ken

OK, then the only reason to worry about keeping full group IV or V oils at any temperature lower than ~300F+ is to keep the oil pressure at acceptable levels. In other words the engine may self destruck if the oil pressure gets too low do to elevated oil temperature but these oils will be fine. Got it. Thanks.

Rage, the viscosity gets to low because of the elevated temps, hence the pressure will drop. Remember all oils thin with heat.


With the thinner viscosity (due to high heat or fuel dilution) the oil film can't support the load of the application.

With thinner viscosity oils tighter bearing tolerences and higher pressures will solve the problem of "falling" thru the fluid flim.

Ken

Yep. I understand. I did not phrase my previous post well. I think you were saying that the full Grp IV and V oils will not be damaged from exposure to 300F+ oil temperatures and will recover from that temperature repeatedly and continue to perform essentially as if it had not happened. The heat related low oil viscosity versus engine viscosity requirements is a seperate issue. Correct?

One has to wonder what the oil pressure was in a 1986 Mercruiser engine with 1986 oils at 300F+ oil temperature.

Depends on the viscosity of the engine oil.

If you ran at those temps, a multi-vis 20w50 would THIN LESS, therefore be more viscous (thicker) than a straight 50.
The same would apply to 40vs10w 40 or and multi-grade vs the straight weight version of the 210 side.

It has nothing to do with the "year" of the lubricant.
Viscosity is viscosity, be it 1986 or 2009.

Ken

I thought I read on this thread that over the years the oil grade rating systems have become more and more performance stringent resulting in better and better performance out of the oils. That is what I ment thinking that this meant that an S_ grade in 1986 was not as good an oil as an SL is today. Is that incorrect?

Not sure if this is the right place to ask this, but, what oil does would be the best to run in the Mercury Racing 525. Also drive lube. I'm running Bravo X drives behind the 525's, so I want something that will help with the extra HP. I plan to change engine oil and drive lube every 25 hours. (That was the advice from the guy that installed the engines for me.

Yeah,
I posted it on another site.

If Mercury endorses 280F oil temperature as OK in their engines what is the resulting oil pressure that by default is also OK in Mercruiser engines running at 280F oil temperature?

The best performing oils from an anti wear standpoint were SG,SH. SJ and SL the levels of anti wear have dropped, however the oxidative stability of SL have improved over the SG,SH rated oils.

Your oil in 1986 had more anti wear than the current oils of today.

Ken

Can't answer that question, too many variables.

Oil viscosity, bearing clearance, different oil pump, etc.

Ken

I run a synthetic/petroleum blend motorcycle specfic oil 20w50 and a full synthetic 75w90, GL-5 gear oil in my outdrive.

I change every 20-25 hours.

Ken

Have been using Amsoil 20w-50 Series2000 for the last several years with excellent results. No oil analyisis,have had bearings out each year,look good. The above oil is no longer available, which should I go to: Amsoil Motorcycle 20w-50(MCV), Amsoil Motoroil 20w-50(ARO) or Amsoil Dominator15w-50(RD50)? HP500, now is 515cu Brodix heads etc. I run it hard, 20-25 hour oil changes. So what is it gonna be? Great thread by the way, beats working! to busy reading important stuff to go to meetings! robertjr

what's the latest and greatest on the 15-50 Mobil 1. I ran this in my engine before the rebuild, and the latest builder didn't think to highly of Mobil. I run it in both my vehicles and have no complaints. Is the Amsoil gonna be better than the silver cap or whatever the latest production is?

I hear 20 - 25 hour change interval a lot espically for the bigger HP motors. Is that seemingly short change interval mostly because of higher fuel contamination/dilution of the oil from such engines being tuned to run rich or because the oil temperature runs a lot lot hotter than 220-230F or because the oil temperature run a lot cooler than 212F or?

It's a schedule that I've kept for several years, ring end gaps are set up a little on the loose side,18-20 thousndths on the top ring I believe,bottom ring I couldn't tell youright now. Data is at the shop I run out of, aways from here so I may not be accurate.Get a little contamination on warm up! But when warm will run wide open for ever or till something beaks!!!! But what the hey! I'm a sick puppy!!!! usually at the end of summer anyway. But lasts a summer or two! I pull it down every year anyway! Jetted pretty close, choc brown plugs More reliability in the drive dpartment since using Severe gear 75w-90 So any opionions on the oil I asked about?

Personally I think it is number that has been picked as a safe number, perhaps it's a number that most boaters boat a year. I really don't know.

The auto industry was always a 3K oil change, now up to 15K according to oil monitoring programs in cars. The manufacture can't say a thing as they are the ones who built the software for the computer.


I would use oil analysis to make a determination of my oil if you have the opportunity to run 75-100 hrs/year. Pull a small sample and send it out. The lab should be able to say if the oil has more life in it or if you should change it. If you store for the off season, you should change it and then run it for 15-20 minutes before you fog the engine and store the boat.

As every one has said, oil is cheap insurance, change it, very true, but not always necessary.

Ken

Robert, I am sure that any of the oils you mention will work very well for the 20-25 hours of use. chances are there will be plenty of service life in the used oil.

Ken

15W-50 SilverCap is good stuff.

The M-1 V-Twin...Amsoil Racing 20W-50...Redline 20W-50...Motul 15W-50 would have a more hefty additive pack and base and would be worth considering if you run hard and race.

Amsoil Racing 20w-50 is no longer available,It's Gonna be Amsoil Dominator 15w-50, Amsoil"standard" 20w-50 or The Amsoil Motorcycle 20-50. So I realize I might have a short change interval, But out of these three, which has the best package of additives and such? Amsoil because have commercial acct. and great results although not "scientific". I want the best between these three. Cmon, you guys are the oil experts, I'm just an Electrical contractor!!!!................Roberjr

I was on the Amsoil website yesterday, it still shows the Racing 20W-50??
--------------------------------------------------------------------------------------
Nevermind, i was seeing things, it did go to a 15/50, wonder what they changed....

I have a mild build 502 MPI putting out approximately 500hp. It has had 8 hours of dyno time for break in and tuning on Brad Penn break in oil, and just under 2 hrs on the lake with the break in oil. I changed the oil at 10 hours and put in the Brad Penn semi-syn for winterization. At what hour mark would it be recommended to go the the full synthetic??

I do run the boat hard occasionally. But my wot runs are about 3 minutes, then i run out of room and need to throttle back usually.