Shell Rotella T6, 5w40, 135 hours, Mercruiser 7.4

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May 21, 2012
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Fort Lauderdale, FL
Metals (ppm)
Iron (Fe) 41
Chromium (Cr) 1
Lead (Pb) 23
Copper (Cu) 33
Tin (Sn) 1
Aluminium (Al) 4
Nickel (Ni) Silver (Ag) Titanium (Ti) Vanadium (V) Contaminants (ppm)
Silicon (Si) 11
Sodium (Na) 41
Potassium (K) 19
Additives (ppm)
Magnesium (Mg) 1043
Calcium (Ca) 1080
Barium (Ba) Phosphorus (P) 1062
Zinc (Zn) 1340
Molybdenum (Mo) 65
Boron (B) 38
Contaminants
Water (%) 0.15
Coolant No
Physical Tests
Viscosity (cSt 100C) N/A
Physical / Chemical
Base Number (mgKOH/g) 6.2

Viscosity could not be tested due to water contamination. My guess is the crankcase takes on water through condensation from sitting. That these engines have to run a 160° thermostat and an oil cooler, and have no PCV can't be helping things. I'm livid. I wanted to know if it sheared.

The K&N flame arrestor is obviously working out better than the stupid metal grille that is the stock flame arrestor. Only product I'll buy from them.
 
These results seem ok, but I would worry a little with the lead and iron. Those seem a little high for the hours run.
Most of us Merc guys think the big blocks need a thick oil that is very sheer resistant to keep those heavy cranks etc. from damaging. 15w40 and 15w50 have always been my choices. You have run one that I was always curious about, but never gutsy enough to try. Do you have other analysis to compare it against?
 
I'm running the venerable VR1 20/50 synthetic now. I'm going to pull a 50 hour analysis out of her tomorrow to see what I get. Hopefully there's no water in the sample. I'm going to let her get up to temp and sit there for 30 min before I pull the sample out.

I moved away from the RT6 because it's known to shear pretty easily in motorcycles. Boat engines seem to do just as good a job, if not worse. VR1 is notoriously shear resistant over an OCI, so I'm curious to see how it pans out over 50 and 100 hours.
 
What is your sump capacity? Because depending on that, 100 hours seems excessive and equivalent to 10,000
road miles at the working rate of a boat engine.
I just changed out 11 liters of oil in my DuraMax at 108 hours which was 5,600 miles.

Your lead could be from a fuel additive.
 
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That's a lot of hours on that oil, doesn't Merc spec 50 or 100?

If the pan is stock those big blocks only have little sumps.
 
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This one takes 9 quarts. Stock pan, external side mount oil cooler, riser mounted remote oil filter, and oversized FU XG5. Thankfully doesn't consume any oil either.

Mercruiser says 100 hours with syn. Universal averages for a 48 hour run is 28ppm Iron, 7ppm for lead, and 32ppm for copper (my guess is the oil coolers shed alot.)

That makes the wear metals well below average for a 135 hour run, and even the lead not so bad. The lead is likely from the carb cleaner I put into the carb before coming to the conclusion it needed to be rebuilt.

I was happy to see no heavy fuel contamination, because these nasty Weber carbs notoriously run pig rich at idle/low RPM's. I always seem to pull blackened plugs out, even with fine tuning. The new NGK Iridium seem to care nothing for it, because the electrodes stay shiny clean.

TBN of 6.7 shows the T6 was not nearly done. I just wish I knew if it sheared.

Interested to see how VR1 stacks up.
 
No need for a 5w-40 in FL, especially in a marine engine. 15w-40 is fine, and Mercruiser's 25w-40 works fine as well.

Had the engine been sitting a while when you pulled the sample? Next time pull a hot sample.

How many hours on the engine?
 
Gotta agree with Paul. I think any 5/40 in a marine engine is not the best choice. There is a reason for Merc's 25/40 oil. I am curious if you heard anymore valve train chatter using it. Assume not if you didn't mention it.

If you had to use an HEDO I think you would be better off with a non syn 15/40.
The VR1 will be a nice step up in the right direction.To bad you wont be able to compare the VIS but I bet the wear numbers will be lower. The VIS will hold up better in any conv or syn 20/50 over a 5/40.

Its hard to get marine oil good and hot with the low thermostat, I guess you are aware it takes way longer then just the water temp gauge shows. Before you take a sample REALLY give the engine a long run.
 
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This engine (port) has never even thought of clattering. It has 1781 hours on it and runs like a sewing machine.

She wasnt sitting all that long. Maybe 2 weeks then ran her up for 20 min. Next time I'm going to run it a while at high idle to get a sample. Be live me I know how long it takes for the oil to heat up. I have closed cooling on both engines (engine and manifolds), so I can get away with a 180° thermostat without worrying about salt deposits. But having an unregulated oil cooler constantly channeling fresh cool water does not help. Heck, it might be better just to rag on her for an hour and sample. More fun that way.

I've always believed that the Mercruiser oil spec was more about what shear monsters these engines are than anything. The OCI'S definitely reflect that. My lifts have OCI'S of 200 hours. Mercruiser calls for a 50 hour OCI on the same GM 4.3, using the same grade oil oil.

Understandable since these engines are hauling a heavy load, uphill, in second gear.
 
What makes these engines "shear monsters" compared to a diesel in an industrial or agricultural application?

e.g. Take a look at John Deere's oil test, they run an engine at maximum load for 500 hours.
 
They run their engines at 100% of their industrial HP rating.
An example of that would be a locomotive engine operating at 4,400 hp for thousands of hours at 1050 rpm. Chip that monster and it will put out 15,000 hp.
A BBC industrial engine might, on a good day, put out a continuous 200 hp driving an irrigation pump.
 
Originally Posted By: DoubleWasp
This engine (port) has never even thought of clattering. It has 1781 hours on it and runs like a sewing machine.

She wasnt sitting all that long. Maybe 2 weeks then ran her up for 20 min. Next time I'm going to run it a while at high idle to get a sample. Be live me I know how long it takes for the oil to heat up. I have closed cooling on both engines (engine and manifolds), so I can get away with a 180° thermostat without worrying about salt deposits. But having an unregulated oil cooler constantly channeling fresh cool water does not help. Heck, it might be better just to rag on her for an hour and sample. More fun that way.

I've always believed that the Mercruiser oil spec was more about what shear monsters these engines are than anything. The OCI'S definitely reflect that. My lifts have OCI'S of 200 hours. Mercruiser calls for a 50 hour OCI on the same GM 4.3, using the same grade oil oil.

Understandable since these engines are hauling a heavy load, uphill, in second gear.
I spent most of my life working at a Clark lift dealer and forklift engines are governed at around 2100 to 2300 depending on the engine. Hardly loaded.A boat engine can run for hours at max rpms in certain applications.
 
Originally Posted By: used_0il
They run their engines at 100% of their industrial HP rating.
An example of that would be a locomotive engine operating at 4,400 hp for thousands of hours at 1050 rpm. Chip that monster and it will put out 15,000 hp.
A BBC industrial engine might, on a good day, put out a continuous 200 hp driving an irrigation pump.


Marine engines are far more HP dense than engines used in other applications. Also they are always running at 80% of max load, they never get a break.

The locomotive diesel is massive and very low stressed. In a marine application it probably could put out 15k HP but it would do it for a far shorter operating life. In the train it might run 10k or 20k hours before major work is done, but at 15k HP and with the characteristics of marine operation the service life might be like 2k-4k hours or even less.

In the big Cat equipment for example their V12's only put out around 700hp, in marine applications they are 2 or 3 times that at least if not more. Also in the equipment they are not running at max load, more like 30%ish, and the rpm's are kept down. On say a Viking 72 they are running at least 80% if not 100% if the owner is in a hurry. That's a massive amount of stress being placed on the motor.

Going back to that, Merc recommends an oil for their engines in a different grade simply because they are used differently.
 
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If I were still running a gasoline marine engine I would seriously consider a 30 wt HDEO simply for shear resistance. The last gas marine engine I had was a 460 and it had nothing but 30 wt its entire life I ran it for over 3,000 hrs, sold it and its still in another boat running.

In marine applications it doesn't take as long as one may think to warm up the oil, even with an oil cooler, thats why theres one there. My 460 was a Chrysler marine conversion which I bought new and installed it in a commercial application, it came without an engine oil cooler!! This engine was raw water cooled and would run, depending on destination, for hours at a time. I never ran it over 3,000 rpm as I tried to stay out of the 4 barrel.

That engine was replaced with a Deere 6076, same application except the diesel gets run at governed rpm (2,200) and yes it gets 500 hr. OC per manufacturer vs. 50-100 hr OC for gasoline. Boats aren't really a high stress application, as long as they're propped correctly, high rpm's doesn't mean high stress. Running in a heavy following sea would be the worst case for high stress.
 
To see shear resistance in a SAE30, look at the UOA I posted about 6 months ago. DuraMax in the UOA Diesel threads.
 
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With as many hours as the OP logs, I would go with an xW-50. A lot of the go-fast folks have reported using M1 20W-50 Motorcycle oil with good success. It is kind of pricey though. Personally, I use the cheapest synthetic xW-50 I can find in my SBC Volvo Penta.
 
There's no doubt that the rpms are the factor is making these engines the shear monsters that they are. Otherwise, they're just regular GM 454's.

I am running VR1 20/50 now, which has actually proven to be rock solid stable, even in extended runs in Harley engines that eat oil viscosity for breakfast.

48 hour UOA for that coming very soon.
 
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