Nomad Willy
Guru
kchase,
Re discussion please indicate type of oil.
Re discussion please indicate type of oil.
So, for the "traditionalists", in view of the facts please explain a good reason not to use synthetics since, in the long run, synthetics are cheaper.
The engines in our boat don't leak. But the crankcase ventilation is very crude....basically a pipe coming out the top of the valve cover that's aimed at the air filter on the turbo. I added a makeshift oil separator (some scotchbrite stuffed into the pipe), and a catch can hanging at the end of the vent pipe to recover the drips. But I'm pretty sure the whole arrangement has been pulling more than it's share of oil laden air out of the valve covers (rather than just venting). So this is a source of oil burn, as it gets sucked straight into the turbo and subsequently burned. I've been considering a Walker air/oil separator for years, but like others found it easy and inexpensive to just add oil. Anyway, I'm beginning to wonder if the synthetic oil might be less prone to being suspended in the crankcase and valve train mist, and therefor less likely to be pulled through that vent pipe and into the inlet side.
I should have a better sense of the reduction in oil consumption after run time builds on the engines. I probably should have waited to report on my findings before posting, but I was genuinely amazed when I checked the dip sticks.
Just to be clear about pour-ability of oil.....
from a marine engineer.... "Hmmmm, last time I looked "pour more freely" was the definition of lower viscosity or "thinner" oil"
From Princeton University - The definition of viscosity
"Viscosity is a measure of a fluid's resistance to flow. It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion."
Best to really understand the oil you chose than going by "rules of thumbs" or perception. No I am not saying use the oil your manufacturer recommended in a 5 year old or even 10 year old manual...but know what different types of oil is really going to do for YOUR engine, how you use it and how you wish to maintain it.
Just like extending oil intervals...I do oil analysis every 100 or so hoursof running. Not because I am concerned with oil wear or engine wear...I am concerned with oil dilution or contamination. Either can signal a major or stop an engine in far less time than engine wear. The oil change could take place AFTER the analysis...but the lag in reports are times well with my cruising style...so it works for me.
The 6CT 300 HP Cummins in my charter boat gets run hard. Short warm up followed by 5 minutes of slow operation, then up to 80% for hours. When I get on site, it's slow operation for ten minutes, then shut down. The return trip is the same. First 50 hours uses less than one quart in 50 hours. Somewhere between 50 and 100 hours oil consumption goes to one quart in 6 hours. Oil is black by 25 hours. IMO, the soot levels drive a lot of this. IMO, the soot is likely there regardless of oil type. So, I think it's more beneficial to change the oil in this application every 50 hours. Really don't feel that running 3 times as long with 3 times as much soot is a good idea. Oil analysis with each oil change says everything is good.
My Dodge pickup with a Cummins 6BT 220 HP runs on average at 25% of capacity. Engine has 469,000 miles (9,400 hours) on it and uses less than a quart of oil between oil changes (every 5,000 miles). Oil is amber at oil changes. While oil analysis is still good at 5,000 miles, I don't think extending oil changes to 15,000 miles to justify the use of synthetic makes sense. Feel that additional oil analysis would be required to make sure the additives remain at acceptable levels between oil changes. Also feel that less than 2 oil changes per year is less desirable than 4 to 6.
Ted
An oil's viscosity rating, 15W-40 for example, only tells part of the story. The 15W number is the rating at 104 degrees. The 40 number is the rating at 212 degrees. At lower temperatures, synthetics do, in fact, pour more freely than do conventional oils despite the nominal SAE rating. It has to do with the molecular structure of the oil. Take a look at the YouTube video I attached. It was a demo performed by Shell Oil. It says all you need to know. Last I knew Shell sells synthetics and conventional so this demo holds no bias. There is a place for both types. Now don't go crazy when you see that the test was done at a temp of -40 degrees. There is a significant difference in pour characteristic at all cold temps. That is why synthetics are better at mitigating cold start-up wear at any temperature as they flow to the internals faster than synthetics. Now, the old wives tale is that 90% of engine wear occurs at start-up and warm-up. If one accepts that synthetics flow better than conventional at any temperature, one must conclude that any engine wil last longer using synthetics.
There will always be non-believers despite science and facts. There is no such thing as global warming/climate change, is there?
After reading the Cox Engineering link I ask;
Does any marine engine manufacturer recommend using synthetic lube oil?
Ski wrote on post #27,
“Going with syn does not automatically mean you can extend change intervals. Crud added to good oil still ends up being cruddy oil. Sampling is what tells the story. Even dino oil can go well beyond spec change intervals, and it has more to do with engine duty cycle and other stuff, not so much whether dino or syn.”
It would seem to me the only way to get rid of soot and particulate (grit) is to drain the oil when the engine is hot and most solids are in suspension.
How much abrasive wear is caused by this “dirt”?
It would seem to me the only way to get rid of soot and particulate (grit) is to drain the oil when the engine is hot and most solids are in suspension.
Good thread. A few early AM musings -
On Cat powered large dirt moving fleet operations I'm familiar with non synthetics rule. Why? Warranties and cost. As mentioned by Ski and others, synthetic oils don't automatically carry a longer run time.
Cat warranties, a very big deal, require the same oil change intervals. For large fleets, this translates to an increased lube cost of many hundreds of thousands of dollars per year to use synthetics. Hardly makes sense except for those extremely cold operations where synthetics can have the advantage for cold start times.
If the oil analysis on your charter boat comes back "good for continued use" why do you not believe your oil analysis report? I do understand that looking at that black oil is disconcerting but the oil analyses do not lie. However, I have sometimes changed the oil on my Chevy Duramax "just because" even though I really do not need to do that. I did that once at 900 hours even though the test showed no need to do so. That truck still starts and runs as the the I bought it 17 years ago and 292,000 miles.
I've actually had opposite results on syn oil that was put in my performance car engine 383 full roller used a bit of oil with syn and none with dino.
Pretty much all new cars are coming full syn now, that 0w number always gives me pause when I pick it up...
CatalinaJack said:An oil's viscosity rating, 15W-40 for example, only tells part of the story. The 15W number is the rating at 104 degrees. The 40 number is the rating at 212 degrees.
NomadWilly said:And on the same subject how long does the viscosity improver last. That is how long does the effects of the VI last. 10w30 is or starts out as 10 weight oil and gets stabilized so it has the viscosity of 10w oil when cold and 30w when hot. So if the VI looses it’s affect the oil is 10 weight .. not 30w.
Clearing up a mistatement repeated above might help get at the viscosity questions still open.
Neither of those statements are correct. "15w" is the "winter" rating of the oil - "w" in a multi-grade oil refers to it's "winter" characteristics. This is a measure of pumpability/cranking viscosity at various winter temperatures. "15w" means it meets the spec (3,500cP) at -15c. Same for "20w", "10w," "5w". The "5" step increments are inverse around the -15c. Like this:
0w -30C (-22F)
5w -25C (-13F)
10w -20C (-4F)
15w -15C (5F)
20w -10C (14F)
25w -5C (23F)
30w 0C (32F)
The warm rating, "30," "40" etc. is viscosity taken at 104F/40C, not 212F.
The high temp rating is, indeed, measured at 212F. I refer you to Wikipedia https://en.wikipedia.org/wiki/Motor_oil.
"A single-grade engine oil, as defined by SAE J300, cannot use a polymeric viscosity index improver (VII, also viscosity modifier, VM) additive. SAE J300 has established eleven viscosity grades, of which six are considered Winter-grades and given a W designation. The 11 viscosity grades are 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60. These numbers are often referred to as the "weight" of a motor oil, and single-grade motor oils are often called "straight-weight" oils. For single winter grade oils, the dynamic viscosity is measured at different cold temperatures, specified in J300 depending on the viscosity grade, in units of mPa·s, or the equivalent older non-SI units, centipoise (abbreviated cP), using two different test methods. They are the cold-cranking simulator (ASTM D5293) and the mini-rotary viscometer (ASTM D4684). Based on the coldest temperature the oil passes at, that oil is graded as SAE viscosity grade 0W, 5W, 10W, 15W, 20W, or 25W. The lower the viscosity grade, the lower the temperature the oil can pass. For example, if an oil passes at the specifications for 10W and 5W, but fails for 0W, then that oil must be labeled as an SAE 5W. That oil cannot be labeled as either 0W or 10W.
For single non-winter grade oils, the kinematic viscosity is measured at a temperature of 100 °C (212 °F) in units of mm2/s (millimeter squared per second) or the equivalent older non-SI units, centistokes (abbreviated cSt). Based on the range of viscosity the oil falls in at that temperature, the oil is graded as SAE viscosity grade 20, 30, 40, 50, or 60."
In the chart above, the oil meets the winter rating and then VII - viscosity index improvers - are added to artificially thicken the oil. They are not durable, do not lubricate, and for oils with a wide viscosity spread (5w-40, e.g.), can be a large part of the oil by weight and volume.
if you take good look a the values above, you can see that unless you routinely start your engine with the engine room below freezing, you are wasting valuable lubrication capability by not running straight-weight oil. You are also gaining no "cold start" benefits.
Nomad Willy asked above about VII's being rubber. In the past, they were. A petroleum engineer explained to a group of us that in fact, in the 80s, they actually recycled tennis shoe soles by grinding them to fine dust and adding them to oil. Nowadays, they are far more highly engineered synthetic molecules, but still the same principal.
This is pretty engine-specific. How hot the oil runs on average and in unique spots, how much shear is experienced in different sections of the engine (internal gears, etc.), total oil volume, presence or not of a turbo, etc. all effect this. Some engines are really easy on oil, and others can chew up the VIIs in short order because of design characteristics.
Gas engines I know better; so let me give an example there - there are gas engines on the road that will destroy an average 5w-30 motor oil in 5 to 6k miles. The same engines can run happily 10k miles on higher quality 10w-30 synthetic (Yes I'm looking at you, Toyota 1mz-fe V6).