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Reepicheep
| | Posted on Wednesday, July 06, 2011 - 03:55 pm: | 
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I don't want to buy Amsoil because it is a miracle oil that does something other synthetics can't.
I want to buy it because it is a high quality synthetic in the weight I want for a competitive price and because they support Erik Buell Racing.
It used to be you could get Castrol Syntec 20w50 for a lot less ($4.50 a quart or something), but that seems to have dried up, and all the full synthetics are $7-$9 now. I was always a little suspicious of the Castrol Syntec anyway... ever since I used their 0w50 and it caused massive oil consumption on my 9sx. Like maybe their defnition of "synthetic" is a little more creative than others. |
Hughlysses
| | Posted on Wednesday, July 06, 2011 - 04:18 pm: |
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Like maybe their definition of "synthetic" is a little more creative than others.
When Castrol first introduced their "synthetic" oil, Mobil actually took them to task for false advertising. The complaint was thrown out because there was no legal definition for "synthetic" oil. Here's one take on the story from an Amsoil website: http://www.syntheticsbestoil.com/mobil.htm |
Electraglider_1997
| | Posted on Wednesday, July 06, 2011 - 04:36 pm: |
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Blake,
I used the word nonexistent because straight 60W is super thick at ambient temp according to what I learned in Bobistheoilguy Motor Oil University. Just look at the table on this link to see how thick straight 30W is at 75F and you can just imagine how bad the flow at startup would be with 60W. Reading through Motor Oil U is very easy and informative. Written by a surgeon/biochemist that has a pathological interest in engine lubrication.
http://www.bobistheoilguy.com/motor-oil-103/ |
Electraglider_1997
| | Posted on Wednesday, July 06, 2011 - 04:39 pm: |
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What is very interesting is that dino oils start thin and add thickeners and synthetics start at the prescribed weight and modify the exact opposite way. All explained way better in Motor Oil U. |
Etennuly
| | Posted on Wednesday, July 06, 2011 - 04:48 pm: |
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Thicker oil has similar physical characteristics to thinner oil. It gets thinner as it gets hotter. Thicker oil has larger molecules that get tar or wax like when colder, but that is not in the equation as we are not trying to run it in the colder temperatures.
IMHO larger molecules will move less rapidly, flowing slower will allow for them to carry more heat from the engine to the oil cooler where it will allow for better heat transfer than that thinner oil with very fast moving small molecules.
It is all about what you want the oil to do for your engine. In the race bike Blake mentioned the thin oil has a benefit to less internal drag, they were probably not running two hundred laps with the airflow choked off from the heads where the top end might be exposed to overheating.
The engine is making growling and rattling noises because of large clearances causing metallic impacts or sliding impacts. Thicker(larger molecular) oil will cushion these impacts not unlike saw dust on a smaller scale. Thinner oils will be very slippery but allow the impacts without cushioning.
This is the theory that could have led to Hugh's bearing failure. The clearance of the bearing's fit allow for the ball to lift from it's race. Thick oil would act as a cushion (quieter), super slippery thin oil could do as a mechanic suggested, let the bearing's ball skip as it was reintroduced to the race, causing scratching on the microscopic level of it's surface, thousands of times later leading to potential failure.
Again, this is IMHO. I do have a little background in building race engines for my dirt track cars and street cars. I also spent a few years in vocational classrooms and in the automotive business in sales promotional classes for things like oils and mechanical parts, and factory tech schools for dealerships that I worked in over the years.....but I don't let that crap interfere with my judgment of this subject. But I have stayed in a Holiday Inn Express. |
Blake
| | Posted on Thursday, July 07, 2011 - 02:15 pm: |
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Craig,
>>> you can just imagine how bad the flow at startup would be with 60W.
But as I questioned, how can that happen with a positive displacement oil pump? For ever revolution of the pump, it takes in a set volume of oil and ejects it out the output port. There is likely some flow reduction due to elasticity effects of the pump body, oil lines, etcetera, but I don't see it being drastic. It's like an electric circuit with a small capacitor, voltage being analogous to pressure and current being analogous to flow rate.
Conventional oil is modified with additives called viscosity modifiers, molecules that increase in size with increasing temperature. They don't thicken the viscosity though. They just help prevent the oil as a solution from losing too much viscosity with increasing temperature.
Vern,
I don't see how with a positive displacement oil pump running at a steady state rate, oil flow in the heads will be slower for a higher viscosity grade oil than for a low one. But most notably, higher flow rate means better cooling in virtually all cases of conductive and convective heat transfer. Lower flow rate almost always means less heat would be removed. The flow rates being nearly equal at operating temperature (a 20W50 has virtually the same viscosity at 300oF as does a straight 60 weight engine oil), the only effect you are introducing is higher pumping pressures at lower operating temperatures, yes even at 80F.
The table in the owner's manual is primarily concerned with minimum temperatures, and that we don't run too viscous of an oil in lower operating temperatures. The table is not making recommendations based on maximum ambient conditions.
If the airflow is choked off to the heads, the absolute best oil to have is a synthetic, as it will not turn to carbon as soon as a conventional oil will.
If bearing clearances are too great, that is a problem that a higher viscosity oil may marginally help, but it is a problem that no new motorcycle should have. Basically you end up with just a few rollers carrying the load that was meant to be shared by a lot more.
To have a sliding "impacts" the oil film would have to have broken down. Again, at elevated operating temperatures a 20W50 engine oil will have darn near the same viscosity as a straight 60 weight engine oil, so I don't see that as a plausible explanation for Hugh's bearing failure. My experience is that most noisy Harley engines are noisy due to loose tolerances in the valvetrain, lifters than aren't pumping up like they should.
The benefit of a conventional straight grade engine oil compared to a multi-vis grade conventional oil that it's viscosity won't degrade with high temperature as drastically. So if it's warm enough, and you don't care to run synthetic, the straight grade conventional oil might provide better protection over the life of the oil than a multi-vis conventional oil.
>>> It is all about what you want the oil to do for your engine.
 Lubricate, cool, clean, and protect against corrosion it. What else is there? |
Blake
| | Posted on Thursday, July 07, 2011 - 02:20 pm: |
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One thing to note is that while the oil pump flow may remain effective even for high viscosity oil at lower temperatures, the flow to some portions of the engine may suffer as the oil will seek the path of least resistance. So maybe the oil flowing to the valvetrain may be diminished since the paths to the bottom end and heads is less restrictive, or vice versa. I don't know the specifics, just pointing out that there could be such an effect and likely is one. That could make having too viscous an oil at lower temperatures a very bad scene. This is likely why the owner's manuals are careful to specify oil grades based on the minimum ambient temperature.
(Message edited by Blake on July 07, 2011) |
Etennuly
| | Posted on Thursday, July 07, 2011 - 05:38 pm: |
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When you introduce an air finned oil cooler (much like a radiator) the oil can flow through fast enough that it does not effectively transfer heat. Such is the case with a radiator in a cooling system. Take out the thermostat and almost always you will have run-away coolant temperatures. The coolant must flow through the vanes of the cooler slow enough to make use of the air flow through the fins to transfer heat.
I still contend that the thinner oil is flowing faster throughout the system and not picking up as much heat in the heads nor transferring it out through the cooler.
I don't know if you have ever changed oil when it is truly hot, but full synthetic oil is thinner than water at that point. Non syn still will have some viscosity, especially 60W.
This is an oil thread.....I am right............................................. .................................................. ...........  ..................................as is everyone else! |
Mark_weiss
| | Posted on Thursday, July 07, 2011 - 06:21 pm: |
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From racing background, thinner oil is better for cooling. Not because the oil flows more freely or has better heat carrying characteristics, but because lower viscosity oil forms a thinner insulating layer between parts.
Although oil does carry heat fairly well, it is still an insulator. Closer proximity between pistons & cylinders, etc. means better heat transfer away from core parts. |
Jlnance
| | Posted on Friday, July 08, 2011 - 07:39 am: |
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But as I questioned, how can that happen with a positive displacement oil pump?
Cavitation?
Positive displacement pumps will squirt out everything they suck in. There isn't a way to guarantee they will be able to suck anything in. The best they can do is pull a vacuum on the input line and take the flow that results.
I'm just answering because I enjoy these discussions. I've no idea if this is a problem with the Buell oil pump. |
Pontlee77
| | Posted on Friday, July 08, 2011 - 08:03 am: |
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Here in Spain the first oil change was to the screaming eagle syn III or something like that, the bike was like drinking it, so when the 2 year warantee expired I used Spectro mineral that was quite good until i found out i could buy Castrol Actevo 20-50 (mineral) at a great price, since then (20.000 miles) I carry on using the castrol mineral, bike runs great, doesen't use up any oil, and it makes life and care of the uly easier. |
Electraglider_1997
| | Posted on Friday, July 08, 2011 - 08:12 am: |
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Blake,
I've been trying to find the answer to your question and can't exactly say I have one yet or will find one but here are some things I've thought of. 75 degree F 60W, according to Motor oil U won't even go through the proper channel of the oil filter, it will bypass until it gets thin enough. Another thing is that the oil flow of 60W, while cold, probably won't shoot through the orifice that sprays the underside of the piston. Every place that oil has to flow until it heats up will be under very high pressure because it just won't move like a thinner oil will. High pressure isn't necessarily mean better oil lubrication. Only so much pressure is wanted and called for in the service manual. I've got the 07 service manual in hand from answering another question elsewhere and I see on page 3-3 that a new oil pump output is 7-12 psi at 1000 rpm and 10-17 psi at 2500 rpm. Even our constant volume pump has a fairly large operating range since a pressure range certainly correlates to a volume range.
A weak battery will have a much easier time turning over the starter with a lower viscosity oil than a straight 60 wgt oil when the engine is cold. Being focused on what the pump will or won't do doesn't account for what goes on in the rest of the engine, at least that is what I think. I'm only trying to reason through this with what I learned in Motor Oil U.  |
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