I found this online and don't see why they would recommend Diesel oil over those oils made and sold as motorcycle specific oils. Everything you wanted to know about oil can be found here:
http://www.petro-canada.ca/pdfs/englube.pdf
The Codes are listed here starting about page 34
"S" – SPARK IGNITION (Gasoline, Propane, CNG)
The second letter designated the type and year of the additives
In general The higher the code, the newer the oil. It is generally OK to use a higher letter, however, some oils had detergents while others didn't. If you have an older vehicle that was not designed to handle detergents (to reduce deposits) it may be harmeful to add an oil with detergent in it. Different additives could have a detrimental effect the different materials used for gaskets and seals.
Exerpts from the link:
Standards SA to SF are considered obsolete. The current standard is backservicable to these standards.
SG = Service typical of gasoline engines in passenger cars, vans, and light trucks beginning with the 1989 model year
SH = 1994 provides improved control of engine deposits, oxidation and engine wear relative to oils developed for previous categories. Oils meeting API Service Classification SH may be used to replace SG, SG/CC, SF, SF/CC and SE are recommended. (obsolete)
SJ = 1997 SJ may be used where API Service Classifications SH
and earlier have been recommended.
SL = 2001 Service typical of gasoline engines in passenger cars, sport utility vehicles,
vans and light trucks effective July 1, 2001. In addition to a general improvement
in quality, this new standard aims specifically to improve oil volatility,
SM = 2004 In addition to a general improvement in quality, this new standard aims specifically to improve oil volatility, oil life, fuel economy and emissions system compatibility. Oils meeting API Service
Classification SM may be used where API Service Classifications SL and earlier have been recommended.
"C" – COMPRESSION IGNITION (Diesel)
CA FOR DIESEL ENGINE SERVICE 1940's and 1950's
Service typical of diesel engines operated in mild to moderate duty with high
quality fuels and occasionally has included gasoline engines in mild service.
CB FOR DIESEL ENGINE SERVICE 1949.
mild to moderate duty, but with lower quality fuels which necessitate more protection from wear and deposits.
CC FOR DIESEL ENGINE SERVICE 1961
Service typical of certain naturally aspirated, turbo-charged or supercharged
diesel engines operated in moderate to severe duty service and certain heavy-duty
gasoline engines. Oils designed for this service provide protection from
high temperature deposits and bearing corrosion in these diesel engines and
also from rust, corrosion and low-temperature deposits in gasoline engines.
CD FOR DIESEL ENGINE SERVICE 1955
Service typical of certain naturally aspirated, turbocharged or supercharged
diesel engines where highly effective control of wear and deposits is vital, or
when using fuels of a wide quality range including high sulfur fuels. Oils
provide protection from bearing corrosion and from high-temperature deposits in these diesel engines.
CD-II FOR FOR SEVERE DUTY 2-STROKE
Service typical of 2-stroke cycle diesel engines requiring highly effective
control over wear and deposits. Oils designed for this service also meet all
performance requirements of API Service Category CD. (obsolete)
CE = 1983 DIESEL ENGINE SERVICE - certain turbocharged or supercharged heavy-duty diesel engines operated under both low speed high load and high speed high load conditions. Oils designed for this service must also meet the requirements of the API Engine Service Categories CC and CD.
CF = 1994 OFF-ROAD INDIRECT INJECTED DIESEL ENGINE SERVICE
off-road indirect injected diesel engines and other diesel engines that use a broad range of fuel types
including those using fuel with higher sulphur content, for example, over 0.5% wt. Effective control of piston deposits, wear and corrosion of copper-containing bearings is essential for these engines which may be naturally aspirated, turbocharged or supercharged. Oils designated for this service may also be
used when API Service Category CD is recommended.
CF-2 FOR 1994 SEVERE DUTY 2-STROKE CYCLE DIESEL ENGINE SERVICE
two-stroke cycle engines requiring highly effective control over cylinder and ring-face scuffing and
deposits. - may also be used when API Service Category CD-II is recommended. These oils do not necessarily meet the requirements of CF or CF-4 unless the oils have specifically met the performance requirements of these categories.
CF-4 FOR 1991 DIESEL ENGINE SERVICE
Service typical of severe duty turbocharged, 4-stroke cycle diesel engines, particularly late models designed to give lower emissions. These engines are usually found in on-highway, heavy duty truck applications. API CF-4 oils exceed the requirements of CE category oils and can be used in place of
earlier CC, CD and CE oils.
CG-4 FOR 1994 SEVERE DUTY DIESEL ENGINE SERVICE
For use in high speed, four-stroke cycle diesel engines used in highway and off-road applications where the fuel sulphur may vary from less than 0.05 percent to less than 0.5 percent by weight. CG-4 oils provide effective control over high temperature piston deposits, wear, corrosion, foaming, oxidation
stability and soot accumulation. These oils are especially effective in engines designed to meet 1994 emission standards and may also be used in engines requiring API Service Categories CD, CE and CF-4.
CH-4 FOR 1999 SEVERE DUTY DIESEL ENGINE SERVICE
For use in high speed, four-stroke cycle diesel engines used in highway and off-road applications, where the fuel contents range from less than 0.05% to less than 0.5% by weight. CH-4 oils provide superior control over high temperature piston deposits, wear, corrosion, foaming, oxidation stability and
soot accumulation. These oils have been specifically formulated for engines designed to meet November 1998 EPA emission standards and may be used where API CD, CE, CF-4 and CG-4 oils are required. Oils designated for this service have been available since 1999.
CI-4 (CI-4 PLUS) FOR 2002 SEVERE DUTY DIESEL ENGINE SERVICE
For use in high speed, four-stroke cycle diesel engines used in highway and off-road applications where fuel sulphur contents range from less than 0.05% to less than 0.5% by weight. This new category is designed to cope with stringent environmental emissions legislation and increased engine severity
caused by Exhaust Gas Recirculation (EGR). Oils designated for this service are currently available from Petro-Canada and may also be used where API CD, CE, CF-4, CG-4 and CH-4 oils are required.
CJ-4 FOR 2007 SEVERE DUTY DIESEL ENGINE SERVICE
For use in high-speed four-stroke cycle diesel engines designed to meet 2007 model year on-highway exhaust emission standards as well as for previous model years. These oils are compounded for use in all applications with diesel fuels ranging in sulphur content up to 500 ppm (0.05% by weight). However, the use of these oils with greater than 15 ppm (0.0015% by weight) sulphur fuel may impact exhaust after treatment system durability and/or oil drain interval.
Can anyone explain why Harley recommends a diesel
- Thread starter BigCahuna
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The link doesn't work. But the "S" in the ratings does not stand for "spark" ignition, and the "C" does not stand for "compression" ignition. That's a very common misconception. They actually stand for "service grade" and "commercial grade," respectively.
Most diesel oil/heavy duty engine oil is dual rated for use in both gas/diesel engines.
I believe Harley doesn't care so much about using a diesel oil, they just want you to use a heavy duty engine oil.
I couldn't get the link to work either. Try this one:
http://www.oilspecifications.org/api_eolcs.php
Here's one that has a side by side comparison of HDEO:
http://www.pqiamerica.com/June%202014/consolidated%20HDEO%202015.html
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To bring some of you up to speed about Harley oil here's some interesting info. While Harley's oil that's sold thru their dealership network is highly recommended by Harley for use in their motorcycles,does not carry an API symbol. They just say it's the oil to use and charge premium $$$ for it. That also goes for about every other motorcycle specific oil sold. Amsoil, Mobil 1 V-Twin oil, Valvoline ect. They say it meets a SG spec and is GL-1 rated, but only they test it. So why does Harley recommend an diesel oil that carries a higher spec then their own oil, when there are oils available that have proven to be of better quality or at the very least, as good as their own?. Soot and combustion gases have never been a issue with Harley's like they are with diesel motors, so why would this oil be preferred over any 20/50 wt with a SG rating?.,,
I think the reasoning is this.
I have seen some Motorcycle specific oils...Kendall's for instance that are EXCEPTIONALLY weak on anti wear additives. Maybe Harley wants you to use a diesel rated oil because they typically have higher anti wear additives packages over their "s rated" cousins.
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I believe it's all about marketing. Why would Harley recommend a 20/50 oil from a different manufacturer? That would cut into their market share. Try and find a readily available 20/50 that meets the latest HDEO spec. They are few and far between. Since most people want to run a 20/50 in their Harley and Harley recommends their 20/50 first and then a HDEO 15/40 second, I believe most people will opt for Harley oil. Unlike PCMO and HDEO, there is no spec for "MC specific" oil. So Harley recommends their 20/50. It's all about marketing and the bottom line. I'm sure if it wasn't working out for them, they would change. I guess they figure if it ain't broke, don't fix it.
Well most all other makers recommend an oil. Triumph recommends I use 10w50 Castrol Racing 4T. But it also says I can use any oil 10w40 or 10w50 that meets SG or higher and is JASO MA rated. My old Yamaha recommended Yamalube. Everyone tries to push their own oil, or their partners oil(as in the case with Triumph)
Harley might be crafty in the sense they know there is a very limited 50 weight family of C spec oils, so there are fewer alternatives to Harley oil if you want to keep your warranty.
Originally Posted By: exranger06
The link doesn't work. But the "S" in the ratings does not stand for "spark" ignition, and the "C" does not stand for "compression" ignition. That's a very common misconception. They actually stand for "service grade" and "commercial grade," respectively.
Here are the 13 Diesel Oils that were tested by 540Rat. And they are
ranked in the order of their “Load Carrying Capacity/Film Strength”
values:
1. RED LINE, 15W40 Diesel Oil, synthetic, API CJ-4/CI-4 PLUS/CI-4/CF/CH-4/CF-4/SM/SL/SH/EO-O
“Load Carrying Capacity/Film Strength” = 85,663 psi
zinc = 1615 ppm
phos = 1551 ppm
moly = 173 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 2999 ppm
TBN = 8.3
The onset of thermal breakdown is approximately 285*
2. ROYAL PURPLE, 15W40 Diesel Oil, synthetic, API CJ-4 /SM, CI-4 PLUS, CH-4, CI-4
“Load Carrying Capacity/Film Strength” = 76,997 psi
zinc = TBD
phos = TBD
moly = TBD
total detergent/dispersant/anti-deposit build-up/anti-sludge = TBD
TBN = TBD
The onset of thermal breakdown is approximately 265*
3. MOBIL 1 TURBO DIESEL TRUCK, 5W40 synthetic, API CJ-4, CI-4 Plus, CI-4, CH-4 and ACEA E7
“Load Carrying Capacity/Film Strength” = 74,312 psi
zinc = 1211 ppm
phos = 1168 ppm
moly = 2 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 1596 ppm
TBN = 9.3
The onset of thermal breakdown is approximately 270*
4. CHEVRON DELO 400LE, 15W40 conventional, API CJ-4, CI-4 Plus, CI-4, CH-4, SM, SL, “Load Carrying Capacity/Film Strength” = 73,520 psi
zinc = 1519 ppm
phos = 1139 ppm
moly = 80 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 2205 ppm
TBN = 8.0
The onset of thermal breakdown is approximately 265*
5. MOBIL DELVAC 1300 SUPER, 15W40 conventional, API CJ-4, CI-4 Plus, CI-4, CH-4/SM, SL , “Load Carrying Capacity/Film Strength” = 73,300 psi
zinc = 1297 ppm
phos = 944 ppm
moly = 46 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 1843 ppm
TBN = 9.8
The onset of thermal breakdown is approximately 250*
6. Farm Rated 15W40 Heavy Duty Performance Diesel, conventional, API CI-4, CH-4, CG-4, CF/SL, SJ
“Load Carrying Capacity/Film Strength” = 73,176 psi
zinc = 1325 ppm
phos = 1234 ppm
moly = 2 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 1593 ppm
TBN = 9.3
The onset of thermal breakdown is approximately 255*
7. SHELL ROTELLA T, 15W40 conventional, API CJ-4, CI-4 Plus, CH-4, CG-4, CF-4,CF/SM
“Load Carrying Capacity/Film Strength” = 72,022 psi
zinc = 1454 ppm
phos = 1062 ppm
moly = 0 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 2886 ppm
TBN = 9.1
The onset of thermal breakdown is approximately 250*
NOTE: This new Rotella T has SIGNIFICANTLY MORE zinc than the OLD
Rotella T, NOT LESS as is often claimed. And these two Rotella oils
were Lab tested more than a month apart. So, their component
quantities had no chance of being mixed up. This new Rotella’s wear
protection capability is just slightly BETTER than the OLD Rotella.
Therefore, the new Rotella is NOT the junk some have claimed.
8. “OLD” SHELL ROTELLA T, 15W40 conventional, API CI-4 PLUS, CI-4, CH-4,CG-4,CF-4,CF,SL, SJ, SH
“Load Carrying Capacity/Film Strength” = 71,214 psi
zinc = 1171 ppm
phos = 1186 ppm
moly = 0 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 2715 ppm
TBN = 10.1
The onset of thermal breakdown is approximately 250*
NOTE: There is ABSOLUTELY NOTHING special about this OLD Rotella, as
so many have always claimed. That was only folklore. It is simply
ordinary Diesel oil.
9. VALVOLINE PREMIUM BLUE HEAVY DUTY DIESEL, 15W40 conventional, API CJ-4, CI-4 Plus, CI-4, CH-4, CG-4, CF-4, CF/SM
“Load Carrying Capacity/Film Strength” = 70,869 psi
zinc = TBD
phos = TBD
moly = TBD
total detergent/dispersant/anti-deposit build-up/anti-sludge = TBD
TBN = TBD
The onset of thermal breakdown is approximately 255*
10. CHEVRON DELO 400LE, 5W40 synthetic, API CJ-4, CI-4 Plus, CI-4, SL, SM,
“Load Carrying Capacity/Film Strength” = 69,631 psi
zinc = TBD
phos = TBD
moly = TBD
total detergent/dispersant/anti-deposit build-up/anti-sludge = TBD
TBN = TBD
The onset of thermal breakdown is approximately 255*
11. SHELL ROTELLA T6, 5W40 synthetic, API CJ-4, CI-4 Plus, CI-4, CH-4, CG-4/SM
“Load Carrying Capacity/Film Strength” = 67,804 psi
zinc = TBD
phos = TBD
moly = TBD
total detergent/dispersant/anti-deposit build-up/anti-sludge = TBD
TBN = TBD
The onset of thermal breakdown is approximately 260*
12. LUCAS 15W40 MAGNUM Diesel Oil, conventional, API CI-4,CH-4, CG-4, CF-4, CF/SL
“Load Carrying Capacity/Film Strength” = 66,476 psi
zinc = 1441 ppm
phos = 1234 ppm
moly = 76 ppm
total detergent/dispersant/anti-deposit build-up/anti-sludge = 3393 ppm
TBN = 11.7
The onset of thermal breakdown is approximately 250*
13. CASTROL GTX DIESEL, 15W40 conventional, API CJ-4, CI-4 Plus, CI-4, CH-4, CG-4, CF-4/SN
“Load Carrying Capacity/Film Strength” = 66,323 psi
zinc = TBD
phos = TBD
moly = TBD
total detergent/dispersant/anti-deposit build-up/anti-sludge TBD
TBN = TBD
The onset of thermal breakdown is approximately 265*
The average value for Thermal Breakdown among the conventional Diesel
oils here, was 255*, which is 17* LOWER than among the conventional
gas engine oils I’ve tested.
The average value for Thermal Breakdown among the synthetic Diesel
oils here, was 267*, which is 15* LOWER than among the synthetic gas
engine oils I’ve tested.
And as you can see with these Diesel oils above, zinc levels alone do
NOT establish their wear prevention ranking. The zinc levels are
randomly up and down, relative to the ranking order. And as you will
see in the link to my motor oil ranking list below, zinc levels
clearly have NOTHING to do with an oil’s protection capability or
ranking order. Also, anyone who has followed my motor oil testing this
year, probably noticed that these Diesel oil “Load Carrying
Capacity/Film Strength” psi values are rather low, with an average
value for the whole group of only 72,408 psi. This number would put an
oil for gasoline engines, only in the MODEST PROTECTION category
(60,000 to 75,000 psi).
And considering that these oils are intended for use in heavy duty
working Diesel engines as used in big rigs, bulldozers, locomotives,
etc, etc, you probably expected to see some rather impressive psi
numbers. But, if you were expecting that, you were obviously
disappointed and maybe even shocked. So, what’s going on here?
Obviously since all these diesel oil numbers are so closely clustered
together with only about a 20,000 psi range (compared to the gas
engine oil numbers which have a much larger range of almost 60,000
psi), it is clear that the oil companies intentionally formulated them
to be in this general range. Why would they do that? How can that be
good enough for these hard working diesel engines?
Diesel engines of this type are made very rugged and very durable for
the long haul. And in order to accomplish that, the engine’s
components are designed and sized to keep the part loading at a modest
level. And of course, these engines are known primarily for their
impressive low end torque under boost, but NOT for their high rpm HP.
All that being the case, these oils don’t need to have a higher
capability. And this type of Diesel engine typically takes a LOT OF
OIL. So, cost becomes a real factor when changing oil. This means that
no oil company is going to make their products way better than needed,
because that would make their products too expensive to be competitive
in the marketplace.
And no one can complain that my test equipment and test procedure do
not allow high zinc oils to perform at their highest level. Because
here are some high zinc (over 1100 ppm) conventional, semi-synthetic,
and full synthetic gasoline engine oils that I’ve tested previously.
And they all had test results over 90,000 psi, which put them in the
“OUTSTANDING PROTECTION” category for gasoline engines.
10W30 Lucas Racing Only, full synthetic = 106,505 psi
zinc = 2642 ppm
phos = 3489 ppm
moly = 1764 ppm
10W30 Valvoline NSL (Not Street Legal) Conventional Racing Oil = 103,846 psi
zinc = 1669 ppm
phos = 1518 ppm
moly = 784 ppm
10W30 Valvoline VR1 Conventional Racing Oil (silver bottle) = 103,505 psi
zinc = 1472 ppm
phos = 1544 ppm
moly = 3 ppm
10W30 Valvoline VR1 Synthetic Racing Oil, API SL (black bottle) = 101,139 psi
zinc = 1180 ppm
phos = 1112 ppm
moly = 162 ppm
30 wt Red Line Race Oil, full synthetic = 96,470 psi
zinc = 2207 ppm
phos = 2052 ppm
moly = 1235 ppm
10W30 Amsoil Z-Rod Oil, full synthetic = 95,360 psi
zinc = 1431 ppm
phos = 1441 ppm
moly = 52 ppm
10W30 Quaker State Defy, API SL (semi-synthetic) = 90,226 psi
zinc = 1221 ppm
phos = 955 ppm
moly = 99 ppm
SUMMARY
Thermal Breakdown BEGINS SOONER with Diesel oil, than with gas
engine oils, which is not desirable for High Performance gas engine
usage. And as you can see by looking at this short list of “high zinc”
gas engine oils, or by looking at the complete ranking list below,
there are many, many gas engine oils available that are FAR SUPERIOR
to the best Diesel oils in terms of wear protection. Therefore, using
Diesel oils in high performance gas engines is NOT the best choice, if
you want superior wear protection with plenty of margin of safety
(extra reserve wear protection above what the engine typically needs).
For those who have used Diesel oil in High Performance gas engines for
years without issue, you were able to do that only because the wear
protection required by the engines, never happened to exceed the oil’s
capability. But, you were clearly running a MUCH LOWER margin of
safety than you would have been, if you’d used a much more capable gas
engine oil instead. So, if you’ve been using Diesel oil in High
Performance gas engines, you may want to rethink what you’ve been
doing and consider upgrading to one of the far better gas engine oils.
CONCLUSION
The bottom line is that the end user does NOT know more about motor
oil than the Oil Companies’ Chemical Engineers and Chemists. So, the
BEST choice is to use only quality gas engine oil in High Performance
gas engines. These oils offer MUCH HIGHER wear protection capability
and can withstand somewhat higher temperatures before the onset of
Thermal Breakdown. Leave the less capable Diesel oils for use only in
Diesel engines, where they are meant to be used.
Of course all those tests do not test diesel oils with the proper speced viscosity for a Harley unless you are riding in temps below 40 degrees Fahrenheit.
Originally Posted By: BigCahuna
To bring some of you up to speed about Harley oil here's some interesting info. While Harley's oil that's sold thru their dealership network is highly recommended by Harley for use in their motorcycles,does not carry an API symbol. They just say it's the oil to use and charge premium $$$ for it. That also goes for about every other motorcycle specific oil sold. Amsoil, Mobil 1 V-Twin oil, Valvoline ect. They say it meets a SG spec and is GL-1 rated, but only they test it. So why does Harley recommend an diesel oil that carries a higher spec then their own oil, when there are oils available that have proven to be of better quality or at the very least, as good as their own?. Soot and combustion gases have never been a issue with Harley's like they are with diesel motors, so why would this oil be preferred over any 20/50 wt with a SG rating?.,,
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Originally Posted By: SJohnson
I believe it's all about marketing. Why would Harley recommend a 20/50 oil from a different manufacturer? That would cut into their market share. Try and find a readily available 20/50 that meets the latest HDEO spec. They are few and far between. Since most people want to run a 20/50 in their Harley and Harley recommends their 20/50 first and then a HDEO 15/40 second, I believe most people will opt for Harley oil. Unlike PCMO and HDEO, there is no spec for "MC specific" oil. So Harley recommends their 20/50. It's all about marketing and the bottom line. I'm sure if it wasn't working out for them, they would change. I guess they figure if it ain't broke, don't fix it.
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It still doesn't explain why Harley as a manufacturer doesn't list a spec from an API rated oil like they used to. They changed from recommending a SG rated oil, to diesel oil with ratings for things that a Harley motor doesn't need or require. If you can look past the diesel ratings and look directly at what it is in an oil you want for proper protection,there are lots of oils that exceed Harley's own oil.So why wouldn't you choose those?. Most aftermarket motorcycle specific oils anti wear ingredients are higher then Harley's. And availability of 20/50 wt oil for those are pretty much everywhere. I personally haven't seen 20/50 wt diesel oil in any of the auto part stores where I live, so using that isn't a option in a pinch. So it seems Harley is trying to be cute buy recommending a diesel oil for their bikes, because the Magnesson moss act said they have to give you oil for free if their's is the only oil that can be used in their bikes.Knowing full well that just about any oil on the planet will, and has been used without problems.,,
"CONCLUSION
The bottom line is that the end user does NOT know more about motor
oil than the Oil Companies’ Chemical Engineers and Chemists. So, the
BEST choice is to use only quality gas engine oil in High Performance
gas engines. These oils offer MUCH HIGHER wear protection capability
and can withstand somewhat higher temperatures before the onset of
Thermal Breakdown. Leave the less capable Diesel oils for use only in
Diesel engines, where they are meant to be used."
I disagree with the statement above. I think the best oil recommendation comes from the maker of the engine. There are a HUGE amount of variations on engines, more so on motorcycle engines, I doubt VERY MUCH that Joe Public can read so called "test results" on motor oil and determine they are smarter then the maker of the engine maker and choose a better oil based on UOAs, VOAs and PSI pressure tests, all for the wrong reasons and many of these "self made" tests are not verified by anyone.
Many people even reading these forums will not even know, these pressure tests do help one determine how much torture an oil can stand but what difference does it make being the pressures testes are a FRACTION of what occurs in a Vtwin motorcycle engine? or diesel engine for that matter.
Its easy to look at one test and think one oil is better to Joe Public over the other but what if the test has nothing to do with the reason for the choice of oil to begin with, what if makers are more concerned with wear, bearings and real world sludge or engine deposits, such as in diesel engines and motorcycle engines where oil is sprayed on the bottom on the pistons to help cool them or any other host of concerns, they may not care if the pressure the oil can take is 10 times more then required.
Just thoughts I am throwing out there, I can get caught up in this stuff too but real world tests vs internet postings ... well, only documented real world standardized tests are done by Amsoil that I have seen.
With that said, I do like reading this guys tests and I love the information but my mind says, there is a reason for everything. Example, looking back a decade or two when we found out some synthetics were causing premature wear in some flat tappet and other engines, heck, even Kawaski had a problem with that, yet I am sure the synthetics would have still done well in the pressure wear tests, yet real world wear was WAY worse for some people over regular cheap conventional oil. Anyway, just thoughts today, and I do love reading this stuff but over the years I am thinking more for the wrong reasons.
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"It still doesn't explain why Harley as a manufacturer doesn't list a spec from an API rated oil like they used to. They changed from recommending a SG rated oil, to diesel oil with ratings for things that a Harley motor doesn't need or require. If you can look past the diesel ratings and look directly at what it is in an oil you want for proper protection,there are lots of oils that exceed Harley's own oil.So why wouldn't you choose those?...."
Im not disagreeing with you, just explaining why I choose the oil I do, we all have our "thing" as to why in here. In your case you think a Harley Motor doesnt need or require a diesel rating but maybe they do for the past reason stated in your original post.
You state Harley went from a SG oil to a C oil, there might or might not be a reason after years of experience with SG oil why they did, as they might think the diesel oil solves an issue they became aware of, such as engine deposits and the higher temperatures of the lean fuel mixtures. I have no idea but no one ever will but diesel oils, taken from your post are for "CH-4 oils provide superior control over high temperature piston deposits, wear, corrosion, foaming, oxidation stability " maybe that is more of an issue for Harley. I dont know, maybe its purely marketing but maybe its not. But lets not signal out Harley alone, many bike makers and automakers will at times specify a specific type of oil, high end cars as well.
Again, for me, still fresh under warranty and in my mind, no reason to switch, Conventional HD 360 is a fine oil, granted about $2 or so more a quart, not to outrageous, turns in good UOAs, if I want to go higher, Amsoil 20/50 full synthetic diesel at $11 a quart or Mystik 15/50 semi synthetic at less then $5 a quart. If no Oreillys autoparts near you, it can be found online about the same price delivered, it does take some hunting though.
Whatever oil one chooses in this forum their engine will last a long time, simply because they are aware regular maintenance and oil changes are the most important.
Wouldnt it bet great in motorcycle forums if every time someone has a mechanical problem, be it a spun bearing, bad bearing, blown transmission, etc, etc, they listed what oil they regularly use and how often they change?
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If there weren't better choices of oil for any vehicle then diesel oils, why do they make them? Car manufacturers have specs for their motors, and I've never heard one state you "must" use our oil, or an oil designed for offshore racing motors. Harley motors are so basic and plain compared to other motorcycle motors out there, it doesn't seem they need anything "special" in the way of oil to keep them clean. Isn't that what the job of the oil filter is for anyway?. I'e never heard anyone prove varnish inside a motor caused any harm. When looking at a VOA you wouldn't chose an oil with the lowest anti-wear additives would you? or an oil with the lowest flash point or TBN?. Like I said you can run just about any oil out there and it will work just fine. Alot of Harleys motor problems can be traced back to poor engineering on Harley's part, not the oil that's been used in them.,,
I offer the following thoughts.
HD 360 is a rating, as far as I know SYN3 and Genuine HD are the only oils so rated.
The owners manual only states that Diesel oils (It then gives 3 ratings and 3 viscosities) can be used if the "Preferred" oil is not available and that the oil should be changed back to 100% HD oil "At the first opportunity".
A Harley Davidson has a fairly large bore, much larger than the average new car - I suspect.
A Harley Davidson uses bearings that are not similar to most modern car engines.
A Harley Davidson has a dry sump type lubrication system
I believe all new Harley Davidson motorcycles include a catalytic converter.
It is possible that HD feel that CH-4, CI-4 or CJ-4 oil is likely to contain a more compatible additive package to HD oil, and it appears those 3 diesel ratings are for emission controlled applications.
Magnusson-Moss deals with Warranties and the oft quoted provision relates to tie in sales and warranty language. Once you get outside of the written warranty it is difficult to apply MM.
It would be interesting to hear technically if there is any thing about the engines design or the qualities of the specified oils that make them particularly compatible.
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