Blackstone Labs Oil Analysis

[carbonation]

A UOA isn't the end all solution. It will show you a trend if you are consistent with doing them. You go along 4,5 analysis, and see iron trend with miles. then you get a result on analysis 6 showing iron has jumped 3 fold. That might indicate a problem.
A UOA is useless if you switch brands every time. It can be useless at times with brand consistency because of reformulation of the product.
I used Mobil 15w50 for a long time in other machines. UOA were great. Mobil switched from a healthy dose of PAO to their Visom base, and results went to heck in comparison to to previous results.
You folks running Amsoil and Mobil are in pretty good company. Both companies would have an enormous amount of reputation to lose if something went boink with their product.
I've chosen Motul for mine, and will be trying both 7100 and 300V over the next several changes. I like their ester base technology, and it's on par at 11.xx a liter (7100, 300V is a bit more) with Amsoil.

 

[BajaRon]

A UOA isn't the end all solution. It will show you a trend if you are consistent with doing them. You go along 4,5 analysis, and see iron trend with miles. then you get a result on analysis 6 showing iron has jumped 3 fold. That might indicate a problem.
A UOA is useless if you switch brands every time. It can be useless at times with brand consistency because of reformulation of the product.
I used Mobil 15w50 for a long time in other machines. UOA were great. Mobil switched from a healthy dose of PAO to their Visom base, and results went to heck in comparison to to previous results.
You folks running Amsoil and Mobil are in pretty good company. Both companies would have an enormous amount of reputation to lose if something went boink with their product.
I've chosen Motul for mine, and will be trying both 7100 and 300V over the next several changes. I like their ester base technology, and it's on par at 11.xx a liter (7100, 300V is a bit more) with Amsoil.

Not to be contrary, but I disagree somewhat here. If you get 1 test and it shows that your oil has sheered down from the rated 40 weight to 20 weight. I'd say that information alone is worth the $28.00 for the test. By the same token. If it shows that you went from 40 weight to 36, that is also valuable information. All oils suffer over the miles. It's how much they degrade that this analysis can tell you on the first test. Not only that. But Blackstone, and most other services, will tell you what their extensive database shows as a good report average in each category to compare your results to. This also gives you a valuable status report on how things are going inside on the very first test. If you have an outlier, that will show up. Blackstone also gives recommendations based upon the test results. As in, 'You need to change your oil sooner. Or, 'You can go miles on this oil'. Or, 'You're service interval is just about right for this application'.

Granted. To get the most out of this tool it needs to be used with each oil service, because trends and comparison are the strong points here. But even just 1 analysis can be very useful. As always, just my opinion.

 

[jcoats1]

WOW, when do you guys have time to ride?

 

[Highwayman2013]

I believe in checking the virgin oil analysis vs the used oil analysis in comparable equipment. In some instances different manufacturers start out with a heavier base, which will show up as less sheared down on an equal mileage test. These lab reports (UOA) are great to tell you about viscosity breakdown if you know the starting point (VOA), and give you the remaining TBN. I know it's not rat540, but if you like making your own decisions there is a wealth of information here; https://www.bobistheoilguy.com/forums/ubbthreads.php/category/5/oil-analysis-reports . I'm with PMK, in the industry I was in we tore big engines down based on some of the reports and found nothing wrong, and also saw instances where green flagged engines has a bearing failure that went unnoticed. It is my belief that for most of us, the oils used today are so far ahead of oils even 30 years ago as far a protection goes that worrying about which oil is pointless. Pick a good brand that you trust, that has the specification for the equipment you're running it in, at a cost you want to pay. IT will be more than adequate for the mileage interval set forth. Most of us will never make the 9300 mile change every year, and fall between 2000-7500 miles.

To put this in perspective about overthinking oil, I bought a used tractor because I wanted one I could work on without all the computer and smog equipment. It had only around 250 hours on it. I picked a top quality synthetic oil that met the specs of the motor. Doing the math, I figure that at 100 hours per year use, and knowing these tractors go into the 5000-8000 hour range before any normal wear problems manifest, I figure I'll be about 105 years old before I need to do something mechanically to it. Use good oil, change it periodically, and inspect the filter element and magnets at each change. Your Spyder will probably outlast you.

Who is rat540 and what makes them so special? Why do you have to change oil every year?

 

[PMK]

Who is rat540 and what makes them so special? Why do you have to change oil every year?

The manual from BRP has the recommended oil change listed by mileage and calendar months. The calendar months is more important in areas of wide temperature changes. Personally I typically go a month or two past 12 months and hit the mileage number I use of 5000 miles. Temps here are fairly stable and while humid, the machine is stored indoors and run enough not to be a concern.

540rat, is a, in my opinion, very smart and talented person. He has been independently testing and rating oils for years. He offers very accurate repeatable results, and his test methods are real world based on friction and heat. In his blog he gives insight into what he tests for and why. His blog is a long read, but if you understand and read it all, it is very informative.

Since he is not accepting money from oil companies to test their oils, he purchases each oil tested. I have never noticed him holding back and calls it as it rates. Previously, I would sometimes visit Bob is the oil guy website. I found, unfortunately that the posts there were often heavily opinionated without true facts. 540Rats blog is like Joe Friday, just the facts with test data to back it up.

As I mentioned before, I have not yet seen 540Rat test Amsoil motorcycle oil. He has tested a various Amsoil automotive and truck oils. Some Amsoil products did very well, others not so well. Myself, using 540Rats ranking list of oils, I use Mobil 1 10w40 Racing Motorcycle oil and it is the number 2 wet clutch rated motorcycle oil behind Motul 300v. Other popular oils such as Rotella T6 and Valvoline are on the rankings also. It takes a bit of reading and small effort to compile and segregate the motorcycle and popular oils out from the automotive oils. Not bad, just a bit of extra effort.

 

[RICZ]

PMK....Has 540rat tested Rotella T-6? If he has, can you give us a Readers Digest version of what he said about it? Pretty please!

 

[PMK]

PMK....Has 540rat tested Rotella T-6? If he has, can you give us a Readers Digest version of what he said about it? Pretty please!

He has, it rated well below Mobil 1 10w40 Racing Motorcycle oil. But the flip side is the Rotella T6 is a lot less money than Mobil 1.

Truthfully, you should take the time and read the details for yourself. I learned about 540Rat from another Spyder person here on Spyderlovers during a discussion about zinc additives. I was always schooled that zinc was good. The 540Rt has all sorts of test data about zinc and honestly I learned I was wrong. Sadly, my previous knowledge was based on oil manufacturers and engine manufacturers info. 540Rats testing taught me otherwise.

 

[h0gr1der]

Not to be contrary, but I disagree somewhat here. If you get 1 test and it shows that your oil has sheered down from the rated 40 weight to 20 weight. I'd say that information alone is worth the $28.00 for the test. By the same token. If it shows that you went from 40 weight to 36, that is also valuable information. All oils suffer over the miles. It's how much they degrade that this analysis can tell you on the first test. Not only that. But Blackstone, and most other services, will tell you what their extensive database shows as a good report average in each category to compare your results to. This also gives you a valuable status report on how things are going inside on the very first test. If you have an outlier, that will show up. Blackstone also gives recommendations based upon the test results. As in, 'You need to change your oil sooner. Or, 'You can go miles on this oil'. Or, 'You're service interval is just about right for this application'.

Granted. To get the most out of this tool it needs to be used with each oil service, because trends and comparison are the strong points here. But even just 1 analysis can be very useful. As always, just my opinion.

I've never used Blackstone, but I often wondered if the guys doing our industrial testing for all our engines were ever competent. We'd send in a diesel engine oil sample, black and thin from fuel contamination, having reached borderline on the last sample, only to have it come back as good to go for another xxx time period. Go figure! Makes me wonder.

 

[Highwayman2013]

I think it is pretty simple to figure if two oils are rated 40 weights and one doesn't stay a 40 then it doesn't hold up as well.

 

[PMK]

I think it is pretty simple to figure if two oils are rated 40 weights and one doesn't stay a 40 then it doesn't hold up as well.

Related, and more critical than engine oil is suspension fluid. As a suspension tuner, we purchase suspension fluid by viscosity listed as weight. As an example 5wt.

Sadly, because the range of what determines SAE 5wt is wide and varied, I must resort to other more accurate measurements of viscosity. This is why the common reference of Cst at 40* and 100* is used. Much more accurate and consistent.

With suspension fluid, I typically use a well respected chart of various brands and wts to compare when rebuilding rear shocks or forks. Very common to see some 5 wts as thin as some 2 1/2 wts, and some 5 wts in the 7 1/2 wt range. Altering race bike suspension by this amount is not good, as the internal valving was setup specifically for the riders ability and their riding weight, plus the track.

So, leaning back to your reference to SAE 40wt oil. When new, it is quite possible one brand is on the upper viscosity end of SAE 40 when new, while the second brand may be rated 40wt but begins at a truer lower viscosity when compared by Cst rating.

So important to know what new viscosity is compared to your oil analysis sample.

 

[BajaRon]

I've never used Blackstone, but I often wondered if the guys doing our industrial testing for all our engines were ever competent. We'd send in a diesel engine oil sample, black and thin from fuel contamination, having reached borderline on the last sample, only to have it come back as good to go for another xxx time period. Go figure! Makes me wonder.

I can't speak to what appears to be a testing inconsistency here. Could have been a miss labeled sample if you are doing quite a few. Or, miss handled at the lab. But I can tell you that all diesel oil is going to be black pretty quick after an oil change. Here is what one diesel website states. 'It is normal for diesel motor oil to turn black quickly. The dark color is a sign that the oil is performing correctly by keeping byproducts of the combustion process in suspension. Higher fuel injection pressures in newer diesel engines produce lower exhaust emissions, but produce more soot. This quickly turns diesel motor oil black. In fact, it would be abnormal for the oil to stay clear.'

Related, and more critical than engine oil is suspension fluid. As a suspension tuner, we purchase suspension fluid by viscosity listed as weight. As an example 5wt.

Sadly, because the range of what determines SAE 5wt is wide and varied, I must resort to other more accurate measurements of viscosity. This is why the common reference of Cst at 40* and 100* is used. Much more accurate and consistent.

With suspension fluid, I typically use a well respected chart of various brands and wts to compare when rebuilding rear shocks or forks. Very common to see some 5 wts as thin as some 2 1/2 wts, and some 5 wts in the 7 1/2 wt range. Altering race bike suspension by this amount is not good, as the internal valving was setup specifically for the riders ability and their riding weight, plus the track.

So, leaning back to your reference to SAE 40wt oil. When new, it is quite possible one brand is on the upper viscosity end of SAE 40 when new, while the second brand may be rated 40wt but begins at a truer lower viscosity when compared by Cst rating.

So important to know what new viscosity is compared to your oil analysis sample.

You are 100% right about this. I used to do a lot of dirt bike riding and changing out fork fluid (and sometimes rebuilding rear shocks) can be a real eye opener as viscosities are all over the map. You can't trust them. You can get 3 different brands of the same viscosity and they will perform much different, which they should not. And you are right again about motor oils. There is a spread for each weight. If the oil falls within a certain range, it's called 40 weight. Even if it's actually only a 36 weight to begin with. Knowing this will help you determine how much it has degraded from the starting point. But this is not as important as the final test sample number as 20 weight is 20 weight, regardless of where it started out.

 

[troop]

Other than my owned since new 2009 H-D FLHT, my last two bikes prior to my Spyder were a Yamaha FZ09 and Triumph 800 Tiger XCx. Since those bikes both used 10w40, I started collecting oil on sale/clearance. I accumulated quite a stash over time, with at one point, having about 20 quarts on hand. All good stuff, with the current stash being Castrol 10w40 Actevo partial syn, Castrol Power 1 10w50, M1 4T10w40 and Quicksilver 10w40 full syn m/c. I paid as low as $2.50/qt for the Quicksilver, and as high as $5/quart for the Castrol Power 1 10w/50. I was glad to read on BITOG/here that 10w40 is, generally, the go to oil as I still had quite a stash of it. My current/end of season change is: (1.5)qts Castrol 10w40 Actevo syn blend, (2)qts M1 10w40 4t and (2)qts Quicksilver 10w40 m/c syn. Thinking come the end of the season, I'll send it in and see how it looks. Might have 5k miles or it might have 8k, but I'll be interested. On a side note, what is up with Can-Am and BRP with oil change capacities ?? 2018, 2019 and 2020 SE6 models all have different capacities !!
2018:
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
4.7 L
(5 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
4.9 L
(5.2 qt (U.S. liq.


2019:
OIL CAPACITY
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
5.2 L
(5.5 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
5.4 L
(5.7 qt (U.S. liq.))


2020 SE6:
IL CAPACITY
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
4.7 L
(5.0 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
4.9 L
(5.2 qt (U.S. liq.))

And, PMK, I hear you on suspension viscosity. Dealt with that on my suspension upgrades on my FZ09 and 800 Tiger. Oil weights are not created equal
http://mahonkin.com/~milktree/motorcycle/fork-oil.html

 

[PMK]

View attachment 178169I have and it came out great. Much better than Mobil 1. Amsoil on the left Mobil 1 on the right. 1,000 more miles on the Amsoil.

Highwayman, always appreciate you sharing info and asking questions.

Looking at your oil sample sheet, Blackstone lists the oils initial viscosity range in the 11.6 / 14.8 range. I went to the Mobil and Amsoil website, gathering the manufacturers data for Cst @ 100*c.

Amsoil claims the 10w40 synthetic motorcycle oil when new is 14.6 Cst @ 100*c
Mobil claims the 10w40 motorcycle oil when new is 13.4 Cst @ 100*c

With that basis, the Amsoil begins life more viscous, even though 40wt, when compared to Mobil 1.

Using Blackstones range of 11.6 to 14.8, it is apparent that the Amsoil starts very near the upper limit of Blackstones 40wt criteria, while Mobil 1 falls into a point just above the median point.

When comparing the used oil values, we expect the thicker oil to typically survive better. Granted the Amsoil has more miles on it and makes a perfect comparison impossible.

Your results indicate the Amsoil sheared from 14.6 to 13.06, so a drop of 1.54 Cst @ 100* c
Your results indicate the Mobil 1 sheared from 13.4 to 11.45, so a drop of 1.95 Cst @ 100*c

Because the Mobil 1 sheared below Blackstones range of 11.6, the rating of 11.45 Cst put it just under their 40 wt range and had the results shown as bold.

Knowing the Mobil started with a lower viscosity, and knowing lower viscosity tends to shear more easily, but it did have fewer miles, the results seem good.

Same with Amsoil, it started life more viscous, should hold up better on account of being more viscous, had a bit more miles, it showed slightly, and I mean very slightly better results.

That said, both oils seem good. I will say the Mobil is more truly a 40 wt, while the Amsoil leans well towards a lower range 50 wt.

My point in all this, as I learned long ago as a suspension tuner, SAE viscosity is a very wide range, while Kinematic viscosity is quite precise. There is more science in all of it without doubt.

I do wait for the test from 540rat that maybe someday he tests the Amsoil 10w40. I believe the Amsoil will do well on the wear test and we may find that these two oils, priced similar, are both excellent oils that are JASO MA and MA2 rated.

Hoped that helped explain how 40wt can differ a lot.

 

[PMK]

Other than my owned since new 2009 H-D FLHT, my last two bikes prior to my Spyder were a Yamaha FZ09 and Triumph 800 Tiger XCx. Since those bikes both used 10w40, I started collecting oil on sale/clearance. I accumulated quite a stash over time, with at one point, having about 20 quarts on hand. All good stuff, with the current stash being Castrol 10w40 Actevo partial syn, Castrol Power 1 10w50, M1 4T10w40 and Quicksilver 10w40 full syn m/c. I paid as low as $2.50/qt for the Quicksilver, and as high as $5/quart for the Castrol Power 1 10w/50. I was glad to read on BITOG/here that 10w40 is, generally, the go to oil as I still had quite a stash of it. My current/end of season change is: (1.5)qts Castrol 10w40 Actevo syn blend, (2)qts M1 10w40 4t and (2)qts Quicksilver 10w40 m/c syn. Thinking come the end of the season, I'll send it in and see how it looks. Might have 5k miles or it might have 8k, but I'll be interested. On a side note, what is up with Can-Am and BRP with oil change capacities ?? 2018, 2019 and 2020 SE6 models all have different capacities !!
2018:
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
4.7 L
(5 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
4.9 L
(5.2 qt (U.S. liq.


2019:
OIL CAPACITY
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
5.2 L
(5.5 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
5.4 L
(5.7 qt (U.S. liq.))


2020 SE6:
IL CAPACITY
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
4.7 L
(5.0 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
4.9 L
(5.2 qt (U.S. liq.))

And, PMK, I hear you on suspension viscosity. Dealt with that on my suspension upgrades on my FZ09 and 800 Tiger. Oil weights are not created equal
http://mahonkin.com/~milktree/motorcycle/fork-oil.html

Glad to see your linked document giving credit to Peter for his efforts compiling that viscosity chart.

As for Spyder oil quantities, do not even bother asking. Can Am has been essentially clueless about this for many years. Sort your best method whether it be start low and add when hot, or simply know how much from previous oil changes.

Your post was a bit confusing, sounds like you have plans to mix oils, your call but not something I like seeing done.

 

[PinkRosePetal]

....On a side note, what is up with Can-Am and BRP with oil change capacities ?? 2018, 2019 and 2020 SE6 models all have different capacities !!
2018:
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
4.7 L
(5 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
4.9 L
(5.2 qt (U.S. liq.


2019:
OIL CAPACITY
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
5.2 L
(5.5 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
5.4 L
(5.7 qt (U.S. liq.))


2020 SE6:
IL CAPACITY
MODEL WHEN
DOING... QUANTITY
Engine oil
and engine
oil filter
replacement
4.7 L
(5.0 qt (U.S. liq.))
SE6 Engine oil,
engine
oil filter
and HCM
surface
filter
replacement
4.9 L
(5.2 qt (U.S. liq.))

Yep, BRP is hopeless. We've got two 2017 bikes and they stipulate different capacities. I go for 5lts for a change including the filter. That's four oil changes from a 20lt drum... easy peasy.

On the viscosity thing, viscosity is not the most important feature of an engine oil, as witnessed by the actual viscosity range in centistokes relative to the labelled viscosity, and it's entirely possible to have an oil which loses a fair bit of viscosity but remains a better lubricant.

 

[troop]

I just went with what my manual said for oil capacity with filter, 5.5 qts on my 2019 SE6. Looked good on the stick when hot afterwords. Over 40 years of bikes, I mix/matched brands on many occasions. Some with different viscosities, some just different brands. Some agree, some don't agree. It's not a problem with the American Petroleum Institute, but, enough on that

 

[Highwayman2013]

Yep, BRP is hopeless. We've got two 2017 bikes and they stipulate different capacities. I go for 5lts for a change including the filter. That's four oil changes from a 20lt drum... easy peasy.

On the viscosity thing, viscosity is not the most important feature of an engine oil, as witnessed by the actual viscosity range in centistokes relative to the labelled viscosity, and it's entirely possible to have an oil which loses a fair bit of viscosity but remains a better lubricant.

How would we test for that?

 

[Highwayman2013]

Highwayman, always appreciate you sharing info and asking questions.

Looking at your oil sample sheet, Blackstone lists the oils initial viscosity range in the 11.6 / 14.8 range. I went to the Mobil and Amsoil website, gathering the manufacturers data for Cst @ 100*c.

Amsoil claims the 10w40 synthetic motorcycle oil when new is 14.6 Cst @ 100*c
Mobil claims the 10w40 motorcycle oil when new is 13.4 Cst @ 100*c

With that basis, the Amsoil begins life more viscous, even though 40wt, when compared to Mobil 1.

Using Blackstones range of 11.6 to 14.8, it is apparent that the Amsoil starts very near the upper limit of Blackstones 40wt criteria, while Mobil 1 falls into a point just above the median point.

When comparing the used oil values, we expect the thicker oil to typically survive better. Granted the Amsoil has more miles on it and makes a perfect comparison impossible.

Your results indicate the Amsoil sheared from 14.6 to 13.06, so a drop of 1.54 Cst @ 100* c
Your results indicate the Mobil 1 sheared from 13.4 to 11.45, so a drop of 1.95 Cst @ 100*c

Because the Mobil 1 sheared below Blackstones range of 11.6, the rating of 11.45 Cst put it just under their 40 wt range and had the results shown as bold.

Knowing the Mobil started with a lower viscosity, and knowing lower viscosity tends to shear more easily, but it did have fewer miles, the results seem good.

Same with Amsoil, it started life more viscous, should hold up better on account of being more viscous, had a bit more miles, it showed slightly, and I mean very slightly better results.

That said, both oils seem good. I will say the Mobil is more truly a 40 wt, while the Amsoil leans well towards a lower range 50 wt.

My point in all this, as I learned long ago as a suspension tuner, SAE viscosity is a very wide range, while Kinematic viscosity is quite precise. There is more science in all of it without doubt.

I do wait for the test from 540rat that maybe someday he tests the Amsoil 10w40. I believe the Amsoil will do well on the wear test and we may find that these two oils, priced similar, are both excellent oils that are JASO MA and MA2 rated.

Hoped that helped explain how 40wt can differ a lot.

So going by your math the Amsoil held up better. I would run either one to 10,000 miles in the spyder.

 

[PMK]

So going by your math the Amsoil held up better. I’m not saying Mobil 1 is bad it it doesn’t seem to be the best.

Based solely on viscosity change, possibly Amsoil held up better, but as I explained, the Amsoil starts life more viscous, and with that should shear less. So seeing a difference of 0.41 Cst is is in my opinion not even a percentage difference I would be concerned about. I do understand the Amsoil had more hours on it.

Simply to many variables, and the differences are so minute there is no way to offer up a good answer.

As I mentioned, I await the day that 540Rat rates the Amsoil. Then and only then, will we know how the oils compare in prevention of wear.

Regarding viscosity change vs use, they are both very good and differ very little.

The obvious answer though, time will tell.

 

[carbonation]

You are splitting hairs. Either AmSoil or Mobil 1 are fine. Depends on how long it's in, and riding conditions to say which is finer at any given moment.
BRP apparently expects shear and even blesses it when their oil cannot, will not, stay in grade over their prescribed change interval. Surely, many miles were done in testing, right? BajaRon has a point about an oil analysis and viscosity, I concede to that point of logic.
In my 998, nothing stayed in grade over only 4000 miles. Not AmSoil, not M1, not Liqui-Moly, Amalie, Valvoline MC, Mag-1, Castrol, nothing. All were a 30 weight, a couple were approaching a 20. Only one oil survived that thing. Valvoline straight weight 40 VR-1. Yes, they say, not good for wet clutch. Hogwash. I never had cold starts below 40 degrees, so no need for a multigrade. No VI to shear, stout Zinc and Phosphorus. It just worked. Went in a 40, came out the same way. Never that "BANG" I heard from other Spyders going into reverse, or into first. Just a soft "clunk".
I haven't done anything on this new 1330 yet, but have a change of Motul 7100 coming up, and a change of 300V planned. The 1330 seems to be a bit easier on the lubricant, both in the few oil analysis I've seen, and BRP over 9000 mile expectation.
Interesting read on viscosity.. https://www.machinerylubrication.com/Read/294/absolute-kinematic-viscosity
And another..https://www.api.org/~/media/Files/Certification/Engine-Oil-Diesel/Publications/4-Trends-in-Shear-Stability-of-Automotive-Engine-Oils.pdf
Simple answer, Conventional oils need more VI that can shear to achieve their rated weights, synthetics have a wider range naturally, and may need less VI, so they stay in grade better. Initially, the oil will shear, then stabilize for a while, then thicken over time with contaminant build up. Price point does matter, it would appear that more expensive oils have better components, including more shear stable VI, built in that you will pay for, up to a point.
You got to watch for bargains. AutoZone closed out Castrol Power1 for 2.00 a quart last fall. Massdrop just had Motul 7100 for 44. for 4 liters with free shipping, putting it in the AmSoil range. If you are crazy like me, Valvoline VR-1 goes on sale every spring at NAPA for 4 a quart. Driven HR-6 is a full synthetic mostly GRP III with a dose of PAO. Marketed toward HotRods, but perfect for wet clutch and is always less than 10 mail order.
It's been said. Pick an oil, ride, change, ride some more.