Shear Stability and the OEM's Philosophy

[mhdelano]

It's been proven time and time again that the 5w-40 and 10w-40 oils quickly shear out of grade in a shared sump motorcycle engine. My question is, why would 10w-40 be the most common recommended oil weight by the manufacturer's? They must know that the 10w-40 grade shears, and yet they still recommend it. The only explanation I can think of is that a sheared down 10w-40 oil must still be providing adequate lubrication. I find it hard to believe that the manufacturers would recommend a 10w-40 oil if it were a problem. Thoughts?

I mean, we routinely see 10w-40 oils shear down to a 30 weight by 1500 miles, yet most of the OEM's recommend around 4000 mile OCI's. This must be an acceptable result, otherwise it wouldn't be a recommended type of oil, right?

 

[Quattro Pete]

Originally Posted By: mhdelano
This must be an acceptable result, otherwise it wouldn't be a recommended type of oil, right?

Correct. Some oil shear is normal and factored in mfg oil recommendations.

Welcome to BITOG! It only took you 3 years to make a first post.

 

[mhdelano]

I guess one way to look at it is, if the oem standards are so low, just use the cheapest oil that meets the requirements of non energy conserving API SG or higher. Waddayaknow, HDEO's!! Not only are they cheap but have been proven to show little wear.

Is that the thinking around here?

 

[Quattro Pete]

Yup, you'll see a lot of people here running HDEOs in their bikes, myself included.

 

[rrounds]

My '98 Honda VT1100-T says to change the oil every 8k miles, I go 4 to 4.5k miles and it comes out like water when its warm to hot. I just can't let it go 8k miles, it starts to use a little oil when I have around 2.5k miles on the oil. All I use is 5w40 T6 or Delo400 15w40.

ROD

 

[mhdelano]

Wow, even the HDEO's come out like water at 4k OCI? I just bought a Honda 599 that's gonna need an oil change soon.

I wish a honda motorcycle powertrain engineer would answer a bunch of these questions.

 

[Sonic]

Yeah, I've wondered about starting out with a 40 grade oil myself. My shared sump v star says you can use either 10w40 or 20w50 for like 3000-4000 miles, only makes sense to start with the 50 grade because of shearing. I have used T6 5w40 (in cold weather)but I didn't run it too long before going back to a 20w50 15w50 mix of M1. I think from now on I'll stick with xxw50 oil so I'm not wondering about protection after just 1000-1500 miles. Although I guess a 15w40 HDEO is supposed to hold up well against shearing so maybe in the cooler months I'll give that a go and see how it runs.

 

[Robenstein]

Well I know we worry about oil on this site, but I still see high mileage old KZ750, KZ900 and CB750 bikes running around locally that have probably only had 10w40 their whole life. They are still around 30 years later. Sure it shears, but if the design is solid it seems to do the job.

But it is something I have also seen even in my Virago 250. Thats why I like to run HDEO, I have seen Royal Purple 10w40 go out of grade in a 2k OCI.

 

[beanoil]

Yamaha used to recommend their 20w40 back in the day. It was likely to be slightly more shear stable than a 10w40. Honda has recommended since around 08 or so the use of 10w30's in many bikes, including the ST1300 and the Gold Wing. Seems to work just fine according to the ST chat board I frequent, and shears less than a 40 weight. But both of those bikes have a reputation of being really easy on oil in spite of their shared sumps and wet clutches.

 

[sunruh]

um, yamaha still recommends 20w40 on a brand new 2013 bike like mine. why? because its only available in yamalube bottles and guess who happens to stock that? yep, just the dealerships.

robenstein, i have a used oil analysis where RP dropped out of grade in 80 miles.

oil today is better than it ever has been. but the bikes also produce way more hp than ever before as well.

steve

 

[kmrcstintn]

my local Yamaha dealers stock 10w-40 and 20w-50 Yamahalube and the owners' manual for my 2009 V Star 650 recommends 10w-40 or 20w-50 (the sticker on the frame states 10w30 or 20w-40)...a bit confusing, but not alot of sources for 20w-40 in the US, hence the updated change in the owners' manual for 10w-40 or 20w-50

 

[rraiderr]

Originally Posted By: sunruh
um, yamaha still recommends 20w40 on a brand new 2013 bike like mine. why? because its only available in yamalube bottles and guess who happens to stock that? yep, just the dealerships.

robenstein, i have a used oil analysis where RP dropped out of grade in 80 miles.

oil today is better than it ever has been. but the bikes also produce way more hp than ever before as well.

steve


The man has spoken.

 

[vo_marz]

anything with a 40 at the back , i'd start with at least 4.3 HTHS
anything with a 50 at the back, 3.9

my motor chews up oil like nuts, YMMV

 

[HerrStig]

SAAB listed 10-30 for their manual transmission fill, and, as I recall, 25 K as a change interval. I put 400K on one SAAB manual doing that.