Rotella T5 syn-blend 15w-40

[Atesz792]

Originally Posted By: BusyLittleShop

Not a problem... Quote Kew Engineering and their photo... they are a lubrication consulting
firm and not a oil marketing department...

"Synthetics are derived by a different refining process to offer better performance owing to
their consistent molecular structure and purity."

Even if this was true, it would present itself as a viscosity difference (resistance to flow, remember?). You know what kind of viscosity you want and that's what you buy, synthetic oil won't flow any better at say 15 cSt than mineral at 15 cSt.

 

[BusyLittleShop]

Originally Posted By: Atesz792

Even if this was true, it would present itself as a viscosity difference (resistance to flow, remember?). You know what kind of viscosity you want and that's what you buy, synthetic oil won't flow any better at say 15 cSt than mineral at 15 cSt.


It is true because whats missing from your comparison is temp... in
order to establish a credible cSt number requires a Lab to heat the
oil sample to the standard 212ºF operating temp... but if you want the
Min to flow 15 cSt as the 15 cSt Syn it requires adding more heat to the
Min to equal the free flowing Syn... so if you test your 15 cSt Syn and
15 cSt Min at the standard operating temp of 212ºF you will note that
the Syn will flow more than Min due to the fact "Synthetics are
derived by a different refining process to offer better performance
owing to their consistent molecular structure and purity."

What we mean by 15 cSt is a quantity of oil was heated to a standard temp and the rate of
flow was recorded by a stop watch... this flow-rate is governed by resistance of the oil
flowing under gravity through the capillary tube, this test actually measures an oil’s
kinematic viscosity. The viscosity is typically reported in centistokes (cSt), and is
calculated from the time it takes oil to flow from the starting point to the stopping
point using a calibration constant supplied for each tube. This is how the engineers
know Syn flows more than Min of the same grade...

 

[Quattro Pete]

Originally Posted By: BusyLittleShop

What's important about a fully synthetic oil are the molecules which
are the same size and composition which decreases friction...

You do realize that vast majority of full synthetic oils still include some mineral components, for example as additive carriers, right?

 

[Atesz792]

So BLS you're practically saying that though mineral and synthetic pass the same diameter orifice in equal quantities at the same temperature in the same amount of time, one actually flows 'better' than the other. Really?

 

[BusyLittleShop]

Originally Posted By: Atesz792
So BLS you're practically saying that though mineral and synthetic pass the same diameter orifice in equal quantities at the same temperature in the same amount of time, one actually flows 'better' than the other. Really?




If you drop the temps to -35ºC its easy to see how equal grade Syn uniform molecules flow
better than Min inconsistent size molecules...

 

[Atesz792]

And now we're talking cold flow, VI and PP.
You're absolutely correct there, but the context was misleading.

 

[Ken2]

What does "synthetic" on an oil bottle mean?

 

[mlatour]

Some wet clutch applications don't work well with synthetics, sometimes makes for slip/grab clutch engagements.

Plain oil mineral Rotella-T 15w40 works very well in most motorcycle applications, even in high-revving (12K+ rpms)
250cc 4-stroke motocross race bikes and is cheap enough for preventative short drains intervals if you are one to change it as soon as it darkens.

 

[CT8]

Originally Posted By: Ken2
What does "synthetic" on an oil bottle mean?

It means the cost is higher.

 

[BusyLittleShop]

Originally Posted By: mlatour
Some wet clutch applications don't work well with synthetics, sometimes makes for slip/grab clutch engagements.


What wet clutches don't work well with synthetics???

 

[mlatour]

For sure in Yamaha YZ and YZ-F dirtbikes.

(YZ's are 2-strokes, oil in gearbox only, YZ-F's are 4-strokes, gearbox shares sump with engine)

By our local MX mechanic's many years of experience and myself and other YZ owners/friends,
synthetics in the gearbox of these bikes tend to make the clutches slip/grab at the most inopportune moments.

Replaced by either mineral JASO 10W40 or ATF (in the 2-strokes) is pretty much an instant cure.