Which Oil Grade do I Need?

run what you are comfortable with

take into consideration that your engine oil temp can run at or up to 250* on a long pull and, or a hot day.

TucsonJim wrote:
I'd discuss it with the service manager at your local dealership. I had the same quandry with my '13 Ford. My service manager conviced me to to with the lighter viscosity oil.

We are full time and travel all over the USA. My manual and oil fill cap clearly states to use 5w40 in my diesel. Yet, I've had dealers question my use of this oil. I pull out the manual and they act surprised. Had two dealers tell me I'm the only customer that ever asked for the 5w.... Lesson, don't trust the dealer, do what the manual tells you based on your driving conditions.

JustLabs wrote:


Nonsense...

I've looked at hundreds of UOAs over the years and its rare to find a 5w-30 that doesn't shear.

You need to word this statement better.

ALL OILS SHEAR. Additives naturally "break down" while in use and can change viscosity. This is 100% normal.

My point has been, that it's rare for automotive engine oils to shear OUT OF GRADE during normal, recommended intervals. Some of the few reports that do show an oil out of grade, often have a higher than normal gasoline content, changing the oils viscosity.

I have benn doing some research, and found a lot of interest in 0w20 and 0w30 oils....supposed to be designed with higher quality base stocks....

I am thinking about going to a 0w30 next change....royal purple??

RinconVTR wrote:

Charlie D. wrote:

JustLabs wrote:
I'd use a 5w-20.

The 5w-30 will probably shear out of grade and end up as a 5w-20 anyways.

With that logic wouldn't the 5w-20 shear also and lower the viscosity?

There is no logic with those types of statements, nor facts. This statement then assumes a Xw-20 will sheer to a Xw-10!

Anyone who keeps up with UOA's (used oil analysis) reports on the web knows AND does their very own...knows very few motor oils sheer out of grade in automotive engine applications.

Nonsense...

I've looked at hundreds of UOAs over the years and its rare to find a 5w-30 that doesn't shear.

Charlie D. wrote:

JustLabs wrote:
I'd use a 5w-20.

The 5w-30 will probably shear out of grade and end up as a 5w-20 anyways.

With that logic wouldn't the 5w-20 shear also and lower the viscosity?

For the most part no.

5w-20 is made with better base stocks and has less viscosity index improvers. 5w-20 is less prone to shear.

jus2shy wrote:

Also, Viscosity ranges do not overlap. A 30 weight oil is noted as being between 9.3 to 12.49 CsT at 100 degrees C. A 20 weight oil is noted as between 5.6 to 9.29 CsT at 100 degrees C. No overlap, and this is the SAE's definition of the oil grades.

.

Of course SAE specs do not overlap.

Actual measured values can and sometimes do.

RinconVTR wrote:

Charlie D. wrote:

JustLabs wrote:
I'd use a 5w-20.

The 5w-30 will probably shear out of grade and end up as a 5w-20 anyways.

With that logic wouldn't the 5w-20 shear also and lower the viscosity?

There is no logic with those types of statements, nor facts. This statement then assumes a Xw-20 will sheer to a Xw-10!

Anyone who keeps up with UOA's (used oil analysis) reports on the web knows AND does their very own...knows very few motor oils sheer out of grade in automotive engine applications.

There is also a lot of variation of virgin oils, where 5w-20's are actually within 5w-30 viscosity range. This means nothing except to tell us how close the numbers really are!

I read the oil reports for a fleet of hundreds transit buses. When selecting oil change intervals, viscosity decrease (or increase in some cases) are a determining factor (but not the only one). All oils sheer over time and after about 10,000 to 12,000 miles we've basically sheered from a 40 weight oil down to a 30 weight oil. This is also with very very little fuel dilution, so it isn't due to fuel dilution. Some fleets pass a bit of soot which increases viscosity, but that tends to be our older buses.

Also, Viscosity ranges do not overlap. A 30 weight oil is noted as being between 9.3 to 12.49 CsT at 100 degrees C. A 20 weight oil is noted as between 5.6 to 9.29 CsT at 100 degrees C. No overlap, and this is the SAE's definition of the oil grades. The "W" weights are only applicable at cold start-up. Once the oil is warmed to operating temperatures, the 100 degree grade is what matters which is the latter number (20 or 30 in this case).

However, most oils for your every day application though will not sheer out of their weight if you follow manufacturer recommended oil change intervals (in fact, most could go longer because of their duty cycle but the manufacturers would like to void your warranty if you do that). However the engineers wanted a buffer of some sort, either a thicker layer of oil between rotating assemblies, or they may worry about sheer since the motor could be revving and running harder than it typically would when tooling around town or the freeway with a lighter load. Unfortunately, we're only speculating at this point and only a Chrysler engineer can truly answer this question.

I went from 30 to 20w in my Prius, and still get 52-54mpg, didn't make a difference, so I stayed with the 30w, my wifes 2013 Prius uses 20w though, I don't think the difference is much, and you'd think on a small engine like these it would make more of a diff..

Charlie D. wrote:

JustLabs wrote:
I'd use a 5w-20.

The 5w-30 will probably shear out of grade and end up as a 5w-20 anyways.

With that logic wouldn't the 5w-20 shear also and lower the viscosity?

There is no logic with those types of statements, nor facts. This statement then assumes a Xw-20 will sheer to a Xw-10!

Anyone who keeps up with UOA's (used oil analysis) reports on the web knows AND does their very own...knows very few motor oils sheer out of grade in automotive engine applications.

There is also a lot of variation of virgin oils, where 5w-20's are actually within 5w-30 viscosity range. This means nothing except to tell us how close the numbers really are!