Viscosity. I need help.

[leebae]

I guess I just do not understand. I just read the article on oil basics written by Dr. Haas. It makes perfect sense that regardless of ambient temperature a 0w-30 or 5w-30 is always the better choice over a 10w-30.

My dilemma. My Volvo owner manual clearly recommends the use of 10w-30 in lieu of 5w-30 in areas/regions where the ambient temperature frequently exceeds 86 degrees.

Does Volvo simply not understand? Why would they not just recommend a 5w-30 regardless? I just advised my mechanic (about 2 OCI's ago) to start using GTX 10w-30 in lieu of the 5w-30 I was previously using based solely on the recommendation of the owners manual.

Should I switch back to GTX 5w-30????

 

[leebae]

What about my wife's Chrysler Pacifica? It is printed right on the oil filler cap (10w-30). Is 5w-30 the better option? I have not looked at her owner's manual.

 

[vronline]

For you, being in GA, I doubt it's going to be much of an issue. However, the thinner oil may give you a benefit at start-up.

In my opinion, 5W-30 is the better option.

 

[TimVipond]

If it helps you sleep any better, Amsoil recommends their 0W30 for both those applications.

 

[Pablo]

There are a lot more serious things to worry about. I honestly doubt 10W-30, in summer, in Georgia makes a heck of a lot of difference vs. a 5W-30.

Without going to deep and causing more worry, some of the anti 5W-30 is based on old oil lore. And there was some basis in fact 20+ years ago or so. The oils just didn't hold up as well. Car manufacturers are often years behind in lubrication on the year the car was designed - then you need to factor in; even your "new" car is coming up on 6 years since BUILD date, and add a few more years since specification date.......

 

[leebae]

I have seen that recommendation in the product application section of the website. It also states to use 5w-30 in temps below 86 degrees in lieu of the 10w-30 products. This seems contradictory. Why suggest 0w-30 or 10w-30 and then spec 5w-30 in lower temps?

 

[TimVipond]

Pablo is right. Just look how long it took Ford to back recommend 5W20 for their cars that they recommended 5W30 for.

 

[TimVipond]

Leebae,

Amsoil gets their vehicle recommendations from a 3rd party. Those recommendations are listed in black type. Then Amsoil evaluates it and decides which of the Amsoil products are the best recomendations and that they will warranty. Those recommendations are in the blue type with product links.

 

[leebae]

Good to know. It sounds as if my choice to use a 10w-30 in lieu of the 5w-30 was incorrect. I will switch back on the next OCI. That is only about 250 miles away.

 

[TimVipond]

Did you notice any differences in the way your car runs with the same brand different viscosity oils? Fuel mileage, cold start noises, etc?

 

[Pablo]

OK - there are couple other things blurring the lines....

1) Remember XW-30 is not one viscosity at 100°C, it's a specification range.
2) Same for the XW part, or rather it's a cold temp -30°C/-35°C/etc specification limit. Some oils just flow a LOT better than other oils at cold temps. A 10W-30 PAO or Ester synthetic could be used in a cold climate, where a 5W conventional would barely be pumpable.
3) Combining this info, you really need to know the viscosity curve, or rather compare viscosity temperature curves of individual oils, vs comparing the SAE given names of oil (say 5W-30 vs. 10W-30)

If you grasp these concepts, you won't get so worried about 5W vs. 10W, which is just a simplified system for the masses.

For example I'm going to run Amsoil 15W-40 full synthetic HDEO in my 1996 850 Volvo*. Yes I know it's viscous, but it flows better in cold than many/most old style dino 10W-40's. Would I run a conventional 15W-40 in winter? Heck no.

*Why am I doing this you might ask? Let me just say I scored some 2.5 gallon jugs for $7.49 each.

 

[G-MAN]

Quote:

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*Why am I doing this you might ask? Let me just say I scored some 2.5 gallon jugs for $7.49 each.

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Just rub your juicy Amsoil insider deals in our faces, why dontcha?

 

[wgtoys]

"regardless of ambient temperature a 0w-30 or 5w-30 is always the better choice over a 10w-30"

While that MIGHT be a reasonable rule of thumb, when getting down to the details it all depends. Not too many years ago many 5W-30 oils often sheared out of grade over time more rapidly than many 10W-30 oils. Today that is less common, but it is impossible to draw any certain rules about the situation. This is the reason some owners manuals specifically warned against using 5W-30 oils. In years gone by Volvo and others also specifically said not to use 10W-40 oils in part because some of them had terrible shearing problems over time. As late as 1996 Volvo was still recommending 15W-40 in US market vehicles for summer conditions.

All that said, in a Georgia summer it isn't going to matter a bit if you choose a 5W-30 or 10W-30 oil of good quality and follow the severe service mfg. interval.