Multi-weight oils are designed to maintain their viscosity through a wide range of temperatures. This is achieved through using compounds that react to heat in the opposite way that oil does. (Oil thins as it gets warmer, these compounds cause the oil to thickeng as it warms.) Thus, 10w30 has the viscosity of a 10 weight oil when cold and 30 weight oil when hot. The wider the range, the greater the amount of additives that are necessary. Although this is good if your car will experience a wide temperature range, it is not good otherwise. This is because the additives are prone to shear stress (break down due to mechanical shearing in the engine) and do not lubricate as well as oil. Thus, stick with the smallest range that will work in your climate. For example, 10w30 should provide excellent range in Atlanta for most of the year. A 0w30 would be needed in Alaska in the winter. A higher weight, 15w50 might have some advantages in Arizona (or possibly Atlanta) in the summer.

I don't know the actual viscosity values, but from the old days of single weight oils, I can tell you that hot (usual operating temp) 30 weight oil has a similar viscosity to room temperature (~70 degrees) 10 weight oil. At 0 degrees the 10 weight will still flow well, the 30 weight begins to flow like molasses. When hot (summer engine operating temperature), 10 weight oil is so thin it begins to lose it's lubricating ability.



posted by 162.119.64...

• Comments on new Mobil1 formula? and difficult ques., AP, Tue, 23 Apr 2002 18:44:55
  • Re: Comments on new Mobil1 formula? and difficult ques., Kevin K , Wed, 24 Apr 2002 10:54:20
  • oil viscosity - small part of a very long story..., JimBlake , Wed, 24 Apr 2002 10:25:45
    • Regretably, thet 0F spec is not used ..., Kevin K , Wed, 24 Apr 2002 10:59:04
      • showing my age..., JimBlake , Wed, 24 Apr 2002 12:52:30
  • MOBIL SAYS.....about viscocitys, AP, Tue, 23 Apr 2002 21:38:39
  • oil viscosity..., jcb, Tue, 23 Apr 2002 19:46:41 <-- Viewing This Message
  • I just use 10W30 M1 here in ATL in my '89 SPG, RS , Tue, 23 Apr 2002 19:32:14
  • 10w30 - if you are running 3/4 of the temp gage, KeithG, Tue, 23 Apr 2002 19:25:56
    • Re: 10w30 - if you are running 3/4 of the temp gage, AP, Tue, 23 Apr 2002 21:26:21
      • AC clutch, JimBlake , Wed, 24 Apr 2002 09:45:21
        • good point, i forgot its got its own belt. n/m, AP, Wed, 24 Apr 2002 22:15:17
  • 10W30 here.., JonG, Tue, 23 Apr 2002 19:25:17
    • Re: 10W30 here.., Kirk, Thu, 25 Apr 2002 00:36:45

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