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"multigrade" oil is a non-newtonian fluid, meaning that the viscosity changes depending on the shear velocity. The big number in the oil viscosity rating is a measure taken at 100C and at low shear velocity. The OG9-5 (and T-7 9-3) runs its oil at more than 100C, and the shear velocity in the bearings is high (and apparently very high in the case of the guy who keeps "burning up" engines). You need to look at HTHS, or high temperature, high shear viscosity. Saab's European oil recommendation requires that it be greater than 3.5 cSt. Most 5W40 and 10W40 synthetic oils have a HTHS rating of more than 4 cSt. Most XXW30 oils have a rating of less than 3.5. Look at the European rating - if it's ACEA A5/B5 (or A1/B1), then it is less than 3.5. Mobil 1 0W40 has a rating of 3.6; Catrol 0W30 has a rating of 3.5.

I would not use either one in a T7 9-3 or 9-5, but rather, as recommended here by others, 5W40 or 10W40 fully synthetic. 15W50 is a good alternative for high loads (towing, racing) and high temperatures. PE Polyol Ester base stock oils (Red Line) have inherently high HTHS ratings - their 10W30 oil, for example, has a HTHS rating of 3.8, higher than Mobil 1 0W40 (but not as high as Mobil 1 10W40), and if force at gunpoint to use 10W30, that's what I would select.

posted by 24.165.162...

• Saab friends recommend I use 10w30 in my aero, turbostud, Thu, 2 Jun 2011 05:52:38
  • Oil viscosity 101 - er, maybe 401...-, Stephen Goldberger, Fri, 3 Jun 2011 06:22:50 <-- Viewing This Message
    • Dont use mobil 0w-40 ??, RMinNJ, Fri, 3 Jun 2011 09:05:51
      • Er, nothing against M1 0W40, but..., Stephen Goldbergers, Sat, 4 Jun 2011 04:53:47
        • Re: Er, nothing against M1 0W40, but..., RMinNJ, Sat, 4 Jun 2011 07:33:39
    • Re: Oil viscosity 101 - er, maybe 401...-, SG, Fri, 3 Jun 2011 08:08:35
      • Right..., Stephen Goldberger, Sat, 4 Jun 2011 04:58:17
  • 301,000 miles w/ primarily 5W/40, MI-Roger , Fri, 3 Jun 2011 03:25:51
    • With 300K in 11 years, nothing really matters, SWEDECAR , Sat, 4 Jun 2011 08:45:18
    • 190,000 mi with 10k oil changes on 0w40, dmz789qqq, Fri, 3 Jun 2011 09:11:22
      • With a TBN of 11.8 the 0w40 may be good for 10K....., MI-Roger , Fri, 3 Jun 2011 10:40:33
  • the classic is a totally different beast!, James, Thu, 2 Jun 2011 16:24:20
  • heh, Les_H, Thu, 2 Jun 2011 08:30:23
  • 2+2=5?, saabsince 93b , Thu, 2 Jun 2011 08:25:51
  • Re: Saab friends recommend I use 10w30 in my aero, Buck60, Thu, 2 Jun 2011 08:14:27
  • Anecodtal evidence, Noel, Thu, 2 Jun 2011 06:58:41
    • Mobil 1 0W-40 only n/m, AdamSAAB2kAero , Thu, 2 Jun 2011 07:00:37
  • Huh, Paul Roberts, Thu, 2 Jun 2011 06:13:16

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