With the New 9-3, we finally have something better than a calendar/odometer and more convenient than monthly oil analysis, to judge oil change intervals. The problem with using someone else's oil monitoring experience, such as Dick Church, is unless you follow him to work every day, your driving experience is most likely different. Absent a program of oil analysis to calibrate your particular needs, or an oil life monitor in the car computer, I'd think 6000 miles is more like it with synthetic, or 3000-4000 with conventional. I wouldn't go 10,000 without data.

John Lippis in Spokane has offered the first coherent argument that synthetic oil, even on longer drain intervals, can be superior to conventional oil on short drain intervals: bearing damage. Pumpability sets the low temperature viscosity reqirement, and then viscosity modifiers are added to meet high temperature requirements. But at high shear rates (that means inside the bearings) the viscosity (that means film thickness) tends toward the base stock viscosity, not the measured SAE number. ASTM has a spec for measuring this, and Red Line shows the results for a few oils. Synthetic oil base stocks have an inherently greater viscosity index, and so at 150C (as used in the ASTM test) the viscosity of the base stock for, say, 10W synthetic can be as high or higher than the base stock used for 20W conventional oils.

As for Mobil 0W40 (or other such oils), note that its use by Saab is in conjunction with the 2003 9-3 engine, which is different from the traditional engine. There is a lot of testing history with that oil in the new engine - it's the factory fill, and presumably has been used for extensive dyno and road tests. It may not have been used in the older engine, which may have larger clearances due to the different material (cast iron)used in the block.

More to come...

posted by 24.166.8...

http://www.saabclub.com

• oil change opinions. every 10,000 mi?!, Tom, Thu, 10 Oct 2002 21:55:59
  • NINES is working on this!, Stephen Goldberger, Sat, 12 Oct 2002 11:55:52 <-- Viewing This Message
    • Synthetic drain, Dick in Falls Church, Sun, 13 Oct 2002 11:33:00
    • Where's the coherent argument here?............, zeke, Sat, 12 Oct 2002 14:59:47
      • Oil analysis is the only real way to tell., Dave Westlake, Mon, 14 Oct 2002 09:08:23
  • Re: oil change opinions. every 10,000 mi?!, Ari , Fri, 11 Oct 2002 11:36:47
    • Still trying to figure it out?, Wayne, Fri, 11 Oct 2002 21:00:50
      • Oil problems, Ari , Mon, 14 Oct 2002 09:55:53
    • I'm in agreement with ya..., Dinger, Fri, 11 Oct 2002 15:38:12
  • Re: oil change opinions. every 10,000 mi?!, Dick in Falls Church, Fri, 11 Oct 2002 10:30:16
    • I like the idea of 10,000 mi oil changes with synth, KB88900T, Fri, 11 Oct 2002 21:57:34
      • Re: I like the idea of 10,000 mi oil changes with synth, Dick in Falls Church, Fri, 11 Oct 2002 23:27:34
    • Re: oil change opinions. every 10,000 mi?!, BHarvey, Fri, 11 Oct 2002 11:31:10
  • You cannot go wrong with 5K with synthetic, J, Fri, 11 Oct 2002 00:40:12
    • You're right, there is an oil war in 9-5!, Tom, Fri, 11 Oct 2002 10:10:04

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