Bob's Synthetic Q

["Al Powell" <APOWELL@agcom.tamu.edu>]

> I just changed the oil in my car (90 20V) and replaced it with the Mobil 
> 1 synthetic oil.  5w30 (winter coming and all...)
> when I started the engine, cold, it read the usual 5+ bar. After it 
> heated up a while, it read +-3bar at idle. Now I thought the whole damn 
> point of synthetics is they dont lose their viscosity over the 
> temperature range. Its no better than the old dino I used to use. am I 
> missing something here??? Did I forget to carry the 2?? :)
> 
> BOb

Hey, Bob - that's really not an issue at idle.  Synthetics resist 
viscosity change under use at high temperatures - idle pressure 
really isn't that relevant.  I was told some years ago that a good 
rule of thumb for minimum oil pressure is 10 psi/1000 rpm.  I use 
14.5 psi=1 bar as my standard "damn-it-broke-again-and-I-gotta-
convert-to-bar-to-figger-it-out" factor.  By that conversion, you 
have 43.5 psi of oil pressure at IDLE!!!!!!  Whoa!!!  That's as much 
as most detroit iron runs at full rpm!!  Since your idle is under 1K 
rpm, you're in good shape.  The benefit will come in reduced engine 
wear, better resistance to viscosity shift under use, better ability 
to dissipate heat, and (in turbos) resistance to caking on the 
bearings.  I believe you're ok.  :-)



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Al Powell                           Voice:  409/845-2807
Ag Communications                   Fax:    409/862-1202
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College Station, TX  77843-2112
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