Mobil 1 oil weight

Tue May 1 22:17:42 EDT 2007

Geez...I signed off twice on this thing.  Comments in text below first 
sign off...

Steve Marinello wrote:
> I'll lean toward ensuring remaining film strength, based solely on 
> personal experience.  Three I5 turbos that blew or burned oil on the 
> light stuff, and one (stock S6 AAN) that fired up with a shrieking turbo 
> and valve clatter after sitting five days and thereafter shrieked on 
> boost until I got the light oil out and 15W50 in.  The valve clatter in 
> the urq (driven rarely) was so bad that I didn't put 100 miles on it 
> before I changed the oil out.  The RS2'ed S6 avant just burned oil and 
> got the worst mileage it ever had...which the S6 sedan did, too.  I have 
> to believe, despite over extended statements of Dr. Haas, that more 
> damage/wear was done to all three engines in the time they had that oil 
> in them than in all their previous miles.  My guess; the light stuff 
> drained out of the hot, turbo'ed engines to completely and there wasn't 
> sufficient film protection remaining on the engine and turbo bearings or 
> at the head/valves at startup.
>
> Better base stocks are only better based on the tests chosen.  Doesn't 
> really say much about real world for a given car and engine, much less a 
> particular owners driving characteristics and habits.
>
> I had a 1608 cc Fiat 124 Sport Coupe that I sold with 178k on it that 
> had only seen 20W50 GTX...except for the summer when I worked near the 
> Salton Sea/Mexican border and ran 60 weight Valvoline racing oil (hey, 
> it was 112F at midnight!).  When sold, compression in all cylinders was 
> at the top0 of new spec.  The engine had hot street cams, dual dual 40mm 
> Webers and a free flow exhaust.  It never burned a drop of oil and 
> embarrassed various P-cars with its' power and customized suspension and 
> did lots of canyon runs and got 30+ mpg cruising I5 at 75-85 mph during 
> many super slab blasts from Stanford to L.A.  All on that much maligned 
> dino oil and 3000  mile oil changes.
>
> Find an oil that works and change it when it needs it.  For NA cars, 
> unless they are seriously hi performance, I don't see the need for 
> synthetics, unless you live down here in the humid gulf where moisture 
> finds its' way into everything and do lots of stop and go traffic and 
> are lazy about changing oil.  Synthetic, lighter weight, for newer tight 
> tolerance turbo engines.  Same rules apply about finding an appropriate one.
>
> FWIW, the modified Alfa 2 liter coupe I had at the same time didn't run 
> nearly as well on GTX.  Its' engine preferred the viscosity 
> characteristics of Valvoline 20W50 racing, so that's what it got.  Seems 
> someone several years ago posted that their S4 (C4) seemed to prefer 
> Amsoil 15W40 Diesel oil. Had an Amsoil tech tell me he wasn't surprised 
> and that he thought it was one of the best oils they made.  It worked, 
> and I hope he's still using it.  I may have to give it a try, since 
> ordering it may be just as easy to get an oil I want right now.
>
> If 0W30 works for you, Grant, great..really!  If you do end  up with 
> engine problems however, do let us know.  Ameer, whatever you decide to 
> run is fine with me.  Again, let us know how it works out.  I have three 
> cars and two of them don't see lots of duty anymore, so I will make sure 
> they have higher vis synthetic in them as they sit here in Houston 
> humidity and will TRY to make sure I fire them up and take them out at 
> least once a month.
>
> Steve
>
> Grant Lenahan wrote:
>   
>> I saw this earlier, but didn't have time to respond intelligently - you 
>> raise important issues, although you dont sway my conviction. let me 
>> explain why.
>>
>> Most people agree with you.
>>
>> Historically, oil and motor manufacturers agreed with you.
>>
>> But 3 things have changed:
>>
>> 1.) think oils can be made from much better base stocks. Most 
>> synthetics begin with the higher weight base (eg: 40), and flow well 
>> naturally. Most dino oils  started with the lower weight (e.g.: 0) and 
>> then added VI improvers to meet higher temp demands.  These VI 
>> improvers dont work all that well (low VIs) and wear out, leaving you 
>> with thin oil.  Synthetics dont.
>>   
>>     
> Which means that they last longer and don't have to be replaced as 
> often.  But, 'improvers" with dino oil can still meet most hi temp 
> demands  at a much lower cost point than synthetics.
>   
>> 2.) Research has shown that to maintain oil flow, and thus good 
>> lubrication, almost all oils are too thick until operating temperature, 
>> at least, is reached. read Dr. Haas' articles (all 10 of them) before 
>> countering this.
>>   
>>     
> Counter what?  That's why multi-vis oils were developed.  Nothing new or 
> shocking at that.  Technology advances and we get better at addressing 
> that point as time moves on.
>   
>> 3.) Further research has proven the old farmers' tale true. A paper 
>> from the last SAE conference in fact.  >90% of all engine wear occurs 
>> during startup and cold running. Not just "dry cranking", but 
>> insufficient flow to meet the demands of rpms above idle.  This can 
>> occur very, very low.
>>   
>>     
> Again, the reason for multi vis oils.  Your premise is that you will 
> always have better flow/fluid transport with lower vis oils.  That isn't 
> true.  There has to be a balance, which is addressed for a particular 
> engine and oil passage dimensions by a particular viscosity.  We are not 
> pumping in a completely filled and closed system.  The oil pump as to 
> effectively pick up and move that fluid.  It's a whole lot easier to 
> pick up a fluid with some minimal/substantial viscosity than to pick up 
> and move something with a viscosity like water.  Unless the oil in use 
> has the properties necessary to maintain a minimal film strength for the 
> time period the engine is expected to be shut down, after operating 
> under the conditions and temperatures under which it is shut down, it 
> will cause more damage to the engine than a short transient oil 
> starvation before pressure comes up.  Again, it's related to the design 
> of passages and tolerances in a given engine.  Tests with laboratory 
> standards, or on one particular type of engine don't necessarily relate 
> to another given engine and (although I hate absolutes and think that 
> this whole discussion is caught in trying to apply results globally in 
> absolute terms) I would venture to say, ABSOLUTELY do not apply to all 
> engines.  That doesn't mean the findings aren't valid; it just means 
> that there are other factors modifying their validity for a particularly 
> case.
>   
>> The last two say the industry was always wrong, if well intentioned.  
>> Long held beliefs change slowly.
>>
>>   
>>     
> It doesn't say the industry was wrong!  It just said they addressed the 
> problems by a different means with the technology of the times.  We knew 
> that 95% or engine wear occurred at start-up when I was a kid...and I'm 52!
>   
>> You are very right that older motors have larger tolerances. You are 
>> also right that they require a thicker film to fill this void, maintain 
>> pressure and protect. But this can happen two ways:  1) higher flow, 2) 
>> thicker oil.  With insufficient pressure and pump volume, thicker oil 
>> wont solve the problem.  Dr. Haas shows this is often true below 100 
>> degC.
>>   
>>     
> Look at what you said, "with insufficient pressure and pump 
> volume"...There are the proviso's...do you think Porsche, Audi, Ferrari, 
> MB ensured that there oil pumps were designed to provide the pressure 
> and flow requirements for the oils specified?
>   
>> I dont know where the line is drawn. The only way to end this 
>> conclusively is to monitor both temperature, and flow, and pressure 
>> simultaneously on various motors. That would be a very worthwhile 
>> research project.  It might even cut list volume by 80% :-)
>>   
>>     
> Agreed, but you have to include the aforementioned shut down temperature 
> and static time and measure film strength and thickness, too.
>   
>> Would I go a bit thicker in an older I5? yep. But I used 5W30 (M1) in 
>> my I5s with great results.  Dr. Hass' research and calculations show 
>> that these oi;ld (5w30, ow40) are too thick for modern motors ( at 
>> least above idal),. So, using your own logic, they may in fact be 
>> perfect for older ones. Without data its just speculation.
>>   
>>     
> Got my data...3 out of 3!  Not a coincidence, in my experience.
>   
>> Bottom line is more damage is done by thick oil in cold engines than 
>> thin oil in hot ones.
>>   
>>     
> Again, depends on what's left on the engine surfaces and how well it 
> protects relative to initial oil 'starvation'.  Just 'cause you got thin 
> oil doesn't mean it will pump efficiently through the engine at startup.
>
> I just remembered a screw-up of mine with the Fiat after the summer down 
> near the border.  I hadn't changed the oil back to 20W50 after heading 
> back up to school in the fall.  And time just kept slipping, because I 
> rode my bike and the car basically sat there with only occasional 
> use...for three months.  Just didn't get around to changing it because, 
> heck, it only had 1500 miles on it.  Came Thanksgiving and a spur of the 
> minute ski trip to Mammoth and an unexpected blizzard.  After four days, 
> dug the car out, remembering the race oil as we dug.  I was sure it 
> wouldn't turn over.  But it did...and fired each cylinder so that you 
> could hear it and see the engine turn with each pulse.  The damn thing 
> just kept going and eventually started to run faster and faster and 
> warmed up and we were off, everyone shaking their heads in disbelief at 
> what had happened...and at how the car nut could be so stupid.  That 
> racing oil had helacious film strength, but still a low enough viscosity 
> to allow the engine to turn at about 20F.  Granted, that's not at -5F, 
> but it was enough so that, starved as the engine was for circulating 
> oil, it was able to function.
>
>
> Boy, that was a ramble.  That's what happens after listening to a Jr. 
> High School band concert....
>
> Steve
>
> Ol' Fart ex-Engineering Prof and some kinds of fluid flow specialist
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