Mobil 1 oil weight

[Grant Lenahan]

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.

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.

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.

The last two say the industry was always wrong, if well intentioned.  
Long held beliefs change slowly.

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.

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% :-)

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.

Bottom line is more damage is done by thick oil in cold engines than 
thin oil in hot ones.

Grant



On Apr 30, 2007, at 9:47 PM, John Larson wrote:

> Grant wrote:  "Guys - ignore those charts.
> Think oil flow.
> Think about the distribution fo time from cold to hot.
> Read the viscosity ratings at 40 and 100 deg and extrapolate.
> Those charts are obviously wrong.  Note also how every manufacturer is 
> moving to thinner and thinner oils.  We're learning, slowly."
>
> Grant
>
> I dunno what happened to my post this morning, but I'll repeat and 
> elaborate on the thoughts here.
>
> It's true that most, if not all, automakers are going to the use of 
> thinner oils.  This is an effort to obtain reduced friction in their 
> search for improved fuel mileage.  In doing this, they've redesigned 
> their engines with reduced clearances and smaller oil passages.  
> Modern engines have shrouding and insulation to stabilize 
> temperatures, special coolants, and are made of new and exotic 
> materials.  I believe the engine to which the original post referred 
> (correct me if I'm wrong) is an '85 5KT, hardly a "modern" power 
> plant.  It's a cast iron block with a plain-jane aluminum head, 
> something that's been in common use since the mid '50s  It was 
> designed to use a pretty early generation multi grade oil of 
> substantial viscosity.  Mostly 20w50 in weather common in much of the 
> US, and maybe 5w30 or 10w30 in severe weather.  Beginning in the late 
> '80s, some Japanese cars (4 cylinder SOHC Mazdas, for sure) required 
> 5w30, and many other manufacturers began to see this as a way to 
> reduce friction and improve fuel economy.  It's interesting to note 
> that the aforementioned Mazda 1600cc engines exhibited horrendous 
> lifter clatter when 20w50 oil was used!  It would appear it couldn't 
> get through the passages and the lifters ran dry.
> Audi began specifying thinner oils sometime in the time of the C4.  
> Thinner being 10w30 or 10w40.  20w50 was still recommended for 
> sustained high speed driving in hot weather.  With the advent of the 
> 1.8T in the A4 and other VAG vehicles, 5w30 synthetic was the oil of 
> choice, then it was changed to 5w40. Late MBs use 0w20, as do some 
> American made cars.
>
> My point is, cutting to the chase, you risk SIGNIFICANT engine damage 
> running oil other than the weights recommended for specific engines of 
> specific model years. First as an enthusiast, then a professional tech 
> for a total of right at 47 years, I've seen oils change for a LONG 
> time.  Running light oils in engines designed for heavier oils can, 
> and will, result in reduced oil pressures at any given temperature.  
> In air cooled engines, where I started out, this translates to an 
> inability to remove heat, effectively reducing the life of the engine. 
>  Toasted bearings, rings, valves and seats were a direct result.  
> Water cooled engines, as well as turbochargers, depend on oil to both 
> lubricate and to help get the heat away.
> That's why we use oil coolers, a once rare component that has become 
> an integral part of most engines and their temperature management 
> infrastructure.
> Do yourselves a favor.  Consider carefully the thinking of the 
> designers of the engine you have.  Sure, there have been steady 
> improvements in oils, but the viscosity required when YOUR engine was 
> designed isn't necessarily affected by what the new oils offer.  Most 
> of us accept that running high octane fuel in an old engine made to 
> run on low octane fuel is a waste of money, and that running lead 
> additive is a waste of money with hardened valve seats, so why the 
> resistance to running oil viscosity recommended by the manufacturer?  
> Is your personal engineering department better than theirs?  Is 
> anything you see on the internet infinitely more trustworthy than the 
> recommendations of the automakers?  I deal with this cr*p every day.  
> Bozo comes in with a part somebody said would make his car faster, 
> louder, quieter, more fuel efficient, cooler looking, or whatever, and 
> he doesn't want to hear it won't fit, it won't work, it'll wreck his 
> engine, it'll make it fail the smog check. After, what do I know, 
> other than the truth, the law, and reality?  BTW, those fuel line 
> magnets STILL fly off the shelves at Harbor Freight!
>
> Think about it.  Sorry for the long rant.  John
>
>