Oily stuff - 5W20

[Huw Powell]

John is correct.

The idea of looking at the numbers on oil and "deciding" whether or not 
to use it makes no sense.

Engines are built to certain tolerances and require certain fluids to 
function properly.

In the case of oil, there is a viscosity range recommended (which may 
vary slightly depending on conditions), from a "cold" end that allows 
sufficient flow for lubrication at start up to a "hot" end that 
maintains enough viscosity for adequate pressure to be developed at 
"running" temps.  Keep in mind that "running" temps are pretty much the 
same no matter how (reasonably, like >= -40 deg) cold the ambients are.

Just because a new weight range turns up on the shelf doesn't mean it's 
a new good thing for your engine.

The "standard" used to be 10W40, with a few deviations, and a few 
requirements for synthetics.

The standard for the last couple of decades has run towards 5W30, with 
many calls for 5W20, 0W20, etc., often requiring OEM/dealer sourced oil 
coming in the last decade.  These engines have far tighter tolerances 
and thus build plenty of pressure with the thinner oil, saving energy - 
and also, well, having tighter tolerances.

These simply are not correct for our cars.  If you aren't sure, check 
your owner's manual and use either what it says, or try something 
slightly thicker if you are consuming a lot (> 1 qt/1000 mi, or even >1 
qt/tankful of fuel).

I like 5W50 synthetic for my 90Q - easy cold starts, no fears of it 
getting too thin when I am in "oil-cooled" mode.

- Huw

On 12/3/2014 11:46 PM, John Larson wrote:
> On 12/3/2014 2:32 PM, Tihol Tiholov wrote:
>> To keep list traffic going, here's a general question. Anyone with
>> thoughts, experience, etc. re: this oil? Isn't it too narrow a temp.
>> range,
>> esp. for the Graet White North? I don't, nor intend to use it, just
>> curious, since it's taking over the shelves at FLAPS.
>>
>> Tihol
>>
> It's important to remember that modern "thin" oils are required for use
> in modern engines.  Tolerances are tighter, oil passages are smaller,
> and the engines are designed to utilize thinner oils to aid in fuel
> economy.  Older designs, such as all the I5 engines and nearly all their
> contemporaries don't do well with thinner oils because the passages are
> relatively large and clearances are loose. The results of using oils
> made for the newer designs are lowered oil pressure, and most likely
> increased oil consumption.  Porsche, as well as Mercedes, use 0w20 as a
> factory fill.  Scary, huh? Knowledgeable techs and shops put 5w20 in 'em
> ...
>
> John
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