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Posted by Joseph Meehan on June 19, 2005, 9:08 am
Vic Dura wrote:
>I just bought a new car last month. My previous car was a 1997 model
> and it specified 10w-40 motor oil, as had every car I have owned for
> the past 30 years. This new car (a 2005 Ford Focus) specifies 5w-20
> oil. I've since found out that 5w-20 has been pretty much standard for
> the past couple of years.
> Question: Why the apparent reduction in lubricating requirements?
That is not a reduction in the lubricating requirements. It is an
indication of a less thick oil. Less thick does not convert to less
lubrication.
> I
> can understand that theoretically the 5w requires less power to pump
> and therefor *might* result in some mileage improvement; but the high
> temp reduction from 40 equivalent to 20 equivalent doesn't make sense
> to me.
> What am I missing?
You are right about the reduced pumping force, but that applies to the
hot measure (large number) as well. It also means the engine has to use
less energy to move pistons and other engine parts all of which mean a
little higher mileage.
It does not stop there. Today's engines are not designed like older
engines. The parts are made with closer tolerances so the heavier oil would
not lube or cool (cooling is a function of oil as well) them as well.
Stick with what the manufacturer recommends. If you want better oil,
try synthetic. Of course be sure to use nothing by synthetic if the
manufacturer calls for it.
The lubrication and other specifications are part of that letter after
the "S" You can use any oil rated equal to the "S" number specified or
higher. ("C" number for diesel engines).
--
Joseph Meehan
Dia duit
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> and it specified 10w-40 motor oil, as had every car I have owned for
> the past 30 years. This new car (a 2005 Ford Focus) specifies 5w-20
> oil. I've since found out that 5w-20 has been pretty much standard for
> the past couple of years.
> Question: Why the apparent reduction in lubricating requirements? I
> can understand that theoretically the 5w requires less power to pump
> and therefor *might* result in some mileage improvement; but the high
> temp reduction from 40 equivalent to 20 equivalent doesn't make sense
> to me.
> What am I missing?