Manual recommends 5W30 year-round in Impreza

[David Buchner]

Subaru says, in the 2002 Outback Sport manual, through the classic
awkward translation:

*) 5W-30 is preferred.

....for anything from like -40F to 100F. Basically, it goes through all
the regular stuff about oil, and then says to just use 5W-30 all the
time unless you're lost in the desert pulling a trailer.

Why do they recommend this?

Do owners follow this, or just use 5W-30 in the winter and 10W-30 in
summer just like other cars?

I asked at our dealer, and the mechanic says they pay no attention to
this, and change winter/summer oil just like always. I've been following
the instructions so far, running Castrol Syntec 5W-30 year round. I like
not having to shuffle around my spare quarts from season to season.

Thoughts?

 

[Edward Hayes]

Most ALL manufactures call for 5w30 year around unless trailer pulling in
the Saudi desert. New fords and Honda demand 5w20 now. Lighter oil cools
better, lubricates precision close tolerance parts better and reduces wear
during the warm up.

 

[Carl 1 Lucky Texan]

Lighter oil may also drain from parts faster exposing more metal-metal
surfaces, allow more blow-by, and suffer breakdown at high temps.

many models here in the states that say use a light weight oil,
recommend a heavier weight when sold overseas.

I think the CAFE rules are the primary driving force behind the
stateside switch to lighter oils - there is a small but measurable
increase in gas mileage. Still, it may only mean you get 250K miles
instead of 300K miles of engine life - who knows?

Carl
1 Lucky Texan

 

[y_p_w]

Lighter oil may also drain from parts faster exposing more metal-metal
surfaces, allow more blow-by, and suffer breakdown at high temps.

many models here in the states that say use a light weight oil,
recommend a heavier weight when sold overseas.

My WRX manual says that 30, 40, 10W-50, 20W-40, or 20W-50 can
be used for extremely hot climates or for towing. I'm not sure
where to find 10W-50 or 20W-40 though. I haven't seen a
manufacturer recommend 10W-40 for normal use in a while, like in
the Subaru manual. Mostly I've had dealers say to use 10W-40 if
the car starts using oil.

Also - don't EP additives cling to metal and protect during
startup?

I think the CAFE rules are the primary driving force behind the
stateside switch to lighter oils - there is a small but measurable
increase in gas mileage. Still, it may only mean you get 250K miles
instead of 300K miles of engine life - who knows?

I've heard that lighter multi-weight oils can get to places
heavier oils can't. Still - the engine is probably tolerant of
a wide range of oil weights.

 

[Rick Courtright]

Why do they recommend this?

Primary reason is CAFE rules for gas mileage...

Do owners follow this, or just use 5W-30 in the winter and 10W-30 in
summer just like other cars?

Older Subies had a recommendation on 5W-30 to avoid prolonged highway
driving when using 5W-30, and recommended 10W-30 for warmer conditions
(judging by my '90 owners' manual.) I think they were telling us the
same thing Castrol used to post on their website: lighter oils are
better for fuel economy, but don't protect as well as heavier oils under
heavy use. That bit of info disappeared from Castrol's site several
years ago--I don't know if it became obsolete, or politically
incorrect?????

OTOH, a buddy bought a Ford Super Duty p/u with the V-10 a couple of
years ago and has been running 5W-30 (Mobil 1) since break-in and he
spends a lot of time in the desert, while we've been running 5W-30 in
the g/f's Honda Civic since new (we live in a rather warm area of SoCal)
and neither vehicle has shown any ill effects. But they don't have the
345k miles my Subie does, so it waits to be seen what the long term
effects will be.

Rick C

 

[y_p_w]

David Buchner wrote:




Primary reason is CAFE rules for gas mileage...




Older Subies had a recommendation on 5W-30 to avoid prolonged highway
driving when using 5W-30, and recommended 10W-30 for warmer conditions
(judging by my '90 owners' manual.) I think they were telling us the
same thing Castrol used to post on their website: lighter oils are
better for fuel economy, but don't protect as well as heavier oils under
heavy use. That bit of info disappeared from Castrol's site several
years ago--I don't know if it became obsolete, or politically
incorrect?????

OTOH, a buddy bought a Ford Super Duty p/u with the V-10 a couple of
years ago and has been running 5W-30 (Mobil 1) since break-in and he
spends a lot of time in the desert, while we've been running 5W-30 in
the g/f's Honda Civic since new (we live in a rather warm area of SoCal)
and neither vehicle has shown any ill effects. But they don't have the
345k miles my Subie does, so it waits to be seen what the long term
effects will be.

Mobil 1 is a very different kind of oil, and their 5W-30 might be better
under a load than a conventional 20W-50.

BTW - out of curiosity, is Ford now recommending their 5W-20 for use
in their trucks? I've seen Mobil 1 0W-20 on a store shelves - the
bottle says its an acceptable substitute for 5W-20.

 

[Rick Courtright]

Mobil 1 is a very different kind of oil, and their 5W-30 might be better
under a load than a conventional 20W-50.

Agreed on the fact it has some advantages over dino oil at the SAME
viscosity level. Not sure on whether you can compare widely different
viscosities between synthetic and dino oils, though.

BTW - out of curiosity, is Ford now recommending their 5W-20 for use
in their trucks? I've seen Mobil 1 0W-20 on a store shelves - the

I've heard that, too, but haven't asked anyone with a new Ford.

Personally, I think one's looking at shorter engine life in a truck (if
it's used as a truck!) with that light a grade, but I'm guessing the
engineers just might know more than I about the engine THEY designed!
(Sorry, I'm not as smart as all the barstool engineers who know SO MUCH
more than the guys who do it for a living...) Wonder if this might be a
precursive move toward manufacturers advocating synthetics in "regular"
cars/trucks (as opposed to Mobil 1 factory filled Vettes, Porsches,
etc,) here in the US?

Rick

 

[Rick Courtright]

I've heard that lighter multi-weight oils can get to places
heavier oils can't. Still - the engine is probably tolerant of
a wide range of oil weights.

I've heard that, and while it's true heavier oils don't flow as well as
lighter ones when cold, once the oil's up to operating temps, I doubt
this idea holds much water. Ever drain hot straight 40 wt or even 50 wt
oil from a car or motorcycle engine (back when these were recommended
grades?) The stuff's pretty thin compared to when it's cold and I don't
think it would have problems flowing thru a hot engine.

But, newer engines do have tighter tolerances, and in some cases,
smaller oil galleries, so I might be off base. I'm sure part of the
problem would be dependent on operating conditions: the guys in "cold
country" face a whole different set of problems than we "desert rats"
do! "Cold" to me is 40 deg F, while a guy in Buffalo, NY, right now is
probably praying for the temps to get that "high!"

Rick

 

[y_p_w]

y_p_w wrote:




Agreed on the fact it has some advantages over dino oil at the SAME
viscosity level. Not sure on whether you can compare widely different
viscosities between synthetic and dino oils, though.

I believe the original Mobil 1 was a 5W-20 weight, and they were
claiming that a thinner synthetic could protect better than the
typical 10W-40 that people were using at the time.

I've heard that, too, but haven't asked anyone with a new Ford.

Personally, I think one's looking at shorter engine life in a truck (if
it's used as a truck!) with that light a grade, but I'm guessing the
engineers just might know more than I about the engine THEY designed!
(Sorry, I'm not as smart as all the barstool engineers who know SO MUCH
more than the guys who do it for a living...) Wonder if this might be a
precursive move toward manufacturers advocating synthetics in "regular"
cars/trucks (as opposed to Mobil 1 factory filled Vettes, Porsches,
etc,) here in the US?

Honda went to 5W-20 in the late 90's, even though some of their
engines weren't redesigned. 0W-20 is the factory fill in their
hybrids. They also mandated a switch to their proprietary manual
transmission fluid (again - probably without a major redesign).
My guess is that motor oil has advanced far enough that 5W-20
can properly protect an engine.

As for Ford - I was just curious if they were recommending this
stuff across their entire offerings, i.e. - "You mean I'm
supposed to put 5W-20 in my F-350?"

 

[y_p_w]

y_p_w wrote:




I've heard that, and while it's true heavier oils don't flow as well as
lighter ones when cold, once the oil's up to operating temps, I doubt
this idea holds much water. Ever drain hot straight 40 wt or even 50 wt
oil from a car or motorcycle engine (back when these were recommended
grades?) The stuff's pretty thin compared to when it's cold and I don't
think it would have problems flowing thru a hot engine.

But, newer engines do have tighter tolerances, and in some cases,
smaller oil galleries, so I might be off base. I'm sure part of the
problem would be dependent on operating conditions: the guys in "cold
country" face a whole different set of problems than we "desert rats"
do! "Cold" to me is 40 deg F, while a guy in Buffalo, NY, right now is
probably praying for the temps to get that "high!"

The theories I've heard aren't just about mass flow of oil. I
heard some pseudo-scientific discussion about thinner multi-weight
oils being able to temporarily "shear" and re-expand - enough to
get into and lubricate modern rings better. I don't know - I
just use 5W-30 year-round in the San Francisco Bay Area.

 

[Carl 1 Lucky Texan]

I'd like to know what European (and Japanese, or Aussie for that matter)
owners' manuals have in them for oil recomendations - anyone monitoring
this group? preferably in engines or car models avaible here in the
states too - just to see if the viscosities are the same. I've read
20w-50 is quite often the weight of choice.

Carl
1 Lucky Texan

 

[y_p_w]

I'd like to know what European (and Japanese, or Aussie for that matter)
owners' manuals have in them for oil recomendations - anyone monitoring
this group? preferably in engines or car models avaible here in the
states too - just to see if the viscosities are the same. I've read
20w-50 is quite often the weight of choice.

From what I've gathered sometimes scanning their newsgroups, some
of the expensive German manufacturers (like BMW or Mercedes) have
recommended 20W-50 oil even for their US divisions. I recall when
Porsche switched to Mobil 1 as their factory fill, they said that
any weight available in the US (0W-30, 5W-30, 10W-30, 15W-50) was
acceptable, but that 5W-40 was used from the factory. The previous
BMW M5/Z8 engine was only supposed to use Castrol RS 10W-60. These
German cars now come with computers that calculate when a change
is recommended based on driving conditions, and reports are that
owners are getting at least 10K miles before they say to change.

The other thing we'd have to note is that the minimum API SL
and GF-3 standards are likely way lower than the ACEA standards
that are required in Europe. I also remember hearing how much
"regular" motor oil costs in Europe, and it occurred to me that
their standards likely required semi-synthetic or perhaps the
latest generation (I think it's called hydrocracked) motor oil.

Here's a page that describes the Mercedes system in the M-Class:

<http://www.4x4abc.com/ML320/ML_FSS.html>

BTW - Mobil is labelling Mobil 1 5W-40 as a "European Car
Formula", as it's what Mercedes and Porsches use out of the
factory.