Which oil for the summer?

I have a Volvo 850GLT wagon. In the winter I used Mobil 1 5W30 synthetic.
Now I want to use Mobil 1 10W30 synthetic. The garage, do to cost wants to
stop using Mobil 1 and recommends German Lubro Moly Voll-Synthese 5W40.
Which oil should I use Mobil 1 10W30 or Lubro Moly 5W40?
I read somewhere on the net that to big of a range between low and high
viscosity rating is no good.
Adam

 

I use Mobile 1 5W30 synthetic year round, never had a problem with it.

 

I use that exact oil in my cars, and have since new, or when I first got
them. I don't think there's a lot of difference pricewise between it
and Mobil 1, I use the Lubro Moly because it easier for me to procure.

What you've read about wide range multigrade oils applies to some
conventional oils, because they need to use additives to achieve the
"multigradeness". These additives have large molecules that can break
down under stresses in the engine. These additives are not needed as
much in a synthetic oil, with is naturally multigrade to begin with. My
V70 T5 which I bought new in 1998 has seen nothing but Lubro Moly 5W40
since 8000 km, and had absolutely no varnish buildup with 8000 km
changes. It now has 135k km.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

The Lubro Moly 5W-40 synthetic is one of many very high quality oils
currently available and will be fine in your GLT.

John

 

Hello Adam,
I have a third option for you: Try the Castrol Magnatec GTX 5W40 fully synthetic.I
couldn't believe the difference when I switched from Shell Helix.Smoooth !

 

Is this the same Castrol that is marketed as synthetic, but is not
really?

http://www.lubes-n-filters.com/newsletters/syntheticsdefined.html

That's why I'll never buy another drop of Castrol oil.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Not synthetic, by the definition of synthetic used by just about every
other motor oil manufacturer. This particular oil does have polymerized
PAOs mixed with fractionated hydrogenated mineral oil and other additives.
The percent of PAOs is not disclosed (and may be altered with
notification to the customer). Some people call it semi-synthetic, which
to me is a meaningless term.

Beverly

 

But what I don't like is they call it a synthetic, they price it like a
synthetic, but it costs them way less to produce. If they tried to
market it as "Just as good as synthetic but cheaper" then maybe I'd
still be using Castrol. But I feel they tried to pull a fast one and
rip me off.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Also, I don't know if this is still the case, but their original
formulation that was pure fractionated hydrogenated mineral oil was
often associated with mucking up the oil pressure sending unit.

There was a thread about this in "Bob is the oil guy" forums several
years ago. My recollection is that most of the posts about this
problem were from Saab and Volkswagen owners.

Beverly

 

Finally I let the garage use Lubro-Moly 5W40.
From time to time I have to add some oil, is it ok to mix the above with
Mobil 1 0W40 which is easier to get?
I also don't like the Castrol claim and will not touch the staff.
Adam

 

Heh I'm sure the staff appreciates that