Date: Fri, 25 Jun 1999 13:18:34 -0400
Reply-To: Dominique Cormann <kozmik@WAVE.HOME.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dominique Cormann <kozmik@WAVE.HOME.COM>
Subject: Re: 5W30 Oil --- is it OK??? ( warning long response )
In-Reply-To: <5b3c6b2c.24a4d7ed@aol.com>
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On Fri, 25 Jun 1999 09:02:37 EDT
Todd Thompson <ThZouave@AOL.COM> wrote:
> I think that it can be important to note what the numbers of oil mean. 5-30
> or 15-50. The first number is the weight of the oil when cold. the second
> number is the weight of the oil when HOT. Most oild get up to operating
> tempetures very quickly. It is important to have the same high temperture
> number as recomended. the lower number helps provide lubrication at start up.
> Especially in cold weather. There are some questions about wide ranging oil
> such as 5-50; they use additives to make a "thin" oil to stand up in heat
> (instead of thining out even more). These additives will wear out faster than
> your oil. Try and stay away from oils that have a "shift" that are more than
> 15-20 points.
>
In general you are correct, but not all oils use additives to achieve
this. The Mobil your using, for example uses no additives to achieve
things like the 5w50 they have. But the others do w/ Amsoil being
another non-additive exception.
> If you are a real oil nut use cheap oil and change it every 1500 miles or so.
> synthetic is great but still builds with crud like any other oil. ( I use
> mobile 1 syn. 15-50 and change every 3000)
>
Thats what I used in my gas cars. A good synthetic, and changed at
normal oil intervals.
However, I have a new theory, now that I've been spending time around
diesels.
This last weekend, I helped my friend rebuild a 87 TD engine, for
placement in his Vanagon. We were really impressed how clean this over
300,000 kms engine was inside. The previous owner used diesel rated oils
(15w40 cg-4) and changed at the manuals stated times. Normal wear had
occured. The rings were almost totally worn, to the point of
contact...hadn't yet allowed the pistons to make contact, but would have
soon. No blowby. The main bearings showed no wear, the rod bearings also
showed little wear. In the pan and around the engine we saw NO SLUDGE at
all. In fact this isn't the first time I've seen this. Completely
sludgeless engines when taking apart diesels where the owner made sure
to use diesel rated oils. Diesels produce more sludge then gas engines,
so the oil has a tougher job. Soot, and other deposits create 10 times
the sludge, but a good diesel oil has detergents for the deposits, and
other additives that break apart soot.
While talking with places that rebuilt truck diesel and gas motors,
they recommended using the diesel oils in the gas engines for the reason
that they contain better detergents and when they rebuild the gas
motors, they see evidence that it makes a difference.
This is why some oil companies don't call there diesel oil, just diesel
oil, they called them mixed fleet oil. Since they carry both the Cx ratings
and the Sx ratings.
After taking apart some engines, I feel more confident about
Diesel/mixed fleet oils, compared to oils that just meet Sx ratings.
Also to be honest, I'm feeling less confident that using synthetic makes
a difference.
When seeing different engines apart, I noticed little difference if they
had used synthetic or mineral. (keep in mind the climate, if I was
further north, I'd say use synthetic period). So if I see little
difference in wear, then the difference in cost factors in. The cost
savings of using a premium mineral based oil would add up large enough
to pay for the rebuild ( I do the work myself - so I'm talking parts ).
We paid $320 in parts (canadian money) to get everything we needed to do
the rebuild on the TD motor. We did a full rebuild, not just re-ringing
the motor obviously.
I can buy a pail of diesel 15w40 CG-4 oil for around $29 canadian.
Synthetic stuff is $70-$180 for the same 20L pail. Mobil 1 delvac being
the high end of that price range.
The reason I think I'm seeing no difference is that the synthetic oils
used were for gas engines, and even the one I saw that used Mobil 1 all
its life, had sludge buildup...that particular engine actually died of
oil starvation. The engine was a gas engine, so it was using the right
oil, and changed at every 3000 miles ( us person ). However ppl I know
that have used Diesel mineral based oils ( whether in gas or diesel
engines ) have seen about the same level of wear. No sludge build up.
The engine I saw that used mobil 1 would have lasted a long time, if it
wasn't for the oil starvation. The wear occured rapidly, after the
sludge had plugged up most of the oil galleys, and starved parts of the
engine.
So now I'm less confident in using synthetics in normal climates. Unless
we are talking about using a diesel synthetic oil, but then you have to
factor in the extra cost of it.
--
============================================================---------
Dominique Cormann Email:kozmik@wave.home.com
dcormann@uoguelph.ca Homepage: http://kozmik.guelph.on.ca
