OK, I've been trying to stay out of another (repeating) oil thread, but here
goes:
The most wear that an engine experiences is during a cold start. Oil
pressure isn't up, oil has drained down into the sump, and clearances are at
their greatest. So it makes sense to use an oil (such as a good synthetic)
that "clings" best to metal surfaces, and that will quickly flow through the
passages when the pump starts.
Heavy duty engines use pre-heating and pre-pressurization of the oil system
before they start. Most car engines don't have that luxury, hence the need
for some common sense like using a good oil, not loading the engine until it
gets a bit of heat into it (Note: that does not mean idling for 5-10
minutes!). And gasoline fuel engines do not put as much loading on rod
bearings as Diesels do, so a very "thin" oil works out OK.
Also, the thinner the oil, the less work it takes to pump it through the
engine, hence the claim for better mileage with 0W-40 rather than 10W-40 is
theoretically true. And the car manufacturers have a vested interest in
getting the highest CAFE ratings, and don't want the car to last forever, so
they recommend the thinnest oil that will get them through the warranty
period, and perhaps another year or two. But please remember that the
manufacturer has a recommended oil viscosity for each engine, and I'm not
aware that 0W- anything was ever recommended for 70s, 80s, and early 90s
vintage M-B Diesels in our climates!
That said, for a Diesel that you may want to last for 200, 300, or 400
thousand miles, it makes sense to use a "C" rated oil, such as the 15W-40
Delvac1. Remember, oil is less expensive than metal - meaning that an
engine rebuild always costs more than you could possibly save by skimping on
oil or using the wrong viscosity.
Werner (sorry to keep this going)
'90 300D
'83 300SD
'87 F150
----- Original Message -----
From: "Zoltan Finks" <[EMAIL PROTECTED]>
To: "Mercedes Discussion List" <mercedes@okiebenz.com>
Sent: Friday, December 29, 2006 1:59 PM
Subject: [MBZ] Trying out 0Wxx Mobil 1
Not that I haven't taken heed of all the posts on this, but to my brain at
least, the following excerpts (below) seem to make sense to me, and here's
why:
If there were no difference (negative) in using 0W Mobil 1, why doesn't
everyone run it, and thus receive the (claimed on the bottle) benefits of
better fuel mileage, and better cold starting (if that's an issue where
they
live) than the other weights of Mobil 1? In other words, most people would
be running 0W if there were no side effects.
Brian
83 240D
84 Saab 900 (received the 0W30 Mobil 1 last night)
Curt wrote:
I'd put 0w40 into my 240D and it leaked like crazy. Maybe a quart in 100
miles.
I tried 5w40 (this was a couple years ago when the 5w40 was easy to find)
and it leaked maybe a quart in 300 miles.
15w50 leaked a quart in maybe 350 miles, same with conventional 15w40.
(snip)
and:
What have you been running in it up to now? You're mostly right about how
the oil works but it is very thin and you shouldn't be surprised about it
leaking more. (snip)
