You can also use Shell Rotella T Synthetic 5w40... they are available at
Wal-Mart for $3.99 a quart... sold in gallon container. I just picked up two
bottles. In October, they will have newer oil that meets CJ-4 rating for
Right now, they are CI-4Plus... which is the highest availble now. I am
currently using Mobil 1 Truck & SUV 5w40... which is the ONLY Mobil 1 oil
designed for Diesel engine. You can get Delvac Synthetic but are hard to
find and super expensive. As far as I know... Delvac Synthetic and SUV oil
is the same.
At this time, Shell RotellaT Synthetic is the best deal.
I have been a Mobil 1 user for just under 30 years and recently
switched to Amsoil after doing some research. Mobil 1 was at one time,
I believe, a true 100% synthetic oil, but has reformulated their
product by doing something called "hydro-cracking." It leaves you with
a good product for lubrication, but it does not maintain the same
quality over the long haul as a true synthetic.
Amsoil is one of only two 100% synthetic oils on the market and the
company makes no bones about sharing its test results with you. Mobil,
on the other hand, uses all sorts of marketing terminology that are at
best, technically non-specific, and at worst, misleading.
The only thing I don't like about Amsoil is their marketing approach.
You can rarely find Amsoil at a retail outlet and must usually purchase
through one of their representatives. To be fair, I believe this is due
to the fact that most retailers don't want to sell an oil that is
capable of oil change intervals far in excess of conventional motor
oils. The retailer cannot sell nearly as much oil if their customers
are using Amsoil.
I don't want to waste your time going on about the value of TRUE 100%
synthetic motor oil, but I recommend it highly. If you have any further
questions, I would be happy to answer them. However, I have found the
Amsoil website to be one of the best manners of education available.
If you want to learn more even outside of the Amsoil site, there is
another great site about synthetic oils by a company called Synlube. It
is extraordinarily expensive product, but I have found its claims to be
true. It is not practical for diesels as the soot factor mandates one
change the oil long before its lubrication qualities are exhausted.
Hope this helps.
Thanks for the detailed info. I had used Amsoil in my Mazda RX-7 years back
and amazingly it got about 10% better mileage. I still find it hard to
believe Amsoil can reduce friction by such a significant amount, but it did.
Have you noticed this in your MB diesel also?
Do you feel it is safe to extend the drain interval to 15,000 miles, or once
a year, as recommended? Do you use a 3 micron bypass oil filter to keep the
oil clean? I hear truckers change oil once in 25K miles, with oil analysis.
I do plan to switch to Amsoil from Mobil 1 from my next change.
I live in Florida. What weight do you recommend, 5W40 or 15W40, for my 1999
Do you purchase Amsoil by mailorder or thro' a dealer?
The selling point of synthetic oils is that they're more resistant to
breakdown from high temperatures than dino oils are. However, the
reason diesels generally have shorter oil-change intervals than gaso-
line engines isn't thermal breakdown; it's because the oil gets dirty
a lot faster.
I run Mobil 1 or Castrol Syntec in my 300D 2.5, but I change it every
4,000 miles just like I would dino oil.
"Like swallows heading for Capistrano, liberals are drawn toward
those institutions where they have the power to impose their
That is a waste of oil... but the oil you use is not designed for Diesel
engine... take a look... there is no CI4 rating or anything about diesel.
Stick to Mobil 1 Truck & SUV 5w40 or Shell RotellaT Synthetic 5w40 (much
cheaper). Or go Amsoil.
On newer diesel, change interval is 7500 miles or so...
Well, what oil change interval would you recommend for a '91 300D
2.5 with 107,000 miles on it, then?
Anecdotally, five thousand miles between oil changes seems to be
a common interval with gasoline engines (and easy to keep track
of, to boot), so I figure knocking a thousand miless off of that
in the case of a diesel is rational.
(Wasn't a *three*-thousand-mile oil change interval recommended for
the W115 240D and 300D back in the '70s? I seem to remember reading
that in one of the car mags way back when...or "back in the day," as
the kids like to say.)
I'll look for 'em -- thanks -- but it's damned near impossible to
find my preferred grade of Mobil 1 (15W-50? something like that)
as it is. I don't think I'v ever seen "diesel rated" motor oil of
any brand for sale in my entire driving life. Maybe it's in the
"A liberal is someone who feels a great debt to his
fellow man, which debt he proposes to pay off with
Look in your manual... it would say for regular oil at 7500 miles... but
that is not recommended by diesel purists. With synthetic, I would go 7500
miles. If you do not want to use synthetic, then 3000 miles is what I would
The old days with regular oil... 3000 miles is recommended. Modern engine
now burns so much cleaner so oil change interval is much higher.
Diesel rated synthetics starts with 5W... regular diesel oil starts with
15W. Walmart has Shell RotellaT Synthetic Oil in dark blue gallon
container... $3.99 a quart price... so you are paying $15.96 per gallon.
Diesel rated oil has better property to keep the soot in suspension and
control while regular oil or non-diesel synthetic do not have those
properties. Diesel engine also have much lower RPM and temperature operating
condition so diesel oil is not recommended for high performance gas engine.
The highest rated diesel oil is now CI4 Plus... CJ is coming in winter. If
you look at regular oil, you will see like CH or CF rating instead. CI4 is
designed for diesel car with EGR system... or otherwise the EGR will clog
Gas engine now for MB now has 10000 miles interval with Synthetic oil. Older
MB had 7500 miles with regular oil... and the two decades ago would ask 5000
miles... The main thing is engine has changed so much that it ran so much
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