Coming up with my own argument for 10w-30 in mine

[JHZR2]

Hi,

As most know, I have two MB diesels - an 81 and 82, one a 4cyl NA and the other a 5cyl turbocharged.

The older form of the oil viscosity/temp chart shows this:

Whereas the later version (manual states relevant to newer engine classes is as follows:

The newer one takes into account the CCMC G5, which is a precursor to the ACEA B set of specs, which is a solid diesel spec.

Im tempted to move into the rotella range of oils, running 5w-40 syn and T5 10w-30, but in the summer I can be in a situation where it is over 30C and Im running hard down the road. In the winter it is a rarity to be below zero.

So it seems that in spring, fall and winter, the 10w-30 oil would be usable... However in the deepest part of winter it IS nice to have a 5w oil versus a 10w oil.

SO while I think it would be neat to run the range, and perhaps even pick up a tiny bit of MPGs when on the 30wt, I cant see a good justification. Given the number of cars that I have, I could see maybe doing 5w-40 for the winters and summers and 10w-30 for the springs and falls... But Id need to be guaranteed at least 3000 miles of use per quarter and Im just not doing that right now given my travel schedule, commute, etc.

So Im thinking that 5w-40 is where I need to be, given one to two oil changes per year, to safely cover all bases.

Do you agree given the viscosity charts Ive shown? Given that a lot of my longer use is summer, when we definitely hit 90s on the roadways, 5w-40 is a necessity unless I change at minimum before the summer... at which point, unless Im driving 3-5k miles before changing, there is no good reason to change out to a 10w-30.

Thinking out loud but what would you do?

Thanks!

 

[HTSS_TR]

I agree, 5W40 is all you need all year according to the new chart. The small problem is 5W40 is syn oil and it costs more than 10W30 dino.

 

[Johnny]

I would use the 5W-40 year round in both the 81 and 82. Those are both extremely nice cars and the 5W-40 should serve you well.

 

[JHZR2]

Thanks!

5w-40 does serve me well. However, especially since the 82 is used for driving back and forth to DC, squeezing an extra MPG out would be nice... But my use profile just doesnt justify it I guess.

5w-40 it is.

 

[fdcg27]

It looks as though a current spec 10W-30 would be fine for your use.
From below 0F through the heat of the summer, there should be no worries.
Also, T5 is pretty cheap, and is no doubt a better oil than what was available when those 123s were new.

 

[JHZR2]

Id agree except that there is the real situation of driving hard and heavy traffic with temperatures solidly over 86F.

The cold start is less of an issue since going below 10 for an extended period is rare unless Im going someplace else... But it is that high temp situation that concerns me...

 

[fdcg27]

How much heat can one of those diesels put into the oil?
Neither the NA nor the turbo have very much specific output, nor do they rev very high. WRT the turbo, consider the oils used in them when they were new, and the very low rate of failure.
Also, both have ample sump capcity.
Can either one heat the oil enough that it would matter?

 

[JHZR2]

Doubtful... Turbo puts out about 12 psi full boost, cruising around 9psi. No intercooler, so the turbo is likely hot and then the ignition charge and subsequent temperatures are also hot I'd think. There are oil squirters on the pistons for cooling.

Dont have an idea of sump temp, though the sumps are roughly 11.5qt.

 

[Jim Allen]

As thin as possible, as thick as necessary.
Seems like you made the right choice with 5W40, though you could really fine tune it better if you knew oil temp. If you were short hopping, a 10W30 might be the better choice but extended running is where things even out a bit, as you know. Still, what if your oil temp is a lot lower than you think. The mileage loss is slight, but there if you are actually running a heavier oil than necessary. It's been too many years since I worked at a Mercedes shop for me to remember, but on some, from the '70s and early '80s, there era in which I worked on them, I recall a oil temp sensor, or at least a bung in the pan. Might have been the V8s.

 

[billpace1956]

Hello JHR2!! Why not the m1 0w-40? That's what the mobil1 website said to run in my mb's. I have a 1983 240d 4 speed manual with 242,555 miles on it. And I have a 1984 300sd with 200,567 miles on it. They start up super quick and the 300sd used about 1 pint per 5,000 miles and the 240d uses 1 quart every 3500 miles. I will get a uoa on the next oil change to see how far I can go on an oil change and what the soot level is. I went 5431 miles on my 300sd and 5351 on my 240d the last oil change. Thank You!