10w-40 vs. 15w-40

[The Critic]

Originally Posted By: fdcg27
I dunno, maybe?
Another possibility is that the thicker oil brought lower consumption, which in turn allowed more timing advance, and thus lower fuel consumption.
A third possibility is that Mobil 1 15W-50 contains a significant ester component (Mobil isn't telling) which would provide reduced friction.
Also, esters may (I wrote may) degrade fuel octane less, thereby allowing more timing advance.
Anyway, the old thing did very well on Mobil 1 15W-50, while fuel consumption was no lower in the first 4K run of Maxlife 10W-40, and the oil leaks, absent with the Mobil 1 15W-50, have returned.


Can't I use 20-50 in my climate? It rarely falls below 45 here.

 

[fdcg27]

You sure could.
BMW recommended it when the car was new for the temperature range you'll see.
Do you want to, though?
If you don't mind spending a bit more, I'd recommend Mobil 1 15W-50 based upon my experience with it.
The only reason I'm not using it now was that I used the last seven quarts I had over the summer, and I'm trying to use the oils I have stashed.
I also thought that Maxlife 10W-40 would be a good choice for it.
So far, I'm not so sure, but I'm on my second run of this oil and have two more left to go, so we'll see if my opinion of Maxlife 10W-40 changes.
While I've never tried 20W-50 in my BMW, I did use GTX 20W-50 in our last old Mercedes during warm weather, and the engine seemed fine with it. Neither fuel economy nor engine responsiveness seemed to suffer noticeably.

 

[Garak]

Originally Posted By: The Critic
Is there any good reason why I should choose a 15w40 over a 10w-40? So far I haven't.


Cost might be one. Up here, a 15w40 in a pail is substantially cheaper than 10w-40 in quarts (which is how they're usually found here). It only gets worse with high mileage oils. Don't get me wrong; I think MaxLife is a great High Mileage oil and I've used it when I needed something lighter for winter. For your climate, I'd use Delvac or Rotella 15w40 and be done with it. Both have stout add packs and a great price.

 

[fpracha]

Originally Posted By: Garak
Originally Posted By: The Critic
Is there any good reason why I should choose a 15w40 over a 10w-40? So far I haven't.


Cost might be one. Up here, a 15w40 in a pail is substantially cheaper than 10w-40 in quarts (which is how they're usually found here). It only gets worse with high mileage oils. Don't get me wrong; I think MaxLife is a great High Mileage oil and I've used it when I needed something lighter for winter. For your climate, I'd use Delvac or Rotella 15w40 and be done with it. Both have stout add packs and a great price.

Well do you feel that 15w40 vs 10W-40 oils is not much of a practical differences discussion here?

 

[45ACP]

Originally Posted By: The Critic
Originally Posted By: fdcg27
I dunno, maybe?
Another possibility is that the thicker oil brought lower consumption, which in turn allowed more timing advance, and thus lower fuel consumption.
A third possibility is that Mobil 1 15W-50 contains a significant ester component (Mobil isn't telling) which would provide reduced friction.
Also, esters may (I wrote may) degrade fuel octane less, thereby allowing more timing advance.
Anyway, the old thing did very well on Mobil 1 15W-50, while fuel consumption was no lower in the first 4K run of Maxlife 10W-40, and the oil leaks, absent with the Mobil 1 15W-50, have returned.


Can't I use 20-50 in my climate? It rarely falls below 45 here.


You can.

Supertech API SN 20W-50 conventional IS manufactured. As well as Pennzoil conventional API SN 20W-50 conventional, if you prefer.

You will get

for using an old heavy oil grade, but if i works for you.. use it.

 

[45ACP]

Originally Posted By: BikeWise1
I, too, drive an older BMW, a 1985 535i with the M30 engine. This engine has 280,000 miles on it! I have used Mobil 1 15W-50 in it, however it gets cold here in Ohio. Based on some very good used oil analysis, I have been continuing to use Mobil 1 High Mileage 10w40. No leaks and low consumption. Great anti-wear package in this oil.

There are those who run Valvoline VR-1 Racing 20W-50 in these engines because they have, in my opinion, an unreasonable fear of cam wear and believe the added ZDDP will help. I am old enough to remember that BMW 2002 owners were similarly wringing their hands over valve seat recession when lead was being removed from gasoline. However, BMW's metallurgy is top notch and the problem never manifested itself, just as it won't now with cams. An acquaintance who has been an independent BMW mechanic for 25 years states he has *never* seen a worn cam in an a properly oiled engine. Meaning the oil pressure was good, and the sprayer bars were functioning properly.

I think the fact there are so many of these '80's BMWs still driving around means the actual oil in the car isn't as important as making sure the oil is not worn out, and that the systems that deliver the oil are functioning.


40-weight or better in an 80s Bayerische Motoren Werke. The oil pressure needs to be a touch higher, these engines like it. GC AT THE MINIMUM!!! 15W-50 could get tested in Ohio, the Mobil 1 10W-40 was fine there. (coulda maybe stuck with 15W-50 unless it got more than -5 below.)

I should know, I had the M20B27. Same foes for the M20B25 and Super ETAs.

I would never own a first-gen 5-series due to that retarded exhaust pipe in the middle. Same with an M6, unless i got that changed for the M6 1st gen.

 

[Garak]

Originally Posted By: fpracha
Well do you feel that 15w40 vs 10W-40 oils is not much of a practical differences discussion here?


Personally, no. Neither are particularly good cold weather oils, so I wouldn't be one to obsess over the 10w-40 being lighter in the cold than 15w40. When my old truck was leaking and making other miscellaneous noises before the rebuild, I used the MaxLife 5w30 in the winter, and just went to a cheaper 40 weight in the summer. I stuck with 15w40 simply due to better availability and cost.

If I needed a 40 weight without any strange specifications beyond say SM, I'd just stick with the dual rated 15w40.

 

[4x4chevydude]

I would do the 15w40 personally becuase its ease of finding it at walmarts and whatnot.

 

[Garak]

Originally Posted By: 4x4chevydude
I would do the 15w40 personally becuase its ease of finding it at walmarts and whatnot.


Exactly. I can't speak about the U.S., but I do know that up here, it's rather hard to find 10w-40 in the big jugs, or to find much variety in brands of 10w-40. When it comes to 15w40, it's easy to find big jugs, and then some.

 

[Norm Olt]

In CA just about any 15w40 HDEO is more than overkill for your BMW. BTW, 5K w/b, IMHO, a more reasonable OCI.

Could probably go with two oil changes per filter change, as well...

Especially if BMW used a cartridge-type filter.

Cheers!