15w-50 oil for the Boxer (Motorex and BMW VOAs)

In case anybody is curious

BMW branded 15w-50 (the current Made in Italy red stuff)


Motorex Boxer 4T 15w-50


These were fresh oils straight from the bottle. Not sure what that iron, silver, and silicon are doing in the BMW oil.

Silicon is used as an additive. It is also a contaminant. Too much is no good but that is well within the acceptable range for a synthetic engine oil.

On the Ams Oil same weight but this was run for almost 10K miles in the GS.
Interesting comparisons.

Low TBN. Not in my boxer engine.

This oil would likely be fine for seversl thousand more miles.

You can't really tell anything from virgin oil TBN since they don't all degrade at the same rate. With a 6200 mile change interval, I am sure the TBN numbers are enough. In fact, there are reasons to favor a low TBN when possible anyway (see http://papers.sae.org/2007-01-3999/)

I have to be honest; all these numbers (when it comes to oil) mean very little to me, without someone else deciphering the data for me I can't make heads or tails of any of it.
I'm a simple person, the manufacturer tells me the specification of the oil that my machine requires and I go out and buy it, not often do I purchase my oil from the dealership as their prices are usually too far out of whack.
I believe that a lot of the attributes regarding oil quality mean almost nothing if you change your oil at the recommended intervals.
That is not to say that I don't find oil threads fascinating and try to learn something from them

Well, I think the take away here is that while Motorex's fancy bottled Boxer 4T was developed with AC Schnitzer, it looks like it is a worse oil albeit a slightly more pure oil.

I have to wonder how these numbers compare to Mobil-1 15W50 which is probably the most used boxer oil, so I found this almost 4 year old oil report on virgin Mobil-1.
Can someone help me understand how this compares?

This Mobil1 15w-50 VOA is typical of a high quality synthetic engine oil rated SN. The previous Amsoil UOA shows almost equal quality after 9900 miles in the boxer engine. I would say the Amsoil is better oil for the boxer than the Mob1. However, we're comparing oranges to onions here, used oil vs. new oil.

I still like Mobil1 15w-50 because it is available at relatively low cost. There are better oils however.

Jet, you are right...use the correct rated/vis oil in your boxer, change at the recommended intervals and it is unlikely you'll ever have an engine related failure.

You're clear for takeoff.

I would say that Mobil 1 that was analyzed is pretty good - low detergent, which is fine for the change interval called for, good amount of anti-wear additives.

I use Mob1 15w-50 and change annually regardless of miles. The used Mob1 is then used a bar oil for the chainsaw.

Amen to that one, brother. Mobil 1: readily available; relatively inexpensive; and real good. I've run it exclusively in bimmers and beemers for decades with nary an issue.

As noted, the "used" oil can be recylced into less expensive machinery. My lawn mowers have only ever been filled with oil taken out of BMW products. Well, at least since I could afford BMW products.

Ok... I am probably going to catch hell for this one.. I have a lot of time to sit and wonder.. And this seems like the group to ask...
If I had equal parts 10w-40. And 20w-50, and mixed them together would that be 15w-45 .... Or am I way off base... Not sure how any of that works....

Thanks in advance ...

Damn, I wish I had your free time! :huh

I'm no oil expert but from what I understand your logic is somewhat accurate except that it most likely have an end result of exactly 15W45, the only thing that's for certain is it will be somewhere in between and probably just fine to run in your engine.............not mine, I'm too anal.


Even though you didn't ask about this next part, I will add it just for fun:
The issue you may run into is mixing different brands and types of oils with different additive package, rumor has it that some additives could neutralize or otherwise damage others.

IMHO, I would not suggest mixing different oils (and using in an expensive engine) just because you have them on the shelf, save those for the lawn mower or your mother-in-laws Ford Escort wagon.
But if you're in a remote place and all you have is several small amounts of various oils then by all means, some oil is better then no oil, I have heard several occasions of people needing to this and have yet to hear of a catastrophe from doing so.

Not a rumor, additive clash is a real thing, the question is just degree.

I'll have to take your word on it, and while I don't disagree that some additives may have adverse reactions to others, I have not seen any evidence that supports this and have not heard of one motor being damaged by it.

Like I said, it's an issue of degree. The only people I've ever known to be concerned with it were Nextel Cup engine builders when going from break-in oil to running oil.

Just to clarify, M1 15w-50 would not be good to use in Wethead boxers but it's hard to beat for prior models. Especially when cost and availability are factored.