Something does not pass the 'Common Sense and Good Judgment' check. What am I missing

[Shipkiller]

Due to the types of driving I do and the amount of track time, I am contemplating changing out my differential oil now at 27K, before my next track weekend at the end of the month.

I don't have any issues performing this maintenance but a question came into my head. Why do I have to do this fluid change on the ///M when, on my pickup truck, which pulls/hauls HEAVY things frequently, is performed at an even greater interval? I only have to change the rear differential fluid at 60K and the front differential fluid at 20-30K (due to water intrusion going off road).

I am still under warrantee so I am going to use the very rare and had to find liquid gold, Castrol SAF-XJ.

[tekmoe]

Per BMW, you should change the diff and tranny oils at every Inspection 2 service. I changed mine shortly after Inspection 1. It's simple but at the same time makes me feel good knowing I have fresh fluid in the most important components of the drivetrain.

[Finnegan]

It's a good question, and one I'm thinking through as well for both the diff and the transmission.

Here is a link Pal posted showing Blackstone results for diff changes at 18K and another 20K. Draw your own conclusions, but it looks like things are just fine and probably no reason to change at other than the recommended intervals (although it sure looks nasty). Pal puts a lot of track wear on the car, so the argument for more frequent changes for a car that doesn't see the track is a peace of mind thing IMO.

As for the transmission, I have yet to find those results, but I'll keep looking. But IIRC you've changed that out more frequently, and at least using one brand it looked like even at 14K miles it was toast, correct?

[wassup61]

Originally Posted by Shipkiller

Due to the types of driving I do and the amount of track time, I am contemplating changing out my differential oil now at 27K, before my next track weekend at the end of the month.

I don't have any issues performing this maintenance but a question came into my head. Why do I have to do this fluid change on the ///M when, on my pickup truck, which pulls/hauls HEAVY things frequently, is performed at an even greater interval? I only have to change the rear differential fluid at 60K and the front differential fluid at 20-30K (due to water intrusion going off road).

I am still under warrantee so I am going to use the very rare and had to find liquid gold, Castrol SAF-XJ.

Clutch type differential in M vs mechanical in truck. The clutch type disperses the wasted material into the oil. Clean oil=longer life of the differential clutch packs. If you track it, once a year is a good policy.

Remember that 1 track mile=10 street miles.

[Finnegan]

Originally Posted by wassup61

Clutch type differential in M vs mechanical in truck. The clutch type disperses the wasted material into the oil. Clean oil=longer life of the differential clutch packs. If you track it, once a year is a good policy.

Remember that 1 track mile=10 street miles.

Totally agree with the 1 = 10 and it's a point well taken.

On the other hand, the Blackstone analysis on the diff fluid that Pal had done seems to show no issues even with 20K miles (a lot of those being track days) unless I'm missing something. Fluid seems fine, and that would seem to support a longer interval even with track use. (2 analysis completed, see my post and links above.)

Hadn't thought of the mechanical vs. clutch angle though...good point there.

[wassup61]

Finnegan,
The clutch particles in the fluid causes progressive degenerative wear in the clutch packs. The oil may not shear down and the additives may be AOK, but the clutches will wear faster.

Oh... and I like your choice of cars, I have a z4 3.0si coupe, and 2011 golf tdi (base car) as daily

[BTM]

Fluid changes are preventative maintenance & cheap insurance - if analysis shows no degradation that's a good thing. The point is to change it before it degrades or something else starts going wrong, to prevent such situations.

[Finnegan]

Originally Posted by wassup61

Finnegan,
The clutch particles in the fluid causes progressive degenerative wear in the clutch packs. The oil may not shear down and the additives may be AOK, but the clutches will wear faster.

Oh... and I like your choice of cars, I have a z4 3.0si coupe, and 2011 golf tdi (base car) as daily

Got it, good point. RE: the cars, thanks, the TDI is a great DD! A bit bizarro world (low revving, FWD, etc.) compared to the Z4 though ain't it?

Originally Posted by BTM

Fluid changes are preventative maintenance & cheap insurance - if analysis shows no degradation that's a good thing. The point is to change it before it degrades or something else starts going wrong, to prevent such situations.

Point taken.

Good discussion guys, thanks! I'm moving forward with my higher frequency diff/transmission fluid swap program (~25k), which is about half of the recommended interval. With the track miles we put on the cars there's a good argument for it. Guess we'll need to see what Ship thinks--but looks like he should have some input to work from.

[Shipkiller]

Just arrived back from the dealership where if I provide (I did) my own bottle, the standard SAF-XJ is $14.50 a liter. Two liters plus two new plugs had the total cost of $45.00.

The SAF-XJ w/FM Booster is $45.00/liter... That 'friction modifier' must be made of gold particles...

[tekmoe]

I went with Redline 75w140 for the diff and Royal Purple Synchromax for the tranny. No complaints whatsoever.

[Shipkiller]

My independent mechanic told me that you can use any other brand of fluid in a ///M for all the other fluids, but DO NOT use anything else except SAF-XJ in the differentials....

[tekmoe]

Been running the 75w140 in the diff for the last 10k miles, not a single issue. No weird noises, feels just as it did with the OEM fluid (which was probably never changed since the car only had 28k miles on it when I bought it). I have heard and read to stick with Castrol TWS 10w60 for the engine though which I will continue to use.

[inTgr8r]

Originally Posted by Shipkiller

Just arrived back from the dealership where if I provide (I did) my own bottle, the standard SAF-XJ is $14.50 a liter. Two liters plus two new plugs had the total cost of $45.00.

The SAF-XJ w/FM Booster is $45.00/liter... That 'friction modifier' must be made of gold particles...

^wish we could do that up here.

[jmillet]

My track driven Z4MC is out of factory warranty so I recently put a 50/50 mix of Red Line MTL and MT-90 in the transmission and 85W-145 in the differential.
I ran Red Line fluids in my former Z3 M Coupe for over 70K miles with many track miles and never had a problem. I change these fluids out annually.

[wassup61]

Non oem fluid will cause diff wear at an accelerated rate. Those clutch packs I was talking about are designed with a material that disperses well in saf xj. The additive package is specifically formulated to work with the chemistry off the clutches as they grip. I find it funny when people go non oem and say they feel a power increase and greater wheel spin... Their clutches in the differential are slipping more and wearing faster

[mfanatic325]

Originally Posted by Shipkiller

My independent mechanic told me that you can use any other brand of fluid in a ///M for all the other fluids, but DO NOT use anything else except SAF-XJ in the differentials....

My indy shop also mentioned this when I got my diff rebuilt for the 3.91 ring & pinion install. All of the employees there used to (or currently still do) auto-x and track their BMWs, and they've found through years of experience that OE fluid for the diff is the best way to go; and perhaps cheaper in the long run.

I don't see any reason not to try aftermarket fluids for stuff such as transmission and clutch/brake fluid though
But I'd personally stick with the factory-recommended motor oil and diff fluid just in case

[tekmoe]

Yep you keep on buying that OEM fluid...

[BTM]

Originally Posted by tekmoe

Yep you keep on buying that OEM fluid...

Why so anti-OEM fluid? Cost?

As wassup61 said, BMW and Castrol have a partnership in lubricants. Just like TWS 10W60 was developed in conjunction with the M division, BMW specs SAF-XJ and SAF-XO for differentials for reasons beyond viscosity. Shear stability, operating temperature, interaction with seals, etc are all elements beyond the simple question of "will this lubricant work." Claims of increased efficiency and less wear are offered without support. A common mentality is "if it's good enough for X race car, it's good enough for my street car" which completely fails to take into account the rebuild cycles race cars see. Driveline components are being rebuilt exponentially more often on race cars than they are on street cars, and in these cases longevity may very well be traded for sponsorship money (this is not to say the fluids are inferior in a race application, however) since the parts will see a rebuild anyway

As far as the higher price for OEM, there may be some price fixing at play, as Castrol being the OEM fluid and therefore the most preferred, but for my own car, there really is no reason not to spend a few extra dollars and go with the recommended stuff. In the end, do what you will with your own car, and it's likely we are examining the minutia of the situation. However, I was well aware of maintenance costs when I bought the car, and for me, it's really a case of there being no good reason NOT to run the SAF-XJ

[tekmoe]

BTM, you do raise valid points and some of them I do agree with. However, based on my own experience for the last 10 or so years using various aftermarket synthetic oils, you really can't go wrong with any of them. I prefer Redline over the rest but that's only because I've been using it the longest and have never ever ever ever ever had any engine/transmission/differential problems after thousands upon thousands of miles driven on the streets, both cars and motorcycles. That and it's cheaper than OEM fluids. I've also ran Royal Purple (currently in my transmission), Amsoil, and Mobil1. They are all good. But for the guy who has never used any aftermarket oils, I could see why he would be more prone to sticking with what good 'ol BMW recommends.

[Shipkiller]

I have run Amsoil in my other vehicles for the last 17 years or so. I like it a lot. It does cost more than some of the the other dino, semi-synthetics, ester based and PAO based lubricants. I even run it (Amsoil) in the Roadster, from the engine to auto-transmission to differential.

Since non-FM SAF-XJ was only $14.00 from the dealer, is is almost a no brainer to still use it since my car is still under the factory warranty.
If I could find a better engine oil than Castrol 10W60 I would use it but trolling through literally hundreds of threads on various forums no one can come up with any verifiable numbers that anything is better than Castrol 10W60 for the ///M cars. You also have to take into account that 90% of all drivers on the forums don't really stress their drive line components by taking their cars to the track.

I originally asked the question since two of the diesel inspectors (Navy diesels) at work ask me the question. I completely forgot about the clutch packs in the differential that my pickup and most others do not have.

This thread has inadvertently come up with some good points without it degrading into a flame war or yelling match.

jmillet, I am interested in how your transmission feels after about 10K with that mixture. I am still running RP Syncromax but I did change it after 12K. I found that my shifting started to degrade so anything better is a plus.

BTM, you are spot on about race cars. Especially when talk in the office turns to motor oil and NASCAR.. I usually stay out of the debates but sometimes I show a article from one of the NASCAR rags (I dislike NASCAR) about the motor oil they use, when someone states that they use the same oil as in the NASCAR race cars. Here is the piece I found about two or three years ago:

The most advanced piece of technology in a Nascar vehicle these days isn't its engine, its suspension or anything made of carbon fiber. It's the motor oil.

Joe Gibbs Racing, a team that owns three top-level Sprint Cup cars, has spent about $1 million a year over the past decade to perfect its motor oil. As a result, its engines have squeezed out an extra 10 horsepower, a roughly 2% increase that can be a serious advantage in Nascar races, where the typical margin of victory is about one second.

With Nascar increasingly cracking down on the use of technology in the sport to cut costs, motor oil is one of the last places teams can innovate without restraint. Companies like Shell, Quaker State and Mobil also make special oils packed with synthetic lubricants, new polymers and experimental molecules for the teams they sponsor.

All this has spawned a culture of secrecy. Shell was so worried about protecting its motor-oil formula that it recently refused to allow used race oil to be sold as a souvenir to Nascar fans. The concern, a spokesman said, is that someone could "reverse engineer" the used oil to see what its properties are. Joe Gibbs Racing, one of Nascar's richest and most-successful teams, won't say which company assembles its synthetic oil and will only identify the scientists who work on its formula as "William the chemist," who's in charge of formulating the oil, and "Douglas," who used to work for NASA and is in charge of analyzing the team's worn engine parts under a microscope. "I don't want other teams trying to find out who these guys are," says Lake Speed Jr., who runs the team's oil program.

A couple of times a year, Mr. Speed gets a new shipment of experimental oil in nondescript black pails marked with code numbers. Mr. Speed tests it for 500 to 600 miles in actual Nascar racing engines powered by $2 million computerized simulators called dynamometers. Mr. Speed sends the used oil back to William and Douglas at the lab in clear plastic vials, along with some of the worn engine parts. Then the process starts over again until a new, improved formula is found.

There's no big commercial market for these oils. If they were used in a normal passenger car, experts say, their unfamiliar additives would destroy the catalytic converter. They also contain more sulfur, which makes them reek of rotten eggs.

Gibbs Racing says it makes up for some of its research costs by selling its own branded oil to amateur auto racers. The team's officials admit it's not the same oil the team's drivers use: Their formula is a secret combination of its retail brands. "I'm not going to give you the whole recipe," says Mr. Speed.

The two main purposes of motor oil are to make the engine run faster by lubricating all of its moving parts and to create a liquid film between metal parts that keeps them from rubbing against one another. The challenge in auto racing is creating oils that are strong enough to protect the engine while being slippery enough to allow the engine to reach higher speeds.

Motor oil has become increasingly important in Nascar, which tightly controls the technology in its cars and tries to keep costs down to lure more sponsors and more teams. Unlike the enormously complex and high-revving engines in Formula One, Nascar engines -- with eight cylinders, carburetors and push rods -- are not unlike those installed in a 1967 Chevy Camaro. Motor oil is one of the few areas where rich teams can use their money to get an advantage.

Most Nascar teams have one motor oil for long, 500-mile races and another for the single qualifying lap on Friday that determines their position on Sunday. (All this oil changing means each car will use 1,000 gallons of motor oil per season).

Qualifying oils are thinner and faster, while regular motor oils have more viscosity to protect engines longer. Before Talladega last season, Joe Gibbs Racing decided to try thinning out its regular racing oil with a mixture of qualifying oil to eke out slightly more horsepower. After running the experiment by Douglas and William, Mr. Speed got a warning from the two scientists. "You're scaring the hell out of us," they told him. The experiment worked, and one of the team's drivers, Kyle Busch, won.

Mr. Busch got most of the credit, but when asked whether he'd say the oil was a big factor, Mr. Speed responded "I would, because I'm the oil guy."

[BTM]

Originally Posted by Shipkiller

Just arrived back from the dealership where if I provide (I did) my own bottle, the standard SAF-XJ is $14.50 a liter. Two liters plus two new plugs had the total cost of $45.00.

The SAF-XJ w/FM Booster is $45.00/liter... That 'friction modifier' must be made of gold particles...

Don't think this was addressed... the XJ+FM (83 22 2 282 583) was part of a TIS to address diff noise at slow speeds / slow corners in E46 M3s and Z4Ms. It's just to quiet the diff down, and is otherwise no different than regular SAF XJ (83 22 1 467 993). So if you don't mind some diff whine the XJ sans FM is fine, as it's normal operation

[gcochard]

Not to derail the thread, but what would happen if you use a thinner oil like 75-90 in the diff?