N51 Oil Pan Question: 6MT vs Auto

[jmciver]

I recently purchased a high mileage (145k+), 2009 128i 6MT that I plan to give to my high school age son. It is a SULEV car with the N51 engine. I did my research on the car (thanks to the great info in this forum) and I was prepared to address the typical issues for this model based on my pre-purchase inspection, in particular the VCG, OFHG and Oil Pan gasket. My question pertains to the oil pan.

Upon my inspection of the oil pan it is an aluminum pan, which did not seem abnormal. When doing some research to order the correct parts for the oil pan gasket job (on the forum, newtis.info and RealOEM) I learned that the aluminum bolt set for a 6MT car is different than the aluminum bolt set for an automatic. Again, nothing really abnormal. But here is where it gets weird...

During my parts research, I happened to stumble upon the fact that the oil pan on the 6MT cars are steel (painted black) while the oil pan on automatics are aluminum (based on oil pan pictures from ECS and FCP Euro). They both have different part numbers as well. Now here is the weird part, the oil pan on my car (which is a 6MT) is clearly aluminum. WTF??

So I guess my initial questions are....

1) Did cars with the N51 & 6MT ever come with aluminum oil pans (which is contrary to what is in RealOEM - it should be steel)?

2) Are the steel oil pans (for 6MTs) and the aluminum oil pans (for autos) interchangeable on the N51, regardless of transmission?

I just ordered oil pan gasket parts for the car - with 6MT aluminum bolts. But I am wondering if I need to order the aluminum bolt set for the auto since I know some of the bolts are of different lengths for the aluminum pan. The car runs fine, shifts fine and other than the typical N51/N52 oil leaks is in very good condition for the age and mileage. I just want to make sure I am ready to do the oil pan gasket job before I take everything apart.

Thanks!

[JimD]

I drive a 2009 e88 with a n52 and a manual transmission. I am pretty sure the oil pan is aluminum. It also dumps straight down. My ex-wife's 2013 e88, n52 with automatic, shots out sideways. I've changed the oil on both and the pans of both both looked and acted like aluminum, not steel.

I do not know how you searched realoem but I would be careful specifying your vehicle and see what you get. I think you can input the VIN. It might be true that some N51s or n52s had steel pans but it seems very odd on an aluminum/magnesium block. The thermal coefficients of expansion are quite different making it more challenging to get a good seal. Steel pans are in my experienced stamped and not meant to see significant stress. The pan area of the n52 seems designed for the pan to be helping to keep the bottom end together -like it sees stress. I am finding it hard to believe any of these engines had stamped steel pans.

I looked up the oil pans of my guess of your n51 (it wants build date) and my n52 in RealOEM and I agree, the pictures seem to imply that the oil pan can be either steel or aluminum. I did not see where it says that but that is what the pictures look like and I don't see any other obvious reason for there to be two listed. Seems odd to me. Steel would seem to be obviously cheaper. Why did they use both? You might have to crawl under there with a magnet and see what you have.

[jmciver]

My car is a 2009 128i 6MT E82 (w/N51) with a build date of Nov 2008.

I know for a fact that mine is the aluminum one (I had my car on a lift this weekend with the underpanels removed looking at other stuff). The color is clearly aluminum (like my other BMWs I own) and the oil dumps to the side, not to the bottom like on the steel pans. I also know my way around RealOEM (including when sometimes RealOEM gets it wrong - which is pretty rare) - but I will go back in with my specific VIN to see if I may have missed something.

This is the aluminum pan I have here:

https://www.ecstuning.com/b-genuine-...n/11137552414/

This is the steel pan a 6MT E82 128i car is supposed to have according to RealOEM:

https://www.ecstuning.com/b-genuine-...n/11137553164/

I agree with you about it being weird to have a steel pan. I have never seen one on my other BMWs (past and present): E36 M3, E46 M3, E83 X3, F25 X3 and F80 M3. In fact, the only place I have seen a steel oil pan was in an oil pan gasket DIY thread on E90Post, which was a 2006 E90 325i 6MT with N52 engine. I didn't pay much attention to it until I realized I had an aluminum pan when RealOEM says I should have a steel pan.

Here is the oil pan gasket DIY thread I am referring to. That oil pan on that car is clearly the black steel one:

https://www.e90post.com/forums/showthread.php?t=1180020

Makes me wonder if the pan may have been replaced by a previous owner (I am the 3rd owner according to CarFax). I forget where I saw it mentioned that the 6MT pan is steel - I guess it could be an aluminum pan painted black. But the pan on my car looks nothing like the pan called out for my car in RealOEM for a 6MT with N51.

[jmciver]

So I went back into RealOEM using my VIN and came up with the same oil pan options for the N51: steel pan for 6MT and aluminum for Auto. Any ideas? It actually would not surprise me if the aluminum pan is compatible, but just not documented properly in RealOEM (I have seen this type of thing before).

It would be great if someone else could verify they have the same oil pan though so that I could be sure (or at least verify if the two pans are compatible with a 6MT car) ......

[jmciver]

So a quick follow-up for those who are curious...

I was able to get under the car this weekend and re-confirmed that my 128i (N51 SULEV), a 6MT, does in fact have an aluminum oil pan. It looks just like the aluminum oil pan that comes on the auto N52's. See pics below...





So based on this I have come to two possible conclusions about this car...

1) This car is a "unicorn" from the factory where BMW put aluminum oil pans on a limited number of early model 128i's w/6MT and this uncommon configuration is not captured in RealOEM (I have seen this before). Maybe this is unique to the N51/SULEV engine ....??

2) One of the previous owners replaced the original steel oil pan (due to damage, etc) with an aluminum pan from an auto since it appears the aluminum pan bolts right up to the 6MT. I noticed that used 6MT N52 steel oil pans were significantly more rare than used auto N52 aluminum oil pans.

When doing some further research online, every picture of a 6MT N52 on an E90 had the steel oil pan. I only found a few pics of 6MT 128i oil pans installed - which were also steel. But those few pics were from cars that were 2010/2011 MY, my car is a 2009 MY (with 11/2008 production date). Regardless, based on what I can ascertain, it appears the aluminum and steel oil pans are interchangeable, regardless of transmission.

Makes me wonder why BMW used a steel oil pan only on (most of) the 6MT N52 cars. The stamped steel ones are obviously cheaper to make, but given the overall new retail price of the cars that used the N51/N52 engines, I am surprised it would make that much of a difference.

I ordered a set of auto oil pan screws since it appears to be applicable here for when I tackle the oil pan gasket very soon.

[JimD]

I changed my oil over the weekend and out of curiosity tried a magnet on the oil pan. To my surprise, it is steel. I made sure I was on the pan, not the drain plug. I have a 2009 e88 n52. I thought it was aluminum but I am wrong. I like the fact that it dumps straight down. It also makes me a little less nervous about the fact that BMW technicians buggered the threads a bit during the time they were doing the "free" oil changes. It has smoothed up with me changing the oil. But steel threads have greater strength than aluminum ones so a little damage doesn't mean as much.

Still curious that they put a steel pan on an aluminum block apparently with aluminum screws. The screw part makes sense, the pan is threaded to the screws, but the pan will expand less than the block making it more difficult for the gasket to prevent leakage. But I use no oil, at least by the time of my oil change - at 5K miles, just for convenience.

[jmciver]

So I thought I would close the loop on this one a bit..... I completed an oil pan gasket replacement job on my 6MT 128i and I used the procedures for the auto trans cars with the aluminum oil pan, including using the oil pan bolt kit for cars with aluminum oil pans. Other than the fact that all technical literature I could find states that I should have a steel oil pan due to my car having a 6MT, the oil pan gasket job went fine.

The only other evidence of 6MT cars coming with an aluminum oil pan that I found was in a thread for a clutch delay valve (CDV) mod. The OP of the thread took pics of his CDV mod, and in the pics I could clearly see that he also had an aluminum oil pan. I am not sure what year the car was or if it were a SULEV car or not (my car is SULEV). And the car in that thread looked almost brand new so I doubt the oil pan was replaced/swapped out.

So I guess the moral of the story is, check your oil pan ahead of time to ensure you don't have a "unicorn" like mine. It is nice to see that the two types of oil pans seem to be interchangeable, which is a good thing should you need an oil pan replacement. FWIW, I prefer having the aluminum pan anyway.

[JimD]

I learned something (i.e. my pan is steel) during this thread.

jmciver, does your oil come straight down or at an angle when you pull the oil drain plug? I am pretty sure my ex's pan is aluminum and when I changed her oil, the oil came out basically horizontally. I had to make a deflector (our of carboard) to avoid a mess. But the oil from my steel pan comes straight down.

I am wonder if the way the oil comes out of the pan may be a good indicator of the pan material. I think I have a slight preference for an aluminum pan on an aluminum block but if the steel one has the oil coming out "right", that would shift me the other direction.

[jmciver]

It comes out to the side. See post #5 above where I posted a pic of my oil pan ... But you are correct, the drain plug on the steel pans points down, the aluminum ones point to the side.

[$iriu$black]

So, from reading this post, is it safe to assume that if your car came with a steel pan (I believe all MT cars, do, except for the OP), you CAN install an Aluminium pan with NO issues? Or am I missing something?

Mine def needs an oil pan replacement and debating if I can try out an Aluminium pan instead of the steel version.

[Dackelone]

ALWAYS order parts via your VIN number.

I would use RealOEM.com to see which part your car has.

Dack

[motopsycha]

I'll add a data point. I have an 09 N51 MT. It has an aluminum pan.

[$iriu$black]

Originally Posted by motopsycha

I'll add a data point. I have an 09 N51 MT. It has an aluminum pan.

So some have the steel and some have the AL pans. According to REALOEM MTs have the steel pans and the ATs have the AL pans, though it may still differ with some models who have otherwise. These are probably a rarity. My prod date was 7/11 for a ‘12 if that matters.

[jmciver]

Originally Posted by Dackelone

ALWAYS order parts via your VIN number.

I would use RealOEM.com to see which part your car has.

Dack

I did, and RealOEM pointed me to a steel pan even though I have an aluminum one...

And here is the link to the CDV mod thread I referenced above. When you look in the pics he posted, the car clearly has an aluminum oil pan too....

CDV Delete/Replacement DIY https://www.1addicts.com/forums/showthread.php?t=209440

[JimD]

It isn't worth the considerable effort unless you are changing the gasket but if you change your own oil, it could be worthwhile to put on a steel pan. Having oil shoot out horizontally isn't a great idea. I put a quarter turn ball valve on a SUV I used to have that did this and a short hose so I could direct the oil down. I don't think there is space to do this on a 1 series, however. I think an aluminum pan on an aluminum block is a nice combination but if the steel pan provides straight down oil extraction plus steel threads for the drain plug, it has advantages.