Here's my cluster now:
It is a 135i cluster that came off a car with 89k miles. I think it was an '08, but I'm not sure, it was $99.
After tearing into it, I found that the EEPROM was the same model (080D0WQ) as was on my 128i's cluster. I then thought, heck, I'll just swap the EEPROMs around since they're the same model, they must communicate and work the same way. They did, and everything worked right off the bat; odometer, tacho, speedo, fuel, but the oil temp needle was indicating the instant MPG.
I then delved into Google, and found a few E90 threads about people wanting to change the MPG gauge into an oil temp gauge. I followed the coding instructions, using Tool32, and ended up with a successful code, and it was all done.
Here's a link to a Google Doc I was typing up for my DIY (which I pretty much just wrote here):
https://docs.google.com/document/d/1...it?usp=sharing