It just so happened I saw a E30 325i, and a 525i for its time, and their dash look the same. I would think cars with similar engine size use the same dash would probably do the job and lower costs. Then again, they probably want to furnish a more upscale environment in higher models. (I don't mind sharing the dash with 640i
)
Both dash show only water, no oil. I would start worry about water and oil (if it's there) if it moves off the center, since there are no numbers.
Funny thing is that, if you buy the (very expensive) supposedly M steering wheel or whatever they call it, the water and oil temperature are shown directly in front along with rev counter lights. They have also fit dry sump oil system in 135, so it seems they recognize the need for it. It almost feel like they know but just want money for it.
Or it may just be one of the mysteries we will never find out
Thanks gents for all the answers.
Sincerely,
Charles