This is great information. Get this, a month ago I had to buy a new tank cap. OEM, filled tank with coolant and drove from ME-FL about 1700 miles. Five days ago I was checking fluids.
That's when I noticed it was very low and filled it until the float stick came to the highest point. I also mistakenly over filled my oil by a pint during a change. Since these two updates I have clocked 1000 miles . Easily driving in the 2700-3200 rpm final drive. I am getting great mpg. Acceleration is flawless. Idles perfectly.
I even had to use AC yesterday. And sure enough, both the coolant and oil fluids remain exactly the same as five days ago. This is weird. If I were burning coolant some would be gone. I don't see any leaks. But I know my water pipes to block are original. Oh, no mayo on the oil cap. So I am going to check the plugs and try and get a compression test. If its all good, rebuilding the intake manifold side. Thanks for getting me started.

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X5 3.0 AUTO -2001 - 238,000 miles