530i Resonance

I have a BMW 530i model sedan with automatic transmission which has an annoying resonance that appears primarily at around 45 mph in 5th gear. It is worse after the engine warms up. I can avoid the issue by driving in
sport mode; however that hurts the gas mileage. Any ideas on how to fix this problem? Thanks.
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JB
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Steve Cooper wrote:

Not a direct answer to your question, but I'll bet driving in "sport mode" doesn't hurt your gas mileage as much as you might imagine. That is unless you use your right foot with more gusto whenever in sport mode too...
My point is, just driving in a lower gear and spinning the engine faster may or may not hurt mileage.
--
-Fred W

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Where does the sound seem to be coming from?
Perhaps a higher RPM in sport mode is making a muffler problem evident.
As for poor MPG, I'll second that opinion about poor mileage. The difference is minimal. I ran three, full tank tests on each of sport mode & Non-sport mode. Mileage didn't vary more than one mpg at best.
You're missing the fun if you don't use sport mode.
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