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Debate: My 2015 Honda Civic went from 35 mpg to 28 mpg after 120,000 miles. Is that normal wear or a sign of something wrong?
I've been tracking gas mileage since new and it dropped exactly 7 mpg over the last 9 years. My mechanic says it's just carbon buildup, but my buddy's 2012 Elantra did the same thing. Has anyone else seen this big a drop with high mileage, and was it worth fixing or just the cost of aging?
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phoenix_carter3d ago
Daniel saying a compression test before and after the drop is kind of missing the point. Nobody does a compression test on a brand new car at 0 miles, so comparing that to 120k is pretty useless without a baseline. The real issue is that 7 mpg drop over 9 years is actually pretty normal for an older engine, especially if you’re not doing highway driving as much anymore. Carbon buildup is a real thing but cleaning it out usually only gets you back 1-2 mpg, not the full 7. I’d check your air filter, spark plugs, and maybe the O2 sensor before spending hundreds on a deep carbon cleaning.
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hugo8256d ago
Did your buddy ever figure out what caused it? My friend's Accord dropped 5 mpg and it was a bad O2 sensor.
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