Jeep mileage issues

Hey y’all. My car’s mileage has been getting worse, from about 16 mpg to 11 mpg. As well as the engine light being on and the gas cap sensor always being set off even when the cap is closed. There is also sometimes a slight gas smell on the passenger side of the vehicle after I drive the car (the gas cap is on the drivers side). Could this be a faulty fuel pressure regulator, or something else? Is it also safe to drive?

What year Jeep?


It’s a 2011


Get your OBDII codes read at a parts store and post them here. They’ll tell you why your check engine light is on.


The sensor says I have a minor/major EVAP leak. Bad for the earth, but less likely that I’ve been wrecking my car by driving it.

Have you had the codes read?

That’s what the codes said it was, EVAP leak

Please post the actual code, P0xxx, there are several Evap codes. How recently did you check them? Have you replaced your gas cap?

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Could be a fuel leak. That would explain an EVAP code, a fuel smell, and reduced MPG. A careful search from tank to engine is in order.

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My guess, the evap leak isn’t related to the mpg reduction. If that’s the only diagnostic code, common mpg reduction causes are

  • coolant is not reaching full operating temperature (often caused by faulty thermostat)
  • coolant temperature sensor used by computer isn’t accurate (causes computer to inject more fuel than needed)

Common sense diy’er tasks for something like this, new spark plugs, new engine air filter, oil and filter change, new pcv valve, and verify ignition timing is correct.

Good idea to fix that evap leak too. Problem is, leak could be nearly anywhere between the gas cap and the engine intake manifold. Best way to diagnose that sort of problem is using a shop’s smoke machine. Where the smoke comes out, that’s where the leak is. Could take a flyer on just replacing the gas cap, might get lucky.