When doing a compression check, you want all of the cylinders to be within 10 percent of each other. If you have a low one, then it could be bad valves or rings. You would need to do a leak down test to further diagnose it. But, I think that the problem may lie with the computer. Did the check engine light come on? Has the oxygen sensor ever been replaced? The car may be stuck in a rich mode allowing more gas to be consumed than necessary.
Bob, The Auto Answer Man
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