2003 nissan alitma MPG

[jvmagic]

Hi,My 03' altima gets 23.2 -23.5 MPG. I do have a service engine code of 507 (or something like that) every once in awhile.....which makes my car idel weird (high)....I can understand this making my car not run as efficient as possible but my sister-in-law owns the exact same model (03' 2.5 litre altima) and she is getting 29.3 MPG. She drives a bit more freeway (not much) but still...the difference is quite a bit. what can I do? what do you get for MPG??

thanks in advance,

~julio

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