15-18 would be regular. Remember, the EPA standards are not actual driving standards because people drive differently and states have different speed limits. There's usually a disclaimer that says "Actual mileage may vary".
Usually, trucks/suvs/heavy cars get less mileage in actual driving conditions while other cars get more. I get 35-38 on the highway and my original estimate was 26 (25 in city estimate was 22). So...yeah...it's common...and complete B.S. in my opinion. What matters is your fuel mapping and fuel quality. Honestly, most companies fake the testing by changing the tune (usually leaner) in test vehicles then make it richer for the mass produced tune to reduce warranty claims.
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