i went to shops, and i couldn't find anything about this problem in a forum. i have a d16z automatic that is getting 155miles to a tank of gas. i change the spark plugs, oil ( 4 times in 3 weeks), air filter, and fuel filter and i'm still getting from 155 - 170 miles to the gallon. right now the only other problem i have with the car is the master power(brake booster), it makes a sucking sound when i turn it on and for a few seconds after i turn the car off. does that have anything to do with fuel economy? and what else can i do to solve this problem?