You should be in the 18 to 24 mpg range, check fuel pressure regulator, common to leak gasoline into the vacuum line, next check air mass meter, either for codes or substitute a known good one those two items are usual suspects , car should run 20-50w oil, fuel pressure runs at 55 -58 psi,check thermostat should run just above 80c to 105 c normal range, tires pressures run 30 psi,