2002 Lexus ES 300
 

Have driven my mom's car on many trips & best I ever got on the highway was 27. Switched from 5w30 to 0w30 oil & pumped up the tires to 42 PSI. Drove about 800 miles this weekend & averaged 29.3 (with 2 extra passengers to boot) Astonished this was possible with a semi tank category vehicle with a good bit of stop & go mixed in.