jbell, For whatever reason, your engine and drivetrain are above average in efficiency. No two engines and fuel systems are exactly the same, some are better than others to one degree or another.

And, I suspect your driving ability is above average when it comes to fuel economy. Some people are more intuitive than others when it comes to driving efficiently. Gearheads and those who perform their own maintenance generally do better because they have a sense about their vehicle that others might not have.

Fuel quality can also affect fuel economy.

MP