hot weather fuel econmy

My truck loves the heat. Last tank mixed driving with AC on 20.5mpg. What a difference from the cold months.

 

1. Summer gasoline has higher energy content than winter gas. Winter gas is reformulated to have oxygenates added to help have complete combustion on cold starts for less emissions. Oxygenates are chemicals like ethanol that have lower energy density. Therefore, summer gas gives you more btu's per gallon.

2. Hot air is less dense (thinner) than cold air. This means you have to burn less fuel for the given volume (or rpm) the engine is breathing. Means you are burning fewer miles per gallon.

 

It's not the temp that does it, it's the fuel.
Well... Can't see where you live on my phone. In freezing areas they add up to 10% ethanol which absorbs water and prevents fuel line freezup. Ethanol has less power than gas=lower fuel econ.

 

Truck runs richer in the cold weather.

 

It requires the same amount of energy to move the truck. Less oxygen per volume means less energy per volume. You'd have to open the throttle more to get the same amount of energy.

Not true. Modern fuel controllers compensate for air temp and keep the AFR the same.

 

This.