Should my mpg go up or down when it gets below 40* ? Mine goes down.
If more oxygen than is needed is provided, it doesn't make more energy - it only gets all the available fuel energy released. A given Fuel has a fixed amount of energy/gal. Winter fuel has less energy/gallon, so less energy is/can be produced per gallon. The ECU will adjust for this by controlling the fuel/air ratio to try to get the SAME energy for each spark. It injects a fraction more winter blend fuel to be burned to get the same amount of energy so that the engine can produce the target camshaft rotations per minute (horsepower). Hence, using more fuel to get the same energy results in lower mpg. Same thing sorta happens with going from 87 to E85.My brain is twisted on this... If there is more oxygen, and therefore more fire burning, wouldn't that create more energy with less gas? If the engine becomes more efficient at creating energy, doesn't that decrease the amount you need to press the pedal down? (even if it's an unnoticeable amount?)
Yes, and no, depending on whether you are talking about total amount of energy released, or net energy output of the engine. Yes, the total (gross) energy is the same, but net output of the engine is different when a smaller throttle opening is necessary when the air is colder. Energy is used to pull air through the throttle. Smaller throttle opening requires more energy. This is commonly referred to as "pumping loss", and more specifically, the component of pumping loss caused by part throttle operation.X ounces of fuel compressed with the correct mass of air gives So much energy. It doesn't matter where your foot is on the throttle
Live in "Splendid" Ca, with its to die for fuel blends. In the winter with stock tires I get 14.8 mpg! I had this argument with my older twin brother(9 min) he was adamant about it going up. I had to show him multiple times. He has an ego with it's own social security number.The air is more dense, you are taking in more oxygen. With that, you are burning more fuel. If you are in a region that switches to a winter fuel blend, it's even worse.