|
Winter gas blends use more of the cheaper, more volatile hydrocarbons like butane that burn better when cold but also contain less chemical energy. This is why there is a slight drop in price and mileage that occurs when they switch to the winter blend. The purpose of different winter and summer blends is primarily for evaporative emissions; summer gases must use the less volatile, more expensive blends which don't evaporate as quickly in the warmer weather.
This has also been consistent with my experience. Over 138 tanks in our Scion it is pretty easy to pick out the exact first tank when the gas stations switch from summer to winter gas and vice versa. Our average over 26 tanks this summer was 31.3 miles per gallon, and in 10 tanks since the end of September our average has been 28.2 miles per gallon, about 10% less. From May until October we only had one tank below 30mpg, and since then we've only had one tank above 29mpg.
All brands make the switch. It is required on May 1st and September 15th every year, but I think sometimes the switch can be made earlier.
|
Linear Mode
