Some posts recently have claimed that MPGs are affected by a change in the quality of fuel about now from a summer grade to a winter grade. I'd never heard of such a change. Is a difference admitted by the oil companies or is there some real good evidence to support it? I have a suspicion that this is an urban myth but if it is true are fuel supplies in other countries also changed winter/summer?
i read that there are over 30 blends of gasoline used around the country in the summer time and slightly less variety in the winter time. summer gas freezes at a relatively high temperature. so anti-freeze components need to be added to lower the freezing point. these additives dont burn but do take up space. that effectively gives you less gas per unit of volume resulting in poorer gas mileage.
Seems like an excellent answer to the question. Thanks to Marlin and DaveinOlyWA. PriusChat has again shown what a very good service it is!
