I posted most of this in another thread, but thought it was interesting. Any petroleum engineers out there know definitively what's up?

Bottom line: from 1995-2000, there was minimal or zero difference inOxygen content or chemical additive makeup (MTBE/ethanol mix) between winter and summer fuels in almost every region sampled!

Most places (fewer now) use MTBE, or MTBE+ethanol to achieve 2% O2 and thus a ~1.5% FE hit. Some areas use E10, resulting in 3.5% O2 and a ~3% FE hit. You can see the evolution of some areas (WI and IL) away from MTBE towards E10 in the tables.


full 1997 Congressional report( chap 3 deals with FE):
http://www.epa.gov/otaq/regs/fuels/ostpfin.pdf

details of 95-00 analysis of RFG sampling:
http://www.epa.gov/otaq/consumer/fu...e/oxy-95-00.pdf


I know what the stickers on the pumps say, but it appears that the economics of using a single blend year round have won out. I guess if there's nothing in the local code that prohibits the sale of winter blend in the summer, its easer/cheaper to just make the more restrictive blend all the time.

Perhaps the mpg hit from "winter fuel" is in our head, or solely due to temp.

Thanks for posting these links. I have always heard about this fuel blend stuff, but I could never find any definitive information about it. And since none of the pumps I have visited have any stickers indicating a different blend, I have begun to wonder about the validity of the 'winter fuel' premise as well.

Hi GoNavy:

___Here in Illinois, we haven’t had even a trace amount of MTBE in years but it is mandated by law that we use E10. I am not saying this is an entirely bad thing because of its homegrown nature and GHG reduction but given it is corn based, it is a mistake for the loss of my FE and the overall Fuel’s actual attributes used from field to wheel … Your links bare the lack of MTBE out here in the Chicago area. There is a chemical difference between winter and summer blend RFG here (VOC and vapor pressure differences abound) in Northeastern IL. and Southwestern WI. It is in the gasoline formulation, not the Oxygenate additive that makes all the difference.

RFG Property and Performance Averages for Chicago-Lake Co., IL, Gary, IN

Information on Reformulated Gasoline (RFG) Properties and Emissions Performance by Area and Season - Methodolgy and Explanation

___Not only do us Illini get hit with E10 and Winter blend RFG, we also get hit with cold temps which is by far the hardest on everyone’s FE here in the Chicago area this time of year I will not even go into the garbage high sulfur stuff we are forced to use. I think the EPA allowed the refiners to push HS fuel to the Milwaukee – Chicago – Gary corridor because of the prevailing Westerly’s diluting it out over Lake Michigan possibly? I would love gasoline from just about anywhere else but “dem der is da breaks”

___Good Luck

___Wayne R. Gerdes

thanks. I've got an incomplete understanding of the topic.

My confusion was in the interchanged use of "oxygenated" fuel and "reformulated" fuel. That, and here in MD the pumps have stickers that say fuel between Nov-April is oxygenated- nothing about the summer. Even though we are in the RFG program.

This is what I get for not doing thorough enough background research.

To clarify for those whom I have succeeded in confusing:

RFG is mandated in smog-prone areas. RFG requirements have a few parts:

1) All fuel is oxygenated to at least 2% year round. So that MPG hit is a constant in your local area.

2) Summer fuel is required to have a lower vapor pressure...less of it evaporates. That means it is literally heavier, has larger molecules, usually with more energy content --> better mpg.
So winter fuel is in fact different, but not in oxygen content. It evaporates more easily, ignites more easily (important when its cold), but has less energy content.

3) other toxins must be reduced as well (Benzene)

Sorry to raise a false flag.