Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

brucepick · 09-30-2011, 10:19 PM

I'm definitely of the opinion that the gradually decreasing temperatures this time of year do a lot to mask the effects of fuel blend changes. For all I know, the winter blends may actually give better mpg than the summer blend, if used under matching weather conditions.

I googled "winter fuel blend" and "winter blend gasoline", and learned a few things.

Most interestingly, it seems that the summer fuel is the blend that is a "revision" of the winter blend, not the other way around. Summer fuel must have a lower Reid Vapor Pressure, or RVP, otherwise it will boil within whatever container it is stored, at summer temperatures. I think this is what is called "vapor lock", and it's no fun when that happens to your vehicle. BTDT, over 20 years ago back in the old days. Given their choice, fuel blenders would provide "winter blend" year 'round because its ingredients are less expensive.

I found a reference stating that the shift to winter fuel begins on Sept. 15. It appears that this is the start of a gradual shift towards higher RVP blends, however I didn't find that explicitly stated.

Then there's the shift to summer fuel...
"...will require tank terminals to accept only summer grade RFG beginning
April 15 of each year... However, tanks at terminals must contain only summer grade RFG by May 1."

Here are some links re. summer/winter fuel blends:

A Primer on Gasoline Blending « EPRINC (a detailed article)

What's the difference between summer blended gasoline and winter blended gasoline? - Yahoo! Answers

HowStuffWorks "Why is summer fuel more expensive than winter fuel?"

HowStuffWorks "Summer-grade versus Winter-grade Fuel"

09-30-2011, 10:19 PM	#4 (permalink)
brucepick OCD Master EcoModder Join Date: Dec 2007 Location: Eastern CT, USA Posts: 1,936 Outasight - '00 Honda Insight Team Honda Gen-1 Insights 90 day: 54.18 mpg (US) Thanks: 431 Thanked 396 Times in 264 Posts	I'm definitely of the opinion that the gradually decreasing temperatures this time of year do a lot to mask the effects of fuel blend changes. For all I know, the winter blends may actually give better mpg than the summer blend, if used under matching weather conditions. I googled "winter fuel blend" and "winter blend gasoline", and learned a few things. Most interestingly, it seems that the summer fuel is the blend that is a "revision" of the winter blend, not the other way around. Summer fuel must have a lower Reid Vapor Pressure, or RVP, otherwise it will boil within whatever container it is stored, at summer temperatures. I think this is what is called "vapor lock", and it's no fun when that happens to your vehicle. BTDT, over 20 years ago back in the old days. Given their choice, fuel blenders would provide "winter blend" year 'round because its ingredients are less expensive. I found a reference stating that the shift to winter fuel begins on Sept. 15. It appears that this is the start of a gradual shift towards higher RVP blends, however I didn't find that explicitly stated. Then there's the shift to summer fuel... "...will require tank terminals to accept only summer grade RFG beginning April 15 of each year... However, tanks at terminals must contain only summer grade RFG by May 1." Here are some links re. summer/winter fuel blends: A Primer on Gasoline Blending « EPRINC (a detailed article) What's the difference between summer blended gasoline and winter blended gasoline? - Yahoo! Answers HowStuffWorks "Why is summer fuel more expensive than winter fuel?" HowStuffWorks "Summer-grade versus Winter-grade Fuel" __________________ Coast long and prosper. Driving '00 Honda Insight, acquired Feb 2016.