Regional differences in fuel blends?

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Hello everyone. I am wondering how drastically fuel blends vary from region to region. I never thought much about it until I noticed that I get much more MPG in North Carolina than I do here in Tennessee. Last Fall I took a trip to North Carolina to go visit a friend and I noticed that I get much better gas mileage in North Carolina than I do here in Tennessee. Here in TN I often see around 29 MPG doing mostly highway driving and I have seen as high as 32 MPG, but that only happens here with almost all highway driving and a very light foot.

But after I drove to North Carolina, I noticed that I was getting significantly higher MPG. I went through 4 tanks of gas in the week that I stayed there and I averaged about 37 MPG with my worst tank being 36 MPG (fair amount of traffic) and my best tank was 39 MPG, which is way better than what I am used to getting. I was initially thinking that the higher MPG I was seeing was because the 600 mile highway trip may have cleaned up the engine, but that was not the case since my gas mileage dropped down to the normal high 20's to low 30's as soon as I was back home and I have yet to see that many MPG since then.

I can not think of any other variables that could account for such a large difference. AC usage was not a factor as the weather was not warm enough to need to use it and my driving style was the same as usual. I filled up at the same gas stations I normally do (Shell, BP, and Exxon) and I used 87 octane with Marvel Mystery Oil as I always do.

After that, I started researching fuel blends and I found that there are many different fuel blends used in different regions and I learned one potentially significant difference: MTBE is banned in NC, but it is legal and possibly used here in TN. From the research I did I found that similar to ethanol, MTBE has a lower energy content than gasoline and therefore causes some reduction in MPG compared to pure gasoline. However, I don't see just MTBE reducing my MPG by such a significant amount.

Do any of you know how significant the differences in fuel blends are from region to region? Possibly there are other differences as well that could account for some of the difference in MPG that I experienced? Also, have any of you experienced any differences in MPG between different states/fuel blends?
 
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Things that may come into play...

#1 would be ethanol content of the fuel (lots of posts on this if you look around here)

#2 would be driving habits. If you were on a vacation and driving in a much more sedate manner, then you will see much better MPG. Just thinking about my own habits...if I am going to and from the store or to and from work, I drive to get the task done. When I am driving on vacation, I don't always know exactly where I am going, and I am taking in the sights...so I slow down.

I am guessing it is either of those, or combo of them together...but for further discussion...

There are different Reid Vapor Pressures by state and by month that can change the energy content of your fuel, but not by the amount you are seeing.

Elevation - you were at a lower elevation, which normally makes fuel economy decrease (worse).

Temps? Not sure if there was a drastic change in your temps

I don't know that MTBE is allowed in any fuel in any state today...but I could be wrong.
 

Avery4

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Things that may come into play...

#1 would be ethanol content of the fuel (lots of posts on this if you look around here)

#2 would be driving habits. If you were on a vacation and driving in a much more sedate manner, then you will see much better MPG. Just thinking about my own habits...if I am going to and from the store or to and from work, I drive to get the task done. When I am driving on vacation, I don't always know exactly where I am going, and I am taking in the sights...so I slow down.

I am guessing it is either of those, or combo of them together...but for further discussion...

There are different Reid Vapor Pressures by state and by month that can change the energy content of your fuel, but not by the amount you are seeing.

Elevation - you were at a lower elevation, which normally makes fuel economy decrease (worse).

Temps? Not sure if there was a drastic change in your temps

I don't know that MTBE is allowed in any fuel in any state today...but I could be wrong.
Thank you for your input!
1. Never tested the ethanol content of NC fuel, but the fuel here in TN has right at 10% ethanol at the 3 stations that I use. Even going from 10% down to 0% ethanol would only get me about 1 extra MPG from the research I did and none of the fuel I used while in NC claimed to be ethanol free.

2. Like I said I drove about the same way I normally do. I used to live in that area, so I knew the roads very well. Also, driving habits could not account for all the difference because even if I drive as gently as possible I only can get about 32 MPG at the most here.

Elevation where I was is about 400' higher in NC than at home, which would theoretically improve MPG by some small amount by reducing pumping losses and aerodynamic drag. However, although I doubt that a 400' change would be something I would see in my MPG by itself, it could account for some of the change I saw. Temps were not significantly different. However, I was at a small disadvantage while in NC because I was not able to park in a heated garage like I normally do, meaning slightly longer warmup times from cold starts.

I did not know about the fuel blends changing by the month, I thought there were only 2 blends (winter and summer). Do different states require different blends?
 

Avery4

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Different regions/metropolitan areas have different RVP requirements. It varies from state to state and time of year.
Good to know, thank you for the information! How much could the different blends effect MPG? Obviously changing the fuel blend would have some effect, but would the difference be slight or drastic like what I saw?
 
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Good to know, thank you for the information! How much could the different blends effect MPG? Obviously changing the fuel blend would have some effect, but would the difference be slight or drastic like what I saw?
Could be. The numbers you stated aren’t large enough to point to any one thing. Just something like the texture of the road surface could cause it along with numerous other things.
 

Avery4

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Could be. The numbers you stated aren’t large enough to point to any one thing. Just something like the texture of the road surface could cause it along with numerous other things.
Yup, the roads are another factor. Where I live the roads are terrible compared to in NC. There are lots of rough roads, bumps, and potholes, which would have to effect gas mileage to some extent. How significant that would be I have no idea and no way of testing.
 
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MTBE has a very distinct odor. It smells a lot like wintergreen. MTBE isn't super toxic or anything, so don't worry too much if you get a whiff.

I'm not sure whether or not it would be common. MTBE has certain advantages - the most important would be that it can be transported by normal petroleum pipelines. However, the most common commodity fuel (RBOB) is meant for 10% ethanol blending.

There are just way too many variables with most commodity fuels. Sometimes just the particular blend of crude oil can affect the energy content of the fuel made, and it's not something that's terribly well controlled.
 

Avery4

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MTBE has a very distinct odor. It smells a lot like wintergreen. MTBE isn't super toxic or anything, so don't worry too much if you get a whiff.

I'm not sure whether or not it would be common. MTBE has certain advantages - the most important would be that it can be transported by normal petroleum pipelines. However, the most common commodity fuel (RBOB) is meant for 10% ethanol blending.

There are just way too many variables with most commodity fuels. Sometimes just the particular blend of crude oil can affect the energy content of the fuel made, and it's not something that's terribly well controlled.
Thanks for the information! I didn't notice any wintergreen smell from the fuel, so perhaps they are not using MTBE. I do know that some fuel blends are horrible for MPG though. When I lived in Ohio there was a particular BP station by my house that I didn't use because I consistently got worse MPG when using their fuel. Using their fuel would consistently drop my mileage from around 29-30 MPG down to 23-24 MPG and I verified that over several tanks. I wish I had my Scangauge at that time so I could see what that fuel was doing to my air fuel ratio and fuel trims.
 
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Thanks for the information! I didn't notice any wintergreen smell from the fuel, so perhaps they are not using MTBE. I do know that some fuel blends are horrible for MPG though. When I lived in Ohio there was a particular BP station by my house that I didn't use because I consistently got worse MPG when using their fuel. Using their fuel would consistently drop my mileage from around 29-30 MPG down to 23-24 MPG and I verified that over several tanks. I wish I had my Scangauge at that time so I could see what that fuel was doing to my air fuel ratio and fuel trims.

MTBE does have certain advantages. It's not as oxygenated as ethanol, but it has more energy content. But they typically use up to 15%, which almost any car made in the last 40 years can handle. I don't believe it phase separates as easily as ethanol.

Have no idea what your issue is, but I wouldn't necessarily chalk it up to MTBE or ethanol.
 

Avery4

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MTBE does have certain advantages. It's not as oxygenated as ethanol, but it has more energy content. But they typically use up to 15%, which almost any car made in the last 40 years can handle. I don't believe it phase separates as easily as ethanol.

Have no idea what your issue is, but I wouldn't necessarily chalk it up to MTBE or ethanol.
Yup you are correct. As I said, the difference I saw was too large to be explained by MTBE or ethanol alone. One big problem with MTBE is the potential for causing significant water pollution problems if it leaks, which is why it is banned in many states.
 
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Yup you are correct. As I said, the difference I saw was too large to be explained by MTBE or ethanol alone. One big problem with MTBE is the potential for causing significant water pollution problems if it leaks, which is why it is banned in many states.

The water pollution issue is more of palatability. It's not terribly toxic in the amounts that most people would encounter, but it does make water foul tasting.
 

mez

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I often drive from Boston, MA to Southport, NC. I fill in Boston, NJ, VA and NC. By far VA gas station gets me the highest MPG followed by NJ. I done this round trip once a month and VA consistently gives best MPG. Not sure why either. I get 1-2 MPG more in VA.
 
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There are some regions where the gasoline blends don't change at all. All the fuel that I pull is the same year round. The fuel that comes from our local terminal is distributed to nearly 99% of the entire Northeastern part of GA. Down in N Augusta, SC...the blend is the same year round. Those terminals cover and even larger region than my local terminal. We're talking most of SC, and a lot of Southeast GA.

However, most of the fuel that comes out of Doraville GA is seasonal which supplies most of the 13 metro counties that have emissions requirements.
 
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There are areas that because of EPA air quality non attainment have a "reformulated" gasoline to reduce emissions.

Houston Tx is one of those areas, When traveling to Indiana from Texas I would always get less MPG on the tank from Houston than I did on the rest of my trip. Stayed the same over about 5 years of traveling back and forth. It was only about 4 mpg difference.

Here is the 2018 US gasoline requirements -
2018 US Gasoline requirements

It looks like both Tenn. and N.C. have conventional gasoline statewide.
 
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