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Discussion Starter · #1 ·
So I headed out today for Charlotte to visit someone in the hospital...it is about 240 miles round trip. Since getting my '95 VT600 a couple of months ago I typically get in the 53-55 mpg range. Part way there I needed to stop and fill up...I got 2.44 gallons and that tank averaged 57 mpg. Less than 100 miles later i had to switch to reserve so i pulled over and filled up again, this time getting 2.1 gallons which means I averaged 47 mpg. When I got back home I decided to top off my tank, which took 1.8 gallons meaning that tank got 45 mpg. So in short my last three tanks averaged 57, 47, and 45 mpg.

My riding today was some city but a lot of interstate. Granted this morning I was going down the mountain which certainly would have helped the mpg and this afternoon the last 40 miles was coming up the mountain, but that still seems like a pretty drastic drop...more than I have noticed before.

Any thoughts as to what would cause the mpg to seemingly drop all of a sudden? My speed much of the day was probably 65-70, I tried to keep it around 60-65 once I noticed that my mpg was dropping. Up here where I am the temperature has been in the low to mid 80's while in Charlotte it was probably pushing 100...not sure if that would affect things or not.

Any thoughts/suggestions are appreciated. thanks.
 

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They change the formula for fuel in the summer to cut down on emissions. It kills the mileage. I have a Nissan pathfinder also and it drops about 2-3 mpg every summer.

The biggest changes in the fuel formula is around metro areas. You probablyt were getting more ethanol in it also.
 

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My 84 VT700c had a rather dramatic drop in mileage with the FUEL light coming on at 56 miles instead of 112, what ended up being the most noticeable problem was that the main fuel hose between the main and sub-tanks was loose and was leaking fuel that was being sucked down a hole behind the engine and seats so that I could never smell it.

So my light is coming on now at 100 miles I think the carbs are still waking up from their winter slumber (it has been raining here since November).
 

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Discussion Starter · #7 ·
landon,

did it leak only while running or do you think it leaked all the time? I neither smell gas nor have been able to find any indication of a leak.

In relation to the ethanol, maybe I'm missing something--admittedly this is NOT my area--but since all the places I purchase gas from sale ethanol, then it seems to me unlikely that this would be contributing to this sudden decrease in mpg? Not sure if this is so, but that is how my logic works.
 

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I believe that mine only leaked while I was riding it and after things warmed up and I never smelled it in the garage, it was bad enough that (according to the math) I was burning / leaking a gallon of fuel about every 28 miles.

Ethanol is mandated everywhere in Oregon for motor vehicles also, it used to only only be during the winter but it is all 12 months of the year now, my mileage dropped 10% and has stayed that way ever since so your problem is probably not related to ethanol if it just suddenly dropped out of the blue.
 

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landon,

did it leak only while running or do you think it leaked all the time? I neither smell gas nor have been able to find any indication of a leak.

In relation to the ethanol, maybe I'm missing something--admittedly this is NOT my area--but since all the places I purchase gas from sale ethanol, then it seems to me unlikely that this would be contributing to this sudden decrease in mpg? Not sure if this is so, but that is how my logic works.
Endy is probably right when combined with your mountain rideing, but to answer the ethanol question. In metropolitan areas they formulate the gas even more poorly. When combined with the fact that with much more gas going through the stations tanks, you have more oppurtunity for the ethanol concentration to build up in the tank. So the gas you get in Charlotte is lower quality than in the small towns 2 hours away. Recently I drove from San Antonio to Little Rock in my pathfinder. I got 22 miles/ gl all the way to dallas. Filled up there and got 16.8 until that tank ran out.
 

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Up where I live, Shell and Esso are ethanol free. I was in Hamilton (100 miles away) and filled up with ethanol fuel. What a difference on the ride home. Popping on decel was disgusting. Should have drained the tank when I got home.
 

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So I headed out today for Charlotte to visit someone in the hospital...it is about 240 miles round trip. ... Part way there I needed to stop and fill up...I got 2.44 gallons and that tank averaged 57 mpg. Less than 100 miles later i had to switch to reserve so i pulled over and filled up again, this time getting 2.1 gallons which means I averaged 47 mpg. When I got back home I decided to top off my tank, which took 1.8 gallons meaning that tank got 45 mpg. So in short my last three tanks averaged 57, 47, and 45 mpg.
According to my calculations using the posted data:

6.34 gallons for 240 miles = 37.8 mpg. trip average (assuming full tank to start).

If the tank was not full to start, the first tank was partly used under different riding conditions - perhaps more favourable than high speed highway riding.
 

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Discussion Starter · #17 ·
According to my calculations using the posted data:

6.34 gallons for 240 miles = 37.8 mpg. trip average (assuming full tank to start).
Yea, did not begin with a full tank, so at least half of that tank was under different riding conditions. It still strikes me that there was SUCH a difference. I have always averaged between 51-55, so it just caught my eye and got me wondering.
 

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I'm a former 20 year resident of Charlotte. Air quality issues there, vehicle inspections became extremely strict on emissions in Mecklenburg county in the 90's. Charlotte is between the mountains and the ocean, air gets stuck there. The combination of vehicle concentration, high humidity and stagnant air makes it miserable there on hot days. Ozone levels are regularly in the "unhealthy" levels in the hot months. If there was ever a place where the gas would be tweaked for emissions and you'd have poor quality air being pulled into your engine, it'd be the Charlotte area.
 
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