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Watch out- gas stations 10% different in MPG

Discussion in 'Prius c Fuel Economy' started by NewYorkan, Jan 27, 2014.

  1. NewYorkan

    NewYorkan Junior Member

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    I took a trip with ford focus from NY to Florida. Here is what I found.
    2 gas stations gave 40-42 MPG. (No brand name gas station with good price)
    2 gas stations gave 34-36 MPG. (One of them was a big brand name. Forgot which one)

    Last gas station, Mobil, my favort gas station. I drove further (skip couple gas stations) and paid 10 cent/gal extra. I got only 36-38 MPG. I was so mad.

    1. So, if you paid lowest price, but lose 10% in mpg. You lost. Just imagine that you paid for 10 gal of gas, but you got only 9 gal. Lowest price won't make up for that.
    2. If you buy from big brand gas, you are still at risk.
    3. With the Focus, it is not a hybrid car, so it is more consistence. It is easier to tell MPG. The Prius will be harder to tell which gas station is better.
     
    #1 NewYorkan, Jan 27, 2014
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    E0 will be about 3 to 4 % higher MPG than E10.
    E0 will be over 25% more MPG than E85.

    I do not see the kind of rigor Bob Wilson put into his testing to be sure he would have gotten identical mileage with identical gas. Brand Name Top Tier gas advertises that they put in more cleaning agents so it will be slightly less pure gas than gas without detergents, this helps long term, but may be less MPG on one tank.
     
    #2 JimboPalmer, Jan 27, 2014
  3. bisco

    bisco cookie crumbler

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    were these all on 95? we've been traveling to florida for ten years and never experienced this sort of thing.
     
    #3 bisco, Jan 27, 2014
  4. fuzzy1

    fuzzy1 Senior Member

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    With so many variables contributing to both real and apparent MPG, I'd like to know how the OP identified the gas stations as the culprit. I see nothing to indicate how the other suspects were ruled out.
     
    #4 fuzzy1, Jan 27, 2014
  5. wjtracy

    wjtracy Senior Member

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    If you are in a region that requires EPA Reformulated Gasoline, such as NJ or Northern VA, or California, that can possibly be up to 10% less energy (less MPG) ...that would be 3% less for E10 ethanol blend + 7% less possibly due to lower density of the EPA RFG formulation. Gasoline is sold based on octane spec so max MPG is not something you can reliably predict in most cases, but there could be some variation.

    I am not an expert on it, but seems to me smaller independent stations may be less inclined to supply the EPA complex blends and thus possibly have more higher density fuels in their supply chains.
     
    #5 wjtracy, Jan 27, 2014
  6. bisco

    bisco cookie crumbler

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    now i know why we get our best mpg's after filling up in south carolina at a little mom and pop shoppe that hasn't changed since the pumps were first installed.:cool:
     
    #6 bisco, Jan 28, 2014
  7. NewYorkan

    NewYorkan Junior Member

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    No, this is new car from Hezt rental. It had mpg meter. Very accurate. The reading after 3 miles on highway after filling the tank was so acurate. The total miles per tank also confim the mpg. I traveled 2K miles (round trip) in a weekend, only stop for gas.

    Edit: LOL, missed understand you on I95. Yes, it was all highway.
    Also, do you empty the tank completely everytime you filled up? I also put in extra ~40 miles after empty gas light on. Ussually, there are about 2 gal left after the light on, so I drive another gal before I filled up, which is ~1/2 hour after the light was on. My guest is you filled it when you got 1/4 tank left. Most people are nervous, and there is no rest areas on this highway.
     
    #7 NewYorkan, Jan 28, 2014
  8. bisco

    bisco cookie crumbler

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    :p that was a business trip!
     
    #8 bisco, Jan 28, 2014
  9. NewYorkan

    NewYorkan Junior Member

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    Yes, it was business trip. Pick up car on Friday night. Be at Florida Saturday morning. Took care business on Saturday. Left Florida at 7AM Sunday and be home at 9PM. Return the car on Monday. LOL, it's cost $86 (included tax) for the rental. Put 2K miles on the car. They lost on that deal.
     
    #9 NewYorkan, Jan 28, 2014
  10. jhinsc

    jhinsc Senior Member

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    Depending on wind directions and temperature variation, you will see a wide swing in mpgs. I see it all the time in my commute. Some mornings I'm heading into the wind and others I'll have a tail wind and will see a swing of 8-10 mpg.

    I also rented a Focus on my recent trip in OR, and mpg ranged from 28 - 39. While fun to drive, I wouldn't own one. Overall build quality wasn't good and not ideal for back seat passengers.
     
    #10 jhinsc, Jan 28, 2014
  11. fuzzy1

    fuzzy1 Senior Member

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    Miles per tank is a very poor way to measure MPG. I also find MPG meter readings after just 3 miles to be quite unrepresentative of overall consumption.

    Did you use any other methods to compute or verify MPG?
     
    #11 fuzzy1, Jan 28, 2014
  12. NewYorkan

    NewYorkan Junior Member

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    to jhinsc, Wow, 28-39 ranged. On the highway, I never see that different in my whole life. Unless you get stuck on traffic or racing at 120 mph. I don't see more than 3 mpg different.

    To fuzzy1, I did not use the number after 3miles as my calculation. What I meant was that I impressed with the Focus mpg meter. I based my calculation on the full tank of gas about 400 miles trip per tank. For over 20 years of driving, I alway calculate mpg on every gas tank that I filled (that was my hobby, it help me keep track of mpg, it is also tell me if something wrong with my car). I alway reset my trip after filling the tank, and take average mpg by total gal that I filled up. I do not take the reading at 3 min. You got some left over gas in the engine and gas tank. You spend some extra gas to take off from gas station to highway. You cannot depend on any reading for the first mile after you filled the tank.

    Here is how I measured mpg:
    The Focus had 2 display for mpg. One was for realtime mpg. And the other was trip mpg. Both displayed at the same time. Of course, I reset all the meters and trip milage after I filled the tank.
    First gas tank, I started out the trip with full tank from rental (I don't believe it is full). The real time meter showed 37-41 mpg. The trip meter showed 39+ mpg.

    Second tank, the realtime meter showed 33-35 right after leaving the gas station. I didn't know that was the crapy gas at first. Iwas not familiar with the car, so I thought it was my fault. I must did something wrong. After an hour without any improve mpg, I reliazed it was the gas. it stayed around 33-36 for the whole tank. (Night time, not traffic). This tank also showed about 40 miles less compared to the good gas station.

    Luckily, the 3rd tank was the good one. Right after pulling off the gas station, my mpg right back up to 39-41 mpg on the meter. That is why I was so impressed with meter on the Focus. This tank also give more miles. The empty gas light came on much later. Extra 40 miles, that will be 30 min driving is a big different. Also, unlike previous gas tank, the realtime mpg meter never reached 37 mpg for that tank.

    Anyway, I was 2000 miles trip. I can take whole day to tell you the detail how I get the mpg, but you got the point.
     
    #12 NewYorkan, Jan 28, 2014
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