Page 1 of 4 123 ... LastLast
Results 1 to 10 of 33

Thread: Fuel efficiency: Unexpected differences (comparing each half of a round trip)

  1. #1
    Senior Member
    Join Date
    Apr 2018
    Location
    Atlanta Metro
    Country
    United States
    Posts
    3,527
    Thanks
    37
    Thanked 1,393 Times in 1,010 Posts

    Fuel efficiency: Unexpected differences (comparing each half of a round trip)

    Guys (and gals?),

    I just returned from my dad's house. I found a decent use for the A Avg/mpg. I usually fuel up before I leave to his house (140 miles one way) and do my fuel mileage. But this time, I thought I would use the A Avg/mpg since I had just refueled shortly before this trip.

    Let me preface by saying this is not a complaint thread. It's all good. Very satisfied will the mpg so far. Far better than the EPA numbers.

    So, as a general rule, I tend to always get slightly better mpg going north (from Atlanta south-side to almost Chattanooga), than I do returning home. Not sure why, but that is definitely the trend, even though I generally always run the same speeds. And since buying my Honda Rebel, my "official rated" mpg speed rating is at 72 mph. Why? Because my Honda Rebel 250 will only top out at 72 mph on flat level ground. Speedo says 75, GPS says 72. And on the interstate I just hold the Rebel WAO. It doesn't have enough power to hurt itself. And it will get about 56 mpg at WOT. So, 72 is my "qualification speed" just out of respect to my Rebel.

    So, when I went to go to my dad's house Friday evening, I manually reset A Avg/mpg before cranking to leave my driveway. I drove up there and when I parked in his driveway it read 44.0 mpg. Not bad. That's probably ~42 mpg. I didn't have to reset the A Avg/mpg when returning home Sunday afternoon, it did it itself automatically. It read 48.8 mpg once parked in my own driveway. That's ~46.5 mpg.

    Excellent mpg. But what I don't get is the huge disparity. That's a 6.8 mpg difference. Both times doing 72 mph. And usually it's better going north by about 0.5 mpg. So, it is very strange. Maybe I had a slight tailwind on the way home. It didn't feel like it. And on the whole 125 miles of interstate cruising, coming south, I canceled the cruise twice (besides to take my final exit). 72 mph the whole way through Atlanta. I find it fun to try to wade my way through traffic and not have to cancel the cruise, or use my foot to speed up. One cancel was merging from 75 south onto I-285. There's a really sharp curve that wouldn't be the best idea to attempt it in the Mirage at 72 mph. The other was just a traffic related cancel.

    Anyway - I wanted to see if you guys figured it must have been a wind direction issue as well. Or ... something else? I had maybe 35 miles on that tank before the trip, and rode around in his town a couple times running errands for him. Now I'm back home and the whole fuel gauge area is flashing at me. Will refuel at lunch and report back.


    Last edited by MetroMPG; 12-18-2020 at 03:21 PM. Reason: (added info to title)

        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


  2. #2
    Moderator Eggman's Avatar
    Join Date
    Sep 2015
    Location
    Cleveland, Ohio
    Country
    United States
    Posts
    10,156
    Thanks
    4,039
    Thanked 2,788 Times in 2,107 Posts
    Factors that have an influence on fuel consumption in my experience:
    1. Wind resistance (try leaving early & slowing down to see the real magic happen.) Was it breezy? A big cold front swept through Ohio, maybe it hit there? You know your weather conditions.
    2. Temperature - inverse relationship of temperature to fuel consumption.
    3. Tire pressure - similar to temperature, but you don’t mention changing yours.

    Yours are good numbers. Sounds like headwind but I wasn’t there haha.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


  3. The Following User Says Thank You to Eggman For This Useful Post:

    MetroMPG (11-03-2020)

  4. #3
    Senior Member
    Join Date
    Apr 2018
    Location
    Atlanta Metro
    Country
    United States
    Posts
    3,527
    Thanks
    37
    Thanked 1,393 Times in 1,010 Posts
    Quote Originally Posted by Eggman View Post
    Yours are good numbers. Sounds like headwind but I wasn’t there haha.
    I have been fighting / repairing my Burgman 650 for a couple months. As of Thursday night, it is finally roadworthy again. I finished working on it Thursday night, but had other stuff to do. It was nice and warm when I finished. When I came out again near bedtime to carry trash to the garbage can, it was very cold. And has steadily been getting colder for the next following days. With nice clear skies. Usually that means a high pressure front pushed through with trailing cool air.

    It was really cold again this morning. Maybe I had a touch of headwind going north Friday, and a touch of tailwind yesterday afternoon coming home (leading to it being nearly freezing this morning). That must be the cause.

    I'm going to treat this car nominally and let it do what it do. Meaning: I'm not going to do anything to it that might be deemed detrimental in the long run. I'm going to do regular maintenance, keep the tires rotated, balanced and pressurized nominally. Drive it my normal conservative way, and let it achieve the mpg it can achieve. Because, it achieves fantastic mpg as it is. I don't want to compromise driving satisfaction just for a couple more mpg, when the mpg is great as it is.

        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


  5. #4
    Senior Member Dark Magenta's Avatar
    Join Date
    Jan 2019
    Location
    Minneapolis, MN
    Country
    United States
    Posts
    195
    Thanks
    29
    Thanked 55 Times in 48 Posts
    Quote Originally Posted by Eggman View Post
    Factors that have an influence on fuel consumption in my experience:
    1. Wind resistance (try leaving early & slowing down to see the real magic happen.) Was it breezy? A big cold front swept through Ohio, maybe it hit there? You know your weather conditions.
    2. Temperature - inverse relationship of temperature to fuel consumption.
    3. Tire pressure - similar to temperature, but you don’t mention changing yours.

    Yours are good numbers. Sounds like headwind but I wasn’t there haha.
    4. I live near the Mississippi River, and suspect that some of my drive's MPGs have a lot to do with going uphill more than downhill, or vise versa.

  6. #5
    Moderator Eggman's Avatar
    Join Date
    Sep 2015
    Location
    Cleveland, Ohio
    Country
    United States
    Posts
    10,156
    Thanks
    4,039
    Thanked 2,788 Times in 2,107 Posts
    Quote Originally Posted by Dark Magenta View Post
    4. I live near the Mississippi River, and suspect that some of my drive's MPGs have a lot to do with going uphill more than downhill, or vise versa.
    It’s funny that on some hilly drives my MPGs improved. Maybe due to lots of coasting?

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


  7. #6
    Senior Member
    Join Date
    Apr 2018
    Location
    Atlanta Metro
    Country
    United States
    Posts
    3,527
    Thanks
    37
    Thanked 1,393 Times in 1,010 Posts
    I just refueled. Lower than I expected. I've broken down the numbers, just for fun.

    I'm assuming the Avg mpg numbers are 3 mpg optimistic as indicated on the the display.

    354 miles on the tank.
    280 miles of that on the interstate @ 72 mph.
    74 miles "around town."

    I used 8.507 gallons over 354 miles, which equals 41.613 mpg for the tank.

    44.0 mpg going north (displayed) = 41 mpg
    48.8 mpg going south (displayed) = 45.8 mpg
    (Just for grins, that's 43.4 mpg at 72 mpg ... not bad).
    Doing math, that means my "around town" mpg = 34.9 mpg.

    That tends to make sense.

        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


  8. #7
    Still Plays With Cars Loren's Avatar
    Join Date
    May 2018
    Location
    Florida
    Country
    United States
    Posts
    1,225
    Thanks
    324
    Thanked 936 Times in 539 Posts
    Quote Originally Posted by 7milesout View Post
    So, when I went to go to my dad's house Friday evening, I manually reset A Avg/mpg before cranking to leave my driveway. I drove up there and when I parked in his driveway it read 44.0 mpg. Not bad. That's probably ~42 mpg. I didn't have to reset the A Avg/mpg when returning home Sunday afternoon, it did it itself automatically. It read 48.8 mpg once parked in my own driveway. That's ~46.5 mpg.

    Excellent mpg. But what I don't get is the huge disparity. That's a 6.8 mpg difference.
    I'm trying to figure out where you get 6.8 mpg difference from the numbers supplied.

    If you take the numbers direct from the display, it's 44.0 and 48.8... that's a 4.8 mpg difference.

    If you take your corrected numbers, that's 42 and 46.5... a 4.5 mpg difference.

    Let's look at this a different way. Average your two trips using your adjusted numbers. 42 + 46.5 / 2 = 44.25.

    44.25 is your average.

    46.5 is your high.

    44.0 is your low.

    You're +/- 5%. It's really not that much. It's just that when the numbers get over 40 mpg... the difference just seems like a lot.

    If you were talking about a car that got 24 mpg average. A range of +/- 5% would only be 1.2 mpg in either direction. You'd be talking about 22.8 to 25.2, which doesn't seem like as much, right?

    The Mirage will never be as consistent as a vehicle where you're at constant WOT all the time, though. Unless you drove it in 3rd gear at WOT at whatever speed that generates. Then, the MPG wouldn't be as good, and you'd be constantly bouncing off of the rev limiter... but, it would probably be more consistent!

    Another potential factor in your drive is traffic. Friday evening, there was probably more traffic. And if you're a good driver, when there's traffic ahead, you let off the gas early and coasted towards it. The Mirage is GREAT for that kind of thing. That's where it shines. The more you coast, the better your MPG as long as you don't "floor it" to get back up to speed.

    Sunday... probably less traffic. More consistent cruising speed. Less coasting.
    Simplify and add lightness.

  9. The Following 2 Users Say Thank You to Loren For This Useful Post:

    MetroMPG (11-03-2020),Top_Fuel (11-02-2020)

  10. #8
    Senior Member
    Join Date
    Apr 2018
    Location
    Atlanta Metro
    Country
    United States
    Posts
    3,527
    Thanks
    37
    Thanked 1,393 Times in 1,010 Posts
    Yeah, you're right. I typo'd the difference in 48.8 and 44.0. 4.8 mpg difference, not 6.8. That's not bad. The corrected would be 45.8 - 41.0, which is still 4.8 mpg difference of course.

    Because Atlanta traffic is so horrible, I usually come home, do a few things around the house and leave about 7 pm. I left about 7:30 pm this time to head north and through the horrific traffic horde. The traffic was still much worse than when I came back. So that would factor in as well. I coast like hell as much as I can. I try to press the cancel early enough that I never have to touch the brake pedal to account for traffic ahead that I cannot ease on around.

    I'm tickled with the mpg. But regardless, I will always shoot to improve it, just not willing to spend any significant gas money on very tiny or unsubstantiated mpg improvements. I'll take what the Mirage can deliver as it stands ... it is outstanding.

        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


  11. #9
    My fuel economy on my way to work is way better than on my way home, according to the car. I can usually get under 5l/100km(47mpg) by the time I get to work. It showed as low as 4.3l/100(54mpg) once or twice. I leave before 6am,very little traffic and can sometimes time make it through the street lights without having to stop.

    My way home, different story, usually the display shows around 6l/100k(39mpg) but can get down to 5.4ish(43mpg). My route home usually has stop and go traffic on a freeway that's had construction blocking 2 lanes of traffic for the last 2 years with no sign of when it'll end. Kinda like the flu...
    Biggest factors I have are traffic, construction and I drive faster when I'm heading home. Beer doesn't drink it self.

    My favorite part of the car is you get great fuel economy no matter how you drive. 40mpg is pretty decent. I struggled to get 30mpg in the wifes 2015 optima, had to drive the speed limit and go easy on the throttle everywhere...
    Mirage videos:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  12. #10
    Moderator Eggman's Avatar
    Join Date
    Sep 2015
    Location
    Cleveland, Ohio
    Country
    United States
    Posts
    10,156
    Thanks
    4,039
    Thanked 2,788 Times in 2,107 Posts
    Hey 7milesout let’s revisit this in 3-5,000 miles after break-in.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •