Octane and MPG

Discussion in 'Fiesta ST Chat and Discussion' started by mcummings182, Oct 9, 2013.

  1. WScottCross

    WScottCross Well-Known Member

    That's the ideal speed for milage. Not fast enough for significant wind resistance and you can keep the RPMs quite low. I've only put 220 miles on mine with mixed driving and I'm averaging 28 so far. I have no idea what fuel the dealer put in it, but I bet it was 87.
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  3. mcummings182

    mcummings182 Member

    What's the point of owning an ST if you are gonna drive like a grandma lol
    Last edited: Oct 31, 2013
  4. WScottCross

    WScottCross Well-Known Member

    Yeah, what she said...
  5. CarefreeAZ

    CarefreeAZ Active Member

  6. FiestaST

    FiestaST Active Member

    Aren't you the one complaining the ST is to slow? Lol I'm going to work at a prison I don't think I need to speed on the way there.
    S2r likes this.
  7. mcummings182

    mcummings182 Member

    Yea but I'm not trying to drag race or anything. I just like to get up to speed quickly. I've been starting to skip gears and notice that is definitely helping improve the speed.
  8. pharoh

    pharoh New Member

    Interesting. Do explain. I'm having a hard time agreeing with that unless you're getting massive wheel spin in the gears you're skipping. Not trying to call you out, I just want to hear more on your experiences with that.
  9. mcummings182

    mcummings182 Member

    Maybe I'm just pressing on the gas more and learning how to drive the car better. Idk anything about cars
  10. RodMoe

    RodMoe Well-Known Member

    Define "up to speed"
    If it's the legal limit you only need 3rd at most to get there ... In fact I sometimes forget I have 6th gear !! LoL
  11. eRic

    eRic Active Member

    I'm not sure what it was filled with at the factory [I'm guessing 87 octane] but I have been filling mine with 93 octane and I'm getting 24 mpg so far. my Fiesta ST only has 1200 miles on it so it's a bit early to track fuel economy.
  12. davidp

    davidp Member

    i put 94 in mine .. btw the power ratings are calculated on 93oct fuel .. you lose a lot of torque going down to 87 and mileage is quite bad also.. 80mph highway on cruise i get 50 more miles per tank using 94 vs 87 and it shows even more in city driving
  13. TWDM

    TWDM Member

    FYI the ford mpg estimates were based on 87 octane. What most likely is happening is people floor the pedal more with 87 due to the lack of power compared to 93 and it is affecting the mileage.
  14. S2r

    S2r New Member

    I think the fiesta has the same fuel tank 2011 to current - Grabbed this off the owner.ford.com site on my 2011

    Fuel tank 12.4 gallons (47L)
    2011 Fiesta
    Owners Guide, 3rd Printing

    Edit: which also happens to be the same fuel tank they use in the Focus/Focus ST
  15. johnnyquest

    johnnyquest Member

    My two cents:
    1. If the owner's manual says "premium fuel recommended" then that means it's tuned to run the best with that fuel. The engine makes more power and runs more efficiently with that fuel. Most modern 'performance' cars that are tuned to run on premium will run on regular fuel, however, the ECU will retard the engine timing to prevent detonation, which results in lower power output. They allow for this in the software to allow the owner to run lower octane fuel in the event that higher octane isn't available. In my experience, every 'performance' car I've had that was tuned for 91 octane or higher fuel ran like crap and got terrible gas mileage if I tried to run 87 octane it it.
    2. In most states, premium fuel costs $.20 per gallon more than regular unleaded. The Fiesta has a 12.4 gallon fuel tank, which means it costs $2.48 more per tank to run the fuel the ST was tuned for versus 87 octane fuel. In my case, that's about $10 per month in average driving.

    The good thing is, it's a free country and you can run whatever gas you want in your car. I just alway find it amusing when people spend more money on the 'performance' version of a car and then try to go cheap on the fuel. Can't tell you how many times I've seen/read about this in VW, Volvo, BMW, Fiat, and other car and motorcycle forums. Like I tell my mother-in-law...who always rolls her eyes when I put premium in my Volvo S60 T5, or in my old Jetta GLI VR6...it's about $3.00 a tank to get full power and best fuel economy. But she's one of those folks that will drive 35 miles round trip because she found a gas station on the Internet that sells gas $.05 per gallon cheaper than anyone in town, so...

    Smokin likes this.
  16. TWDM

    TWDM Member

    I would actually have to disagree with your point about efficiency and higher octane. If Ford was able to achieve better mpg with 93 then you would be sure as heck that they'd advertise those numbers.

    No one is disputing the better power, but in terms of mpg 87 is the way to go if you're just driving it like a granny to work.
  17. johnnyquest

    johnnyquest Member

    TWDM, I respect your right to disagree. However, I feel what I stated previously to be correct. From Road and Track:

    "The simplest answer of which fuel to use is to follow automaker advice contained in your car's owners manual. This might be given as a requirement or merely as a recommendation. The latter might be qualified by a statement along the lines of "lower octane may yield reduced performance or inferior mpg."

    The reason for this has nothing to do with energy content. In fact, depending on its blending, a premium fuel may actually contain less energy per unit volume than regular. However, its potential for producing more power and enhanced mpg goes back to MBT and that knock sensor. If premium is recommended, this is the engine's optimal fuel. It'll run on regular—albeit with the sensor invoking ignition timing that's less than that associated with MBT. And with less than Best Torque, there'll be less performance and an mpg hit."

    Read more: http://www.roadandtrack.com/go/news/new-technology/premium-fuel-futures#ixzz2jZK8CFKe
    Smokin likes this.
  18. TWDM

    TWDM Member

    Power and fuel economy are inversely related. It may be more efficient in producing the same power output, but you're getting confused. Fuel economy =/= efficiency.

    Secondly, imagine this scenario: VP of advertising: "Let's advertise 87 octane mpg eventhough it has lower fuel economy than 93! That'll sure get people to buy our vehicles!"

    See how ridiculous that scenario is and now put it in context of your claim.
  19. johnnyquest

    johnnyquest Member

    Not sure why you think that advertised EPA fuel economy numbers are based on 87 octane fuel. From Car and Driver:

    "Measuring fuel economy during the tests is likewise hugely complex, which is why the automakers and the EPA both follow precisely the same protocol. For openers, the chemical composition of fuel varies slightly, so simply retrieving it from a local gas station won’t produce repeatable results. The EPA has a specialized company manufacture small batches of consistent fuel, which is 93 octane (cars running 50-state certifications get a slightly different, 91-octane “California” blend). Before being used, the gas is analyzed to measure its properties, and fuel economy is then calculated based on the measured carbon content of the various tailpipe emissions—unburned hydrocarbons, carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and oxides of nitrogen (NOx)—that are collected in bags made of a special Kynar plastic. A $350,000 gas-analyzing machine then makes minute measurements. The one-percent accuracy of this machine from Japanese company Horiba is amazing considering the minuscule amounts of some of the exhaust constituents—some in quantities as low as a half-dozen parts per million."


    Just to be clear, I fully support your right to run 87 octane fuel and spend your $2.48 per tank any way you choose. However, I stand by my previous posts as well as the articles I quoted to support my original position.

    Smokin likes this.
  20. takuarc

    takuarc Member

    Tested 93 and 95 octanes on a rental corolla and the higher octane definitely makes a difference. I can feel there's more power when going up hill on 95.

    Sent from my GT-N7100 using Tapatalk
  21. Noah

    Noah Member

    I hear that's the fastest car... IN THE WORLD.
    Also where did you get 95 octane?

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