Octane and MPG

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

  1. mcummings182

    mcummings182 Member

    This is probably a stupid question (I don't know a whole lot about cars lol) but does using premium octane give you better gas mileage? The dealership had my car filled with regular and I was only getting about 25 mpg. I filled it with plus on Saturday and I'm getting about 29 mpg now. My next tank is going to be premium so I can see the differences. I know that putting premium in will give the best performance for the car.
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  3. RodMoe

    RodMoe Well-Known Member

    If it works for you who am I to say its not ... Some say yes some say meh... Using the best grade gas the car was designed for is never a bad idea as you wont have to press so hard on the gas to get going as fast as you want.. Now you may become addicted to the punch and start using your right foot even more and smiling a lot more till you get to the pump and find you MPG isn't close to your smiles per gallon LOL
  4. I'm surprised there isn't an MPG thread where people can post how far they go on a tank, driving habits etc. That's a pretty big difference you have seen with 87 vs 89. What were your driving habits when getting 25 MPG? Stupid question here, but does the Fiesta ST have a mileage computer built in? Or are you calculating the MPG manually?
  5. brian

    brian Member

    To the best of my knowledge, using lower octane gas should result in better fuel mileage due to the lower octane fuel burning more easily. Having said that, the bigger variable in fuel mileage will be your driving habits. Smooth, gradual acceleration while keeping the engine out of boost should give you higher mpg's. I also expect that will be rather difficult w a turbo of this size (it's small and starts making boost at lower rpm).

    Also be aware that with winter coming, the gas stations will be switching to winter gas, and your mileage will go down.
  6. brian

    brian Member

    If you are using a onboard trip computer, I'd expect mileage to go up for the first few tanks and stabilize.
  7. kvetcha

    kvetcha Active Member

    Only gone through three tanks so far, but the first one (on 87 from the dealer) was 27.4mpg, mostly city. The second, on 93, was 28.9, mostly city but with one trip out to the country. The third tank, on 93, was 26.4, entirely city.
  8. brian

    brian Member

    I should also add that if you are going to be doing any kind of racing you should be using high test. When I get my ST and make the trip to Deals Gap running over 500 miles of interstate, I'll be using the lowest octane the manual says is safe.
  9. reddog99

    reddog99 Active Member

    The ST isn't the kind of car that encourages mild driving habits. My average MPG has dropped 10 mpg from my 2011 Fiesta. :joyful:
  10. Bluto

    Bluto Member

    From what I've read on many cars it is a wash, if the engine is designed to run super using it will give slightly higher mileage at a slightly higher cost. Since it is only $0.20 more per gallon where I live (about 5%) I'm planning to run super all the time. If you drove 10K miles per year at 25 MPG you would burn 400 gals. of gas and super would only cost about $80 more for the year even if there were no mileage advantage. Focus ST drivers might have a better idea on all this since their cars have been on the road longer.
  11. mcummings182

    mcummings182 Member

    My driving habits are pretty normal, I don't push the car to the max or anything. I am kinda new to driving stick though, so that might be why it's slightly improving over time as I get more used to it. My friend taught me how to drive stick for a couple months before I got this car. I am looking at the mileage it displays on the dashboard.
  12. speedprotege

    speedprotege Member

    I will be getting my car next week and on the 26 I'm going to tail of the dragon than myrtle beach
    Will be driving about 3000 total miles will be switching from 87 91 93 to do some testing
  13. The link is on my Kindle HD so I don't have access, but one website stated the MPG ratings for the Fiesta ST are supposedly on 87 octane. HP and torque on 93. Fueleconomy.gov says 87 octane as well. However Ford site says 93. Quite confusing. I tend to believe brian and his theory. Would like to find out 100% sure though. Will post links when I get my Kindle back.

    In the mean time, does the Fiesta ST have an on board MPG calculator? And how many miles is everyone getting per tankful? I know driving habits contribute tons, but just curious.
  14. Removed

    Removed Guest

    There is one, you toggle to it with the button on the left stalk. I'm averaging 25.5mpg but that is with ~95% city/surface street driving.
  15. kvetcha

    kvetcha Active Member

    I'm averaging 27.6 with 95% city as well, including plenty of DC commutes.
  16. BRGT350

    BRGT350 Well-Known Member Staff Member

    It took about 1000-1500 miles in the ST for the MPG to go up. It stays pretty consistant until about 9000 miles, and then it starts to drop off. As it gets close to oil change time, the MPG begins to go down quickly. My 2011 does the same thing, so I start doing oil changes around 8000 miles or less. I run 93 only in the ST and 87 in my 2011. The ST will run on 87, but performance suffers.

    On a side note, I actually get better MPG out of the ST than I do out of the ST. The reason? It produces plenty of mid range power so I don't have to drive it like I hate it in order to get it to go.
  17. pharoh

    pharoh New Member

    I guess you missed my thread then: http://fiestast.net/threads/fiesta-st-real-world-mpg.211/
  18. Mayhem

    Mayhem Active Member

    I am curious what "93" equates to compared with gas locally...
    We get 87/91/94

    Also curious.... if it's worth going from 91 to 94... Or if it will run 94? Or if we are supposed to stick between 91 or 87 here.

    Edit ** scrolling up... Looks like those mentioning 93, also get 91 and 87... So maybe 93 is the same as 94 here?
  19. kvetcha

    kvetcha Active Member

    93 and 94 are very close. Should be totally fine.
  20. Bluto

    Bluto Member

    FWIW octane is calculated by various methods around the world but it looks like the US and Canada are the same per Wikipedia...

  21. mcummings182

    mcummings182 Member

    Is the size of the ST gas tank smaller than the other Fiestas? Because I noticed that when I had my 2011, I would fill it up and it would give me almost 500 miles til E. When I fill the ST up, it gives me almost 400 miles.

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