Does premium fuel = better MPG?

Discussion in 'Fuel' started by 99BlueBlazer, Apr 10, 2008.

  1. 99BlueBlazer

    99BlueBlazer New Member

    Does premium fuel (which obviously cost more) have any mileage savings compaired to regular unleaded? Other than the "octane" ratings I dont really know what is different between the quality levels of gasoline. :Banane13:
  2. toastblows

    toastblows Well-Known Member

    no, use what owners manual says to use
  3. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Higher octane just has more additives to prevent pre-detonation (aka "pinging"). Because of that it actually has a lower energy density than regular gas (which doesn't have as many additives). For a car rated for regular gas, premium fuel will get you worse mileage (by a little). For a vehicle rated for premium fuel, most will "detune" a bit to accommodate lower octane fuel without "pinging." That can often have a FE hit associated with it.

    In short, if you car does not call for premium fuel, don't use it. You'd just waste your money.
  4. warthog1984

    warthog1984 Well-Known Member

    Quick answer-

    Fuel grades that have different octane ratings are totally different beasts in how they ignite and expand in the engine. The best mileage will be using the fuel YOUR engine is tuned for. Otherwise your just wasting gas.
  5. BailOut

    BailOut My favorite holiday is Earth Day!

    I did my own experiment of 3 tanks each of 89 and 93 octane (my engine is rated for 87). I lost 4% of my MPG on 89 and 9% on 93.
  6. toastblows

    toastblows Well-Known Member

    High compression ratios need higher octane to boost performance. Most cars are 86 octane min, and most min gas stations are 87. 87 will do you just fine. Even 85.5 they make in montana will work, has a nice ping to it :D
  7. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    At higher elevation, you can get away with lower octane without knocking. That's why places like Montana and from personal experience, Flagstaff can get away with selling it.
    Last edited: Jul 10, 2008
  8. Shrek

    Shrek Kaizen Driver

    Try to figure out what your engines compression ratio is. My toyota engine has 10.5:1, and would require high octane if it was not for advanced engine technology.

    So it will run OK on regular, but with high-octane I have a huge boost on below 2000 rpm torque which help me a lot to get high mileage with manual gearbox.

    Low octane fuel burn faster, but that really is only a problem with high-rpm situations. For a hypermiler it is very beneficial to trot along at 1500 rpm and high gear-high load without the engine whasting 50% of the energy because of anti-knock safety kicking in.

    If I fill low-octane fuel I can feel an annoying dip in the moment curve at around 2700 rpm.
  9. diamondlarry

    diamondlarry Super MPG Man/god :D

    I just wanted to add my $.02 worth to everyone else comments and say that premium will only give better FE in an engine that is tuned for it. You will get the best FE with the octane the car was designed for. In older vehicles, the lowest octane you can find that won't cause pinging will get the best FE. I would be curious to see what would happen if I could put 85 octane or less in my Prius.
  10. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    ___Let me add to Larry’s post. The MDX spec’s “Premium Recommended” and unless you are laying into it for the IGN to back off due to the KS, Premium is an absolute waste as regular unleaded will allow her 30 + on the highway at most any time of the year. My experience with regular unleaded in the MDX anyway?

    ___Good Luck

  11. toastblows

    toastblows Well-Known Member

    Run a tank of E85 (higher octane than premium)......let me know how your FE goes :cool:
  12. jcp123

    jcp123 Caliente!

    Well, it depends. In your average 87-friendly car, no. In my SVT, which was designed for 91+ octane, it dropped my mileage about 4mpg to run regular. It pulled a bunch of timing and dumped a lot of extra fuel in the cylinders to keep the 10.2:1 compression from rearing its ugly head - even though I only shifted @ 1700rpm.
    Last edited: Apr 14, 2008
  13. Jimmy

    Jimmy Well-Known Member

    For most cars and most engines, buying anything other than 87 octane is a total waste of money - and does nothing to enhance performance or increase engine durability. Brand name fuels are meaningless as well. Just buy 87 octane, at the cheapest price.

    Why do I feel this way?

    In 50 years of driving I have never used anything but 87 octane, have always purchased it where the price is the lowest, and have never needed an engine overhaul. Right now I am driving a 1995 Buick Roadmaster (purchased new) with 140,000 miles on it. It is equipped with a Corvette V-8 engine, runs like a new one, has never had any engine repairs other than new plugs, and gets 26 mpg on the highway (that's true, believe it or not).

    I also drive a 1988 VW Cabriolet (Rabbit) convertible with a 4 cylinder 90 hp engine. It has over 270,000 miles on it and also uses 87 octane. It is a very peppy, responsive vehicle too.

    Now if I owned a Lamborghini, Ferrari F430, Mercedes-Benz SL, or Porsche - I might have a different attitude.
  14. shifty35

    shifty35 Well-Known Member

    Most high output N/A vehicles and turbo vehicles will require premium fuel. You can seriously damage an engine like that if you run it on normal fuel, especially if it is not knock sensor equipped.

    Even then, knock sensors aren't terribly accurate and a hard run could break your engine pretty quickly.

    For 95% of vehicles, normal octane rated fuel is fine.
  15. toyocam21

    toyocam21 New Member

    theres no way you could do a true experiment unless you were parked in a room...many things contribute to gas mileage...if you did a true experiment your saying you drove the same way for every tank of gas you used, in the same weather conditions, tempurature, electrical components on/off, same traffic, nobody else in the car to add weight, you have to take everything into consideration...if you did all of that then ill beleive...personally i tried to do the experiment and with regular gas driving mostly highway by myself to work and home everyday i get avg 320 miles per tank(approx 16 gal)which would be 20mpg...premium gas i did avg 328(same 16 gal) that would obviously be more than 20 mpg but not enough to calculate...i calculate mpg everytime i get gas and it might be coincidence but premium seems to give better mileage...
  16. Vooch

    Vooch Well-Known Member

    prior engine was a VW VR6 which 'required' 93 - never put a drop into it and it engine ran fine when I sold it at 190,000 miles.

    current engine is a 2.0 turbo with fancy fuel injection also 'requires' 93 - I've tried a few tanks of 93, but did not see any difference in MPG.

    My belief is that Hypermilers are so undemanding of their engines that 87 will do just fine
  17. mongoose

    mongoose Member

    I am interested, is there a different system for rating octane numbers in the states vs Europe?

    it's just that Regular unleaded here is 95 octane, premium is anything from 97 to 99 deppending on the supplier. My Fabia's handbook states that I can run on 91 with a slight performance hit, and in an emergency can run on anything I can get but that I should fill up with 90+ octane as quickly as possible to avoid extra engine wear, but this is all academic since less than 95 just doesn't happen in the UK.
  18. Scandinavian Gigolo

    Scandinavian Gigolo Active Member

    Here's a twist. I noticed the grade breakdown sticker at a Manitoba Shell station that could be summarized as such: Bronze = up to E10; Silver = up to E5; Gold = super premium straight gas.
    Could the octane and fuel economy ruse just be for the benefit of serving/hiding the ethanol ruse?
  19. warthog1984

    warthog1984 Well-Known Member

    Yup. See Here.
  20. pdw

    pdw Well-Known Member

    I agree, .... "below 2000 rpm" .... that's where the best acceleration is located too ... that's where the extra octane is noticeable.
    Last edited: Jul 11, 2008

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