Got 10% better mileage with premium!

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489
Location
Quebec, Canada
My average for the last 4 tanks before premium is 7.7 L/100 Km (mostly Petro-Canada). Last tank using premium (Ultramar)returned 6.87 L/100 Km. A 10.8% gain! I know, I was skeptical too and had never used premium gas in any of my vehicles before (Sonata rated at 9.6 city/6.3 highway and requires regular). I'm impressed as this was not a one day trip to show a "ringer" performance but for commuting to work and general driving around Montreal for 10 days. My commute is 18-22 Km depending on the time of the day. I had some highway thrown in there but also hilly secondary roads ending in a very slow, hilly and rough dirt road before I filled up last night. I use AC anytime it's hot enough because I don't like driving with windows down. The ethanol in regular gas pushed me into giving premium a try and see if I would observe a change. Now, is the gain mostly due to premium gas burning better, more BTU/Liter, octane, better additives, etc. or to the fact that it contains no ethanol and regular contains up to 10%? I'm a careful and mostly smooth driver and have been monitoring my mileage for ever. My little experiment is not a very scientific one, but for me now, if premium is less than 10% more expensive than regular (easy on thursday's at Ultramar), I'll use it and still be ahead. Unless they start to pack it up with ethanol too! Of course, YMMV...
 
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237
Location
Minneapolis
Unless your car needs premium, the gain is probably from not having ethanol in the gas. Anytime ethanol is added to gas, you will take a mileage hit. See if the mileage difference makes up for the higher cost and if it does, go for it. I tried it on a few of my vehicles, and it would end up costing me an additional 3-5 cents per mile to operate the car.
 
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12,385
Location
Northern CA
Better mileage without ethanol is believable. Better mileage with premium if your car calls for premium is believable, particularly with hard driving. 10% better sounds high. How about 4 more tanks with someone else filling your tank and not telling you which one they put in the tank? I was a test engineer for over 2 years and it's really hard to not make tests like that come out the way you think they should when there is human involvement by the tester in the results.
 
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39,804
Location
Great Lakes
Is it possible that summer gas and warmer temps (quicker warmup, less dense air) contributed to this MPG improvement? I always get better mpg during summer (even with A/C on), despite always running on premium.
 
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Minou

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489
Location
Quebec, Canada
 Originally Posted By: XS650
Better mileage without ethanol is believable. Better mileage with premium if your car calls for premium is believable, particularly with hard driving. 10% better sounds high. How about 4 more tanks with someone else filling your tank and not telling you which one they put in the tank? I was a test engineer for over 2 years and it's really hard to not make tests like that come out the way you think they should when there is human involvement by the tester in the results.
Went back with Regular last night. 37 liters in a 67 liter tank so I'm driving with 89 Octane or mid-grade. I should observe a little hit all other conditions being equal...
 

Minou

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Messages
489
Location
Quebec, Canada
 Originally Posted By: Quattro Pete
Is it possible that summer gas and warmer temps (quicker warmup, less dense air) contributed to this MPG improvement? I always get better mpg during summer (even with A/C on), despite always running on premium.
My average for the 4 previous tanks with Regular started in early May so I suspect "summer" gas was used for all tankfuls. As for temperature, it was pretty stable. I use AC when I want and have been parking indoor at home and at work the whole period.
 
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1,841
Location
United We Stand
 Originally Posted By: Minou
 Originally Posted By: TaterandNoodles
Does the 2.4L have an iron block?
Aluminum block and head.
Interesting. I know there have been a number of engines originally listed as aluminum block that are iron. I have 1 in my Rio, the 1.6L alpha was orginally listed as aluminum but its iron. The 2.4L has 10.5 compression even with an aluminum block thats pretty high for regular 87 octane. If you had autotap you could compare the amount of retard that the PCM was seeing with each grade of fuel. I can tell by ear that my 1.6L is not able to retard the timing enough on regular and this year premium 93 octane still has some ping. At some point I am going to have to get it reflashed for less timing. I have found allot of cars locally that have varying degrees of pre-ignition.
 

Minou

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489
Location
Quebec, Canada
 Originally Posted By: TaterandNoodles
 Originally Posted By: Minou
 Originally Posted By: TaterandNoodles
Does the 2.4L have an iron block?
Aluminum block and head.
Interesting. I know there have been a number of engines originally listed as aluminum block that are iron. I have 1 in my Rio, the 1.6L alpha was orginally listed as aluminum but its iron. The 2.4L has 10.5 compression even with an aluminum block thats pretty high for regular 87 octane. If you had autotap you could compare the amount of retard that the PCM was seeing with each grade of fuel. I can tell by ear that my 1.6L is not able to retard the timing enough on regular and this year premium 93 octane still has some ping. At some point I am going to have to get it reflashed for less timing. I have found allot of cars locally that have varying degrees of pre-ignition.
You're correct, my Sonata's compression is 10.5. I've been wondering as well if a Scan Gauge or similar might have been useful in monitoring different parameters with either grade of gas. My GF has a pretty beaten 2002 5 speed Accent with the same iron block as you Rio and it drinks more than my Sonata but I mostly know why...
 
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1,841
Location
United We Stand
I have an 06 with CVVT its a different engine then the 02's. I have a scanguage but it does not measure retard only advance. You could try and compare the advance counts but its very hard to compare with any accuracy. I would suspect your engine is experiencing some form of detonation and that's why it gets better mileage on higher octane fuel. These modern engines are being run as hot as possble (for emissions) which can add to the problem especially with iron blocks. For comparison the acura integra type R used to have 10.6 compression and ran on premium.
 
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9,568
Location
Ontario, Canada
Are you sure you're hearing preignition? I have a hard time believing an engine designed for 87 octane would ever ping using 87 let alone using 93 octane. Do you hold it wide open in 5th gear at 30mph? If you are really worried about it read this article. Autospeed article
 

Minou

Thread starter
Messages
489
Location
Quebec, Canada
 Originally Posted By: TaterandNoodles
I have an 06 with CVVT its a different engine then the 02's. I have a scanguage but it does not measure retard only advance. You could try and compare the advance counts but its very hard to compare with any accuracy. I would suspect your engine is experiencing some form of detonation and that's why it gets better mileage on higher octane fuel. These modern engines are being run as hot as possble (for emissions) which can add to the problem especially with iron blocks. For comparison the acura integra type R used to have 10.6 compression and ran on premium.
Several modern engines with compression ratios above 10 are now spec'ed for Regular. I don't recall ever hearing pinging from my engine and driveability with my cautious driving style has not changed with Premium. I know it's only a tankful but 90% highway tankfuls last summer were returning 7.0 L/100 Km. So to get better than that (6.87 L/100 Km) for 10 days of general driving and commuting is showing an improvement somewhere that should come only from the fuel used.
 
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10,008
Location
Upstate NY
The lack of ethanol is the cause. I've just started filling up with ethanol-free gas again after a long trip using ethanol-laced gas, and am noticing my mileage creeping back up. It's ~1.5 mpg around town, or 10%.
 
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1,841
Location
United We Stand
 Originally Posted By: IndyIan
Are you sure you're hearing preignition? I have a hard time believing an engine designed for 87 octane would ever ping using 87 let alone using 93 octane. Do you hold it wide open in 5th gear at 30mph? If you are really worried about it read this article. Autospeed article
I have a 4 speed automatic so no 30 mph in 5th. Yes I am sure of what I am hearing. If I had a distributor I would just back of the advance. The crank pick up is also not adjustable or I would adjust it. A number of the mazdaspeed3 owners have adjusted the crank pickup. Cooler engine temps would also work. Since I have not found a 170 or 160 degree thermostat I will have to stick with 93 octane. There is an easily noticeable improvement when running 93 octane compared to 87 octane in a parking garage. The difference is very audible without any help.
 
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25,046
Location
ON, Canada eh?
I think you got 10% more mileage because your wallet was significantly lighter due to the cost of the premium fuel! Your vehicle is probably equipped with a Knock sensor that changes the timing based on the octane of your fuel choice, plus you probably have not Ethanol in that mixture only improving your economy more. You need to work out the Cost/KM for regular and premium and see if it's worth the mileage difference! ;\)
 
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1,841
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United We Stand
 Originally Posted By: ravenchris
2007 Sonata, stick. Last week the service manager drove my car and agreed that it pings. He suggested using mid grade gas.
Was that an audible ping?
 
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