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Regular vs Premium Gas


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Just purchased the new 2017 Reserve AWD MKZ and love the car but the manual tells me it runs on 87 octane gas but in order to get the full horsepower on other sites it says to use Premium Gas.  Back in the day, I read something that stated unless it says run the car off of premium gas in the manual its is a waste of money.  What say you forum :)

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Mods pls delete I posted in the wrong section

No need to delete.  I'm moving the post to another forum.

 

WRT your question, first which engine do you have?  The Turbo engines will run just fine on regular but will not develop their full rated hp.  You may see worse MPG on regular, as the ECU will pull timing on the lower octane fuel.  The 2.0 develops 231hp on regular vs. 240 on 93 octane.  IDK the exact figures for 3.0 AWD but IIRC, it loses at least 20 hp on regular.  I can feel the difference in mine.

 

What applied "back in the day" no longer does as smaller, turbocharged engines proliferate.

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  • 1 year later...

Just for fun I filled with mid-grade 89 to see if there would be any difference from 87.  I feel no performance difference however have noticed that so far about half way though the tank and I am getting 1mpg less.  Not exactly scientific of course but so far I notice no gain in spending the extra $4 or $5 per tank for the slightly higher octane #

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  • 2 months later...

little late to the party but it will take several tanks for the computer to compensate for the fuel unless you use forscan to reset what it has learned.  The car will pull timing to prevent detonation.  Anytime it detects Detonation it will pull timing and it probably won't add it back once it pull it.  I noticed a hell of a difference from the 87 octane the dealer filled it up with and then the 91 pure gas after resetting the computer.  She only gets premium and only Shell or BP.

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8 hours ago, FunktasticLucky said:

little late to the party but it will take several tanks for the computer to compensate for the fuel unless you use forscan to reset what it has learned.  The car will pull timing to prevent detonation.  Anytime it detects Detonation it will pull timing and it probably won't add it back once it pull it.  I noticed a hell of a difference from the 87 octane the dealer filled it up with and then the 91 pure gas after resetting the computer.  She only gets premium and only Shell or BP.

You are "Lucky" if you can get 100% gasoline.  Where I live, E10 is mandatory.

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18 minutes ago, drolds1 said:

You are "Lucky" if you can get 100% gasoline.  Where I live, E10 is mandatory.

For the longest time it was mandatory premium he 100 percent gas but it was only 91 octane. They have since started moving away from it so we are getting more and more 91 w/ ethanol. Shell and BP still have pure gas in their premium grades though.

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10 hours ago, FunktasticLucky said:

little late to the party but it will take several tanks for the computer to compensate for the fuel unless you use forscan to reset what it has learned.  The car will pull timing to prevent detonation.  Anytime it detects Detonation it will pull timing and it probably won't add it back once it pull it.  I noticed a hell of a difference from the 87 octane the dealer filled it up with and then the 91 pure gas after resetting the computer.  She only gets premium and only Shell or BP.

How do you reset the computer? Unhook the battery?

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On 11/27/2018 at 3:11 PM, MKZMark said:

How do you reset the computer? Unhook the battery?

Takes longer than if you use a OBDII reader like OBD MX and FORScan (free software). We're lucky to have that software which is why I sorta stick to Ford and Lincoln for daily drivers.

Under the PCM it's called Learned Octane Ratio. Goal is to have it at 100% for minimum timing pull. FORScan will reset it to 0% when you choose to reset adaptive learning under the PCM.

If you do find true pure gasoline, you'll experience better fuel economy. However ethanol actually allows a engine to work harder since ethanol is harder to burn (and consumes more which is why fuel economy becomes worse). This is why some like to get higher ethanol concentrated fuels like E30 and E89 if fueling systems allow it (the 3.0 MKZ can do this).

Corn makes more power, but real  gasoline allows for better fuel economy.

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