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New 2011 Silverado in March....About ready to off-load it

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by 94blackcamaroz28, Jul 27, 2011.

  1. stchman

    stchman New Member 1000 Posts

    I know this thread is somewhat old, but I've had 2 Silverados, both with 5.3 and AFM and have LOVED them both.

    IMO, turning off the AFM is kind of a dumb idea and will hit your gas mileage, but it is a choice.
  2. the phantom

    the phantom Active Member 1000 Posts

    @Kapelusprime hit the nail on the head with some of his thoughts on this. I notice when my AFM kicks in but it is no way annoying. I also noticed that around 6k miles the transmission began shifting a lot less. So I do believe the transmission does "learn" driving style. I originally thought this was BS when I was told it but I now know it to be fact. I will also suggest that the fuel octane does make a difference in how "seamless" the AFM is. I put 87 octane in at one point and did notice the "jerking" that some here speak of. I now put in 93 octane and have noticed no more jerking and have actually gained almost a full 1 mpg. So at 13 cents more a gallon at approximately 25 gallons is $3.25 more per fill up, the math is a no brainer for me to stick with the 93 octane.
  3. stchman

    stchman New Member 1000 Posts

    I don't know where you live, but here in St. Louis, premium unleaded in ~$0.30 a gallon more. So for me, I would have to spend ~$7.50 a tank more.
  4. j cat

    j cat Active Member 1000 Posts

    where I live 87 is 3.50 /gal and the 93 is 3.70 / gallon. its 2o cents more per gallon. some up to 25 cents.

    with 93 octane you will see a higher MPG with E85 a much lower MPG ..

    its all about BTU / gallon.. more btu more cost... diesel has the most BTU so you get the best MPG. it also is the most expensive.

    I can see where 93 octane would reduce the engine lag when changing into the low / high power state of operation.
  5. the phantom

    the phantom Active Member 1000 Posts

    Yeah I apologize I was comparing 87 octane to 91 octane. Here in NY it is .13 difference and the 93 octane is .22 higher than 87. But even still at even $5-$7 dollars difference a tank with an increase of 1 mpg at 25 gallons is 25 miles more a tank and im getting 13 miles to the gallon the math still tells me to buy the premium grade.
  6. j cat

    j cat Active Member 1000 Posts

    If your paying .13cents more for 91 octane then using that would be a better way to go. today I happen to notice a mobil gas station 3.65 87 octane 93 octane 3.99 ..........

    I get 19 mpg on the hyway in summer 15 mpg around town. 373 gears..1500 5.3L .
  7. stchman

    stchman New Member 1000 Posts

    Gasoline engines that are designed to burn regular unleaded gasoline(87) will not get better fuel economy by putting premium unleaded(93) into the tank.

    Octane is a combustion inhibitor, not an MPG increaser.

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