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

**stchman** · 11-26-2012, 12:31 PM

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.

**the phantom** · 11-26-2012, 01:39 PM

@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.

**stchman** · 11-26-2012, 02:54 PM

Originally Posted by the phantom

@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.

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.

**j cat** · 11-26-2012, 06:19 PM

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.

**the phantom** · 11-26-2012, 06:35 PM

Originally Posted by stchman

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.

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.

**j cat** · 11-27-2012, 05:14 PM

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 .

**stchman** · 11-27-2012, 11:57 PM

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.