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Gas grade? Gmt 900 2011 5.3

joshw1303

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MaverickZ71 Senior Enthusiast

MaverickZ71

Posted
Posted

My LC9 runs like a slug if I don't run good premium in it and Techron it every 3000 miles. Maybe because the cylinders are sludged up and the plugs fouled from the infamous AFM oil usage problem?

pendragon Enthusiast

pendragon

Posted
Posted

Hi Guys, I'm just trading my 2010 6.2 for a new 2013 6.2, for the 200,000 klms I've done on the 2010 I've used 87 exclusively and get around 15.5 ltr/100 klms (15.1 mpg US) the 6.2 does not have AFM, anyone have any idea whether the economy would improve significantly going to 91+ most of my driving is highway on cruise control

joshw1303 Enthusiast

joshw1303

Posted
  • Author
Posted

Hi Guys, I'm just trading my 2010 6.2 for a new 2013 6.2, for the 200,000 klms I've done on the 2010 I've used 87 exclusively and get around 15.5 ltr/100 klms (15.1 mpg US) the 6.2 does not have AFM, anyone have any idea whether the economy would improve significantly going to 91+ most of my driving is highway on cruise control

 

 

You would see an improvement as the 6.2L recommends Premium fuel.

MikeNH Senior Enthusiast

MikeNH

Posted
Posted
Hi Guys, I'm just trading my 2010 6.2 for a new 2013 6.2, for the 200,000 klms I've done on the 2010 I've used 87 exclusively and get around 15.5 ltr/100 klms (15.1 mpg US) the 6.2 does not have AFM, anyone have any idea whether the economy would improve significantly going to 91+ most of my driving is highway on cruise control

 

It very well might. Best thing to do is to try running premium for a month then see of the results are vastly different. It may be worth waiting a bit until the engine is broken in though.

joshw1303 Enthusiast

joshw1303

Posted
  • Author
Posted

Well that midgrade sure does help, when AFM kicks in does not feel like its going to die. It feels more fluid. Now i just need to hunt down this Techron everyone says to use every oil change.

MaverickZ71 Senior Enthusiast

MaverickZ71

Posted
Posted

Well that midgrade sure does help, when AFM kicks in does not feel like its going to die. It feels more fluid. Now i just need to hunt down this Techron everyone says to use every oil change.

It is Chevron Techron Fuel System cleaner. Available around here at Wal-Mart and the auto supply stores (Advance, O'Reilly's, Autozone, etc.) GM sells it as GM Fuel System cleaner--same stuff.

gnet158 Senior Enthusiast

gnet158

Posted
Posted

I use 87 octane from Chevy with seafoam treaments in-between on all three trucks and never had a problem. I think top tier gas is the way to go, some people swear by AM/PM or costco gas, but not for me.

Daryl LBZ Senior Enthusiast

Daryl LBZ

Posted
Posted

Seems like every time I would get gas at either a Martins or an Exxon the truck would run kind of crappy. Seems to do fine on Sunoco, Hess, and Shell.

TJay74 Senior Enthusiast

TJay74

Posted
Posted

If you watch Orielly's they run the Chevron Techron on sale at times, I only 89 in my truck but for some reason it is a turd as gas mileage. Last trip running 70mph on the highway I only averaged 16.29 (hand calculated). So right now plugs and O2 sensors are on the way in and I will prob see about get a tune from Blackbear once I get some headers lined up.

 

We only have 91 in my market, one store 25 miles away from me sells 93 at the cost of $4.50 per gallon compaired to 91 at $3.60.

NEFisher11 Enthusiast

NEFisher11

Posted
Posted

I am going to try runing 89 for a month and see what happens. Right now i run 87 an average 15.8mpg. Let you know in a month.

jimlem Enthusiast

jimlem

Posted
Posted

Does anyone know if the current GMT900 engines can re-adust themselves automatically on the fly, to changes in fuel octane rating - both switching to higher octane or going back to lower octane, without the need for us to pull fuses to the PCM or disconnect the battery to force the PCM to re-learn and reset to the changed octane?

 

This is a big deal on the Camaro forums. They call it "Pulling fuses numbers 5 and 20." Camaros will recognize low octane gas and reset the timing advance tables to a lesser (read- lower performance) version and then you begin suffering lower performance. But- they cannot reset themselves to make use of high octane without first pulling the fuses to reset the timing tables. To fix this you pull the 2 above numbered fuses (underhood) for an hour or so and fill up with highest octane gas, then next start up, the PCM will begin using the Hi-Perf timing tables.

 

I know Ryan or someone will have a better understanding and info than me so maybe you could translate for us Ryan. If we all want to begin using 89 oct mid range gas, will the PCM recognize it without problems? Or is there a truck equivalent to pulling numbers 5 & 20 fuses to force the reset?

TJay74 Senior Enthusiast

TJay74

Posted
Posted

Jim the Camaro people must not know how the timing map in the ECM works, pulling he fuse does nothing as GM does not use a octane sensor unless the vehicle can run E85. The Camaro is not able to run E85 from the facotry so it does not have a octane sensor.

 

There are 2 timing maps, a high octane map and low octane map. If the ECM sees any spark knock/detonation/KR that exceeds a certain amount of knock over a certain amount of time the ECM will drop into and use the low octane timing map, once a decay time period has passed the ECM automatically goes back up into the high octane table if there is no more knock detected.

 

There is no need to pull fuses, this all happends automatically in the factory calibration.

mymaggiebell Enthusiast

mymaggiebell

Posted
Posted

Well that midgrade sure does help, when AFM kicks in does not feel like its going to die. It feels more fluid. Now i just need to hunt down this Techron everyone says to use every oil change.

techron as montyss says, or even a can of sea foam. i have started putting that in every oil change!!

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