G5 Club banner

1 - 20 of 67 Posts

·
Registered
Joined
·
649 Posts
Discussion Starter #1
When reading the user manual (Which I recommend you browse through to learn more about your vehicle) you will read all about the gas that should be used in cars with this motor - specifically the GT.

GM manual recommends 91 Octane or higher. Low and Mid grade fuels can be used, HOWEVER; you will not be maximizing the efficiency of your engine and you will find that the power created while using lower grade fuel is much less then when using a high octane fuel. Also to be noted, while using lower grade fuels you may hear a slight knocking/ticking noise in the engine. It will not hurt the motor to run a lower grade of fuel - but why own a GT if you aren't using it to its full potential? The GT has a 32-bit PCM which advances the timing to take advantage of the combustion of the higher grade fuels.
2.2L motors will not notice a difference while using a higher octane fuel.

Also, on a side note. GM recommends to NEVER use fuel additives.
 

·
Super Moderator
Joined
·
1,939 Posts
I can atest to this, with real-world experience. I put some 89 octane in, didn't wanna spring for the high premium, no 91 option. Day or two later, low RPMs, up hill on the highway, good load on the engine, and I hear knocking. Couldn't place the noise at first, but eventually figured it was knocking. A tank or two of 91 later, and the 89 is worked out. Next tank was 93, and my fuel economy went up a few points. Yeah, 91 is the minimal. If there isn't a 91 option, go higher, not lower.
 

·
Registered
Joined
·
232 Posts
^^ X 2 to that! I recomend V-Power from Shell. Got all the cleaners and shit in her too. I hear the Ecotecs don't like any Ethanol blended fuel, so if you're around Mohawks or Huskys, don't use their gas.
 

·
Registered
Joined
·
2,128 Posts
the manual says not to use fuel with ethanol. Dart Baron has more of a selection for fuel grade than I do around here...pretty odd, but all is see around here is 88,89, and 93 octane. On my 2.2, I usually use 89 octane and 93 whenever I can.
 

·
Registered
Joined
·
162 Posts
farfrmnormal said:
^^ This is what I read off a consumer website - 32-bit ECU's are programmed MUCH different then the average.
They're talking about the method used to program them. The type of fuel has nothing to do with the type of ECU but the characteristics of the engine and the programming of the ECU.

For example the G6 and most new GM's (including the G5) use the same type of ECU, however they don't all share the same programming for obvious reason, the recommendation for the 3900 is 87 octane.
 

·
Resident Troll
Joined
·
5,921 Posts
im not sure of the compression difference between the 2.2 and 2.4 if there is any, but usually a higher compression requires a higher octane fuel.
 

·
Registered
Joined
·
162 Posts
karnivor said:
im not sure of the compression difference between the 2.2 and 2.4 if there is any, but usually a higher compression requires a higher octane fuel.
Higher compression can be tuned to run lower octain fuel, but thats a huge part of it.
 

·
Registered
Joined
·
50 Posts
As for the 2.2L, you should definitely not use any higher than 87 (like it states in the manual). The higher octane will actually hurt performance rather than giving you more power. The timing curves set in the ECM for those motors are programmed for that specific octane. Using a higher octane makes it harder for the flame front to begin when it should. In another words, you're losing some timing advance (higher octane takes more time to fully ignite). And the 2.4L should be at least 91. I'll be the first to admit that I was guilty of using 89 octane, but after doing some research on this, it doesn't really benefit the motor. However, definitely use a good quality fuel. Don't put some lesser-known brand of fuel in the tank because it was a bit cheaper. Once again, there was a big debate, and it's probably still going on, on cobalt forums. Just my two cents. :idea:
 

·
Registered
Joined
·
162 Posts
mikeyboy0382 said:
As for the 2.2L, you should definitely not use any higher than 87 (like it states in the manual). The higher octane will actually hurt performance rather than giving you more power. The timing curves set in the ECM for those motors are programmed for that specific octane. Using a higher octane makes it harder for the flame front to begin when it should. In another words, you're losing some timing advance (higher octane takes more time to fully ignite). And the 2.4L should be at least 91. I'll be the first to admit that I was guilty of using 89 octane, but after doing some research on this, it doesn't really benefit the motor. However, definitely use a good quality fuel. Don't put some lesser-known brand of fuel in the tank because it was a bit cheaper. Once again, there was a big debate, and it's probably still going on, on cobalt forums. Just my two cents. :idea:
Basically what he's trying to say is octane slows down the burn, running the lowest octane possible without knock is what you want to do.
 

·
Registered
Joined
·
97 Posts
blackriderg6 said:
farfrmnormal said:
^^ This is what I read off a consumer website - 32-bit ECU's are programmed MUCH different then the average.
They're talking about the method used to program them. The type of fuel has nothing to do with the type of ECU but the characteristics of the engine and the programming of the ECU.

For example the G6 and most new GM's (including the G5) use the same type of ECU, however they don't all share the same programming for obvious reason, the recommendation for the 3900 is 87 octane.
Even the base G6 2.4 has the 32bit PCM but it's not programmed to advance timing to use 91 octane gas.
 

·
PSD=PostSaturnDepression
Joined
·
826 Posts
I would also think that because they are maximizing the output of a little 4 banger, they tune it to run with 91 octane, plus the VVT takes advantage of this added umph from the gas which would explain why you see a small increase in fuel economy when running it after a while.
 

·
Registered
Joined
·
328 Posts
I use fuel with up to 10% ethanol and have had no problems. I have put over 7000km on my car in the last 2 months and not a single issue with this fuel.
 

·
Super Moderator
Joined
·
1,939 Posts
Probaably not. I have noticed a slight decrease in performance when using 'dry gas', the proper stuff. Could be the disolved water, or the isopropyl itself. It would be nice to hear from a real, in-the-know tech on how different alcohols react in the Ecotec.
 

·
Registered
Joined
·
277 Posts
PursuitGT said:
What the manual says is not to use E85 gas
Ah... that makes more sense... actually... more like it almost goes without saying.

I did recall seeing in there that we should NEVER EVER... ;-) use fuel with methanol.

I wonder if nitromethane would be ok? :twisted:
 

·
Registered
Joined
·
277 Posts
DartBaron said:
Probaably not. I have noticed a slight decrease in performance when using 'dry gas', the proper stuff. Could be the disolved water, or the isopropyl itself. It would be nice to hear from a real, in-the-know tech on how different alcohols react in the Ecotec.
Interestingly enough, Ethanol is higher octane... as it burns slower... but... it does not contain as much energy as gasoline. So yeah... the higher percentage of ethanol, the less energy per gallon / litre of fuel.

Hence.... the more ethanol, the lower the fuel economy. In theory at least...
 
1 - 20 of 67 Posts
Top