cmolinaro78 Posted May 17, 2010 Report Share Posted May 17, 2010 This evening, I needed to fill up my SGT and the only gas stations around had either 87 89 or 93. Ive only had the SGT a month, and every time have filled up with 91. Now maybe its just in my mind, but after filling up with 93, the car seems somewhat less responsive and powerful. I know the cars are tuned for 91, but I didnt think filling up with 93 would make a difference. Maybe just a bad batch of gas? Link to comment Share on other sites More sharing options...
speedyburd33 Posted May 17, 2010 Report Share Posted May 17, 2010 I've never had a problem with 93 in my SGT. I don't know what to tell you. Link to comment Share on other sites More sharing options...
springer Posted May 17, 2010 Report Share Posted May 17, 2010 I also use 93 octane. Try it again, it shouldn't be a problem. Link to comment Share on other sites More sharing options...
kahmann Posted May 17, 2010 Report Share Posted May 17, 2010 Running a higher octane fuel than what your engine was tuned to run on can definitely result in a loss of performance. 91 to 93 isn't much of a spread though, so I'm surprised you felt any difference at all. Link to comment Share on other sites More sharing options...
LuLu Posted May 17, 2010 Report Share Posted May 17, 2010 93 Octane? Plant your right foot hard into the throttle on any "on-ramp" close to you, and deal wih it... I imagine you will be seeking out 93 octane from now on... Link to comment Share on other sites More sharing options...
kahmann Posted May 17, 2010 Report Share Posted May 17, 2010 93 Octane? Plant your right foot hard into the throttle on any "on-ramp" close to you, and deal wih it... I imagine you will be seeking out 93 octane from now on... Why would he be seeking 93 more often, if his car isn't tuned for it? Higher octane fuel in an engine that isn't tuned for it will yield zero gains and may actually decrease performance. A basic understanding of what an octane rating actually measures is key to understanding why this is the case. Link to comment Share on other sites More sharing options...
bruces Posted May 17, 2010 Report Share Posted May 17, 2010 Ran into that once I put in some Heet the red bottle stuff also has injector cleaner in it, problem cleared up maybe water was in fuel? try it cheap fix if it works. Link to comment Share on other sites More sharing options...
LuLu Posted May 17, 2010 Report Share Posted May 17, 2010 Never in my life have I heard two people explain "octane" and what it really means, the same way. There are too many variables in this scientific game, one being the difference between "octane" and "octane rating", and how both are measured by the fuel industry. Briefly though, "octane" is a measurement of a fuel's resistance to detonation and pre-ignition, aka "anti-knock" to the uninformed public. That said...Stock SGTs come from Shelby tuned for 91 octane fuel. Dumping a load of 87 octane into the tank may show a slight loss of performance, yes, however (and more importantly), a lower octane fuel would put the engine at risk of detonation (and pre-ignition) which will damage the teflon coated hypereutectic aluminum pistons. Once the teflon surface is compromised, the fuel charge will eat away at the base aluminum content (16-18% silicone), and the piston eventually fails. Thus, running lower octane fuel is flirting with disaster. I suppose a custom tune for lower octane is possible, but I would not suggest that. Running higher octane fuel (higher than tuned for) has no such risk. I do not imagine that being tuned for 91 octane and running 93 octane would result in any remarkable performance increase, at least none that could be factually documented. Neither would I expect it to result in any loss of performance, with likewise elusive proof. Moreover, the fresh 93 octane will be diluted by the fuel on board, as well as built up moisture in the storage tanks, thus it is probably closer to 92. My earlier advice to "hit the on-ramp" was meant to remind that the EEC has a storage bank equal to approximately 300 hours of driving (adaptive memory), which it calls upon when driving conditions (such as this octane swap) confuse the EEC's decisions. The sure way to correct this, is to disconnect the battery for 15 min. or more, but this a PITA with radio stations, clock and such. The easiest way is a few second gear WOT passes down the on-ramp, to 6000 RPM. The adaptive memory will take it from there. Link to comment Share on other sites More sharing options...
stormeaston Posted May 17, 2010 Report Share Posted May 17, 2010 Car seems funny hmmmmmmmmmmm..................................................tell that SOB to straighten up and drive right!!!! Just alittle car humor! Link to comment Share on other sites More sharing options...
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