octane

[hudson773]

after watching the Engine Masters show on octane where they compared regular with 93, 110, 120 and e85 on the dyno and found NO significant power difference, are you still willing to pony up .20 a gallon more for premium and much more for the racing stuff? all the fuels liked the same timing advance which kind of debunks the theory that higher octane burns slower.. watch the episode if you can, it was very interesting.

[Bigdumogre]

There are plenty of people making more power on 93 and e85 with dyno results to prove it. Did they tune the car for each one ?

[0stones0]

Originally Posted by hudson773

after watching the Engine Masters show on octane where they compared regular with 93, 110, 120 and e85 on the dyno and found NO significant power difference, are you still willing to pony up .20 a gallon more for premium and much more for the racing stuff? all the fuels liked the same timing advance which kind of debunks the theory that higher octane burns slower.. watch the episode if you can, it was very interesting.

Where are you getting this number from? Much closer to .80 around here.

[gtstorey]

Power based upon octane is really dependent on whether your compression and cylinder design needs it.

[Moto-Mojo]

Probably a dime difference here. And if I were a daily commuter, $1.60 per fill up would add up. The car’s tuned for 91 and it’s not a DD so not a huge deal to me.

[redcoats1976]

i have an LFX.ive run 87,89,and 93 in it,6 months on each one.never noticed any difference in power or driveability.now that gas is expensive itll be 87 this summer unless i start noticing problems.central florida is always over 90 degrees and 90% humidity.

[NOT A 45]

Unless called out by a label on the fuel door saying "premium fuel required" or "premium fuel recommended" [U]All[U]GM vehicles are designed to run on regular 87 octane fuel. I have run both 87 and 93 in my 13 SS with no discernable difference. Once you've modified these vehicles your talking a new ball game.

Recommended Fuel
If the vehicle has the 3.6L V6 engine (VIN Code 3), use regular unleaded gasoline with a posted octane rating of 87 or higher. If the octane rating is less than 87, an audible knocking noise, commonly referred to as spark knock, might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service.

If the vehicle has the 6.2L V8 engine (VIN Code W) or the 6.2L V8 engine (VIN Code J), use premium unleaded gasoline with a posted octane rating of 91 or higher. For best performance, use premium unleaded gasoline with a posted octane rating of 93. You can also use regular unleaded gasoline rated at 87 octane or higher, but the vehicle's acceleration could be slightly reduced, and a slight audible knocking noise, commonly referred to as spark knock, might be heard. If the octane rating is less than 87, a heavy knocking noise might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. Otherwise, you could damage the engine. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service.

Required Fuel (ZL1 Only)

If the vehicle has the 6.2L V8 engine (VIN Code P), use premium unleaded gasoline with a posted octane rating of 91 or higher. For best performance, use premium unleaded gasoline with a posted octane rating of 93. You can also use regular unleaded gasoline rated at 87 octane or higher, but the vehicle's acceleration could be slightly reduced, and a slight audible knocking noise, commonly referred to as spark knock, might be heard. If the octane rating is less than 87, a heavy knocking noise might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. Otherwise, you could damage the engine. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service.

[hudson773]

Originally Posted by Bigdumogre

There are plenty of people making more power on 93 and e85 with dyno results to prove it. Did they tune the car for each one ?

they retuned each time to get correct timing and A/F ratio. numbers matched across the board. all liked 22' (I think) timing, so octane didn't make a slower burn. they were very thorough with each test. find it and watch it. the final conclusion was if your car doesn't knock on regular, and most all modern cars today won't, more octane/cost gets you practically nothing. BIG cost diff

[Royal Tiger]

I have back to back Dyno pulls to show I made almost 60 more rwhp just going from 93 to e60. Maybe in a stock car it doesn’t matter, although I know Car & Driver did a test and one was a Corvette that had higher HP and MPG on 93 than 87.

And by the way E50-81 is currently $1.51 cheaper a gallon than 93 at the station I go to so I’m getting more power (but less mpg) for less money.

[FasNuf]

I thought that episode was comparing what spark to reach MBT. Either way, it was a strange episode

[InFiD3ViL]

Our cars have a high and low octane table in the stock tune. That low octane table has drastically reduced timing compared to the high table.
If you run 87 on an SS, you are dropping to the low octane table, thus losing peak HP and likely HP throughout the rpm range due to timing retard. But there is definitely room for confusion here...

For instance, running 93 in a car tuned and designed for 87 is not going to net you any additional horsepower (with zero tune/part changes made). At the same time, running 87 in a car designed for 93 can and likely will result in a net HP loss on our modern computer controlled cars, and in some cases can be dangerous.

If I run 87 in my SS I am likely going to break something since my tuner combined the high/low octane tables. Therefore I must run 93 at all times. Not all tuners do this. I made sure to let my tuner know 93 is readily available in my area and that I would never put in anything less.

I haven't seen that episode, but I know those guys are very well versed in engine building and dyno testing. I also know they tend to test almost exclusively on carbureted setups, not that this should matter in the end. There are just way too many variables to declare what they have found to be indisputable.

Here is another interesting take on things. Andrew from CSP testing on our actual platform:

[ADVMax]

With a stock LS at 10.7:1 or so compression I tend to like to give it enough octane so it doesn't have to kick the timing back so far trying to compensate for knock.

[RS/SS '10]

I watched that episode as well, did not make a whole lot of sense to me.

[Iron Lung Jimmy]

Weren't they using a carbureted engine?