Like most modern GM cars that recommend premium, the SS has the ability to adapt to low octane fuel. This is not accomplished with some magical sensor in the gas tank, but by how the ECM interprets knock information. If the ECM detects knock, it will decrement ignition timing depending on the frequency, severity, and placement of knock events. Most GM ECM's use a high and low octane spark table, and "slide" between the two, depending on knock status. I can't speak specifically for the E69 computer in the SS because 90% of it has not been cracked. Moreover, the LNF has the ability to vary cam phasing and injector timing, so likely more than just spark going on, but suffice it to say, any changes made to the engine maps are done by interpreting knock sensor data.

The safety margins generally employed by GM are very generous, and the mild knock that it takes to trigger the octane scaler does not reach dangerous levels in an unmodified vehicle. HOWEVER, the addition of the factory turbo modification (stage mod) exceeds the ability of the ECM's octane scaler to guarantee safe operation under all circumstances. This is why the kit comes with a sticker mandating high octane fuel instead of merely suggesting it. With a forced induction motor, detonation can cause severe damage in less time that it takes for the knock sensors and ECM to adapt.

A word or two about octane. Octane refers to knock resistance, and knock resistance only. High octane fuel is not more powerful, more efficient, or cleaner burning than low octane fuel. In fact, cars that do not have the ignition timing specifically tuned to take advantage of high octane fuel, will actually see a slight decrease in MPG when running high octane fuel. I did some testing on a long trip with a stock LS1 powered vehicle tuned for premium fuel. I still got slightly better MPG with regular gas, although it was extremely difficult to keep from triggering knock retard, which will toss your MPG out the window. The fact that some oil companies only put their best detergent package in their premium fuel is irrelevant to any discussion of octane. For years, premium fuel was promoted as being better for your engine, and this myth persists to this day.

 

I use premium, preferably 93 octane; 91 in a pinch.

It's a small price to pay for peace of mind.

 

And this may sound crazy but I build dragsters as a hobby and the way I understand this is that a higher octane fuel is as MisterMike said, NOT a better fuel in the general sense. But with cars that are leaning on the performance scale it is pretty much a must, the higher octane fuels burn slower and cooler, eliminating spark knock and Pre-det. I don't understand the particulars but I do know that while my LT1 is running regular 87 oct. my two street beasts would grenade on 87, and I know this because one of them did. Neither are very big, ones a 89 Vette with an 04 LS1 swap it's been supercharged and has had some extensive tune work and the shop that did the work actually recomended we run Cam2. The other one is a 74 P-up with an extesively built 400 small block, this is the one that blew up, was trapped out of town about three years ago when we had the fuel spikes, station I hit was out of premium and mid, mind you I rolled into the place my fuel cell was literally dry, so I took my chances thinkin 30 minutes would be okay. I was about 5 from home when it happened, blew a hole in the sidewall of No.6 cyl. I know were not talking on the same levels of importance, but now if I'm told not to run below, I won't no matter what I'll sit or hoof it first, and don't go runnin real high grades either, my truck loses almost 8/10ths in a quarter on cam2 cmp. to street fuel

 

Very well explained. These are the accurate facts on this.

For marketing GM likes give the owner the option with RECOMENDED. This way it may not prevent someone from not buying a car due to a REQUIRED that was used in the past on all of the performance engines.

General rule is the engine will lose around 20 HP depending on the engine application.

Also it will not will not void your warranty. Now if it said REQUIRED then it would.

The bottom line is there is no real right or wrong answer here as either will work and it is up to each and every driver to choose what he or she whats. more Power or a few cents saved per gallon.

It is really that simple.

 

93 octane(preferrably BP/Amoco) with the occasional 100 octane(for the sweet smell).

 

Now, I've heard that if you use premium, after a while your car will require it.... Is this true?

I run 93 in my 2.2, and I just don't really want it to require it soon...

I do know sometimes older cars will need it, or run better on it...this is true with my truck, and my Lumina is getting there...

 

Unless there is some old odd car out there I am unaware of this is false.

I used to hear old timers come up with a comment like this long ago but I know of no reason for it to be true.

Todays cars react fast to any knock and with the computers we have it is amazing how fast and how many things can change to adjust to keep everyting right.

Unless a car is stated as requires premium fuel they all were made to run regular. Unless you set up the timing or compression etc there is no need for it with.

Now in cars prior to 1970 Compressions would and could be higher and in those cases with the timing set up you can break a piston. Usally they crack in the ring land area.

Since 1971 most cars are set up to run on regular unleaded. There are reare acceptions but they are usally noted on the dash or manual that Premium is required. Series II 3800 SC and early Northstars are just two examples.

 

Yeah... The only reason I like using 93 is the additives and cleaners that they put in it. I know it's probably a gimmick, but in my mind it helps... I know Shell has has their brand in their premium, and I like it to help clean the injectors to keep them nice. I really like the Chevron, but we don't have those stations around here...

As for my truck, it just runs rougher on regular. Don't know why...it didn't use to do that, but it does now...and I'm not the only one that notices it. My dad noticed it and so did my grandpa. Who knows why...probably just part of being old...

 

...could be you need a top end cleaner....carbon will raise your compression without you even realising it....and as usual its not the same amount in all cylinders so you wind up with up to 8 different compession ratios..91/93 might just smooth it out

 

Yeah, that wouldn't surprise me...