Premium recommended?
 

When Gm says this, what do they really mean?

Do they mean you should only use 92+ octane?
Do they mean you should use 92+ octane when possible, but the car will "live" on 89?
or does it mean you can run it on 87 octane and occasionally put the good stuff in it or put in a octane booster?

I had a 2006 Impala SS with the 5.7L and it recommended the Premium and that is all I used. I always wondered though.

Yeah, I'm interested in the answer too. To me it sounds like they'd rather you use 92+, but you can use a lower grade with a slight loss in performance. Now it seems if they only wanted 92+ they'd say high grade only.:iono: Least that's my take on it.

This conversation has already been had elsewhere - but the compression ratio on the LS3 (V8) needs premium. Same as the LS2 (the '1 could run on crude oil though).

Its like the Vette in the stats, recommended but not required...The compression on the v6 is higher(11.3 vs 10.7), but does not require premium...You will lose some top end power as the computer dials things back, but lots of Vette guys are running regular right now with no ill effects other than the loss of some top end...Sorry tried to copy the table from the press release, the spacing did not come over well....

http://wilsonniblett.wordpress.com/2...press-release/

Thanks. That is what I was looking for. I am fine with losing a little top end, since all I see where I live is the weak V6 'Stangs. I just did not want to do any major damage.

There has been a lot of confusion, but it appears to be like the Vette in that regard...

you will lose more than just top end.

lower octane fuel will hurt your gas mileage in a car that is made to run premium and it will also pull from your power. yes you can run regular, but you are better off running at least 89 or higher or the manufacturer's recommendation.

i run 93 octane unless i cant find it then i will run 91 and ill add a bottle of STP octane boost. ive run 89 on one fillup but i only put 3 gallons in to get me to a place with higher octane gas. 87 has never touched my tank.

another thing to keep in mind is that a 3 pt octane booster will not bump 89 up to 92 octane. Under the North American octane system AKI (Anti-Knock Index) pump fuel is graded as (RON+MON)/2. Meaning if a fuel has a RON (Research Octane Number) of 96, and a MON ( Motor Octane Number) of 90 its AKI would be 93.

basically, you add the octane rating to the MON. so for our 89 octane the MON is roughly 90 and the MON is 88. add 3 to 88= 91

91+90=181
181/2=90.5 octane.

so in effect you are getting 1.5 points even tho the bottle says 3 pts.




here's a good writeup with MON and RON testing of octane boosters

http://volvospeed.com/Reviews/octane_boosters.html

ONLY 91 here in Cali, except for the Union 76 100-Octane unleadded racing fuel @ 15.00/gallon:mad0259:

and thats part of the pollution problem over there... that on top of the fact that there are billions of cars on the road over there...lol

i be running the highest avail. which is 93 here. i want all my ponys acounted for.

93 during the week, 112 on the weekends...lol

How does 91 increase pollution?
Is that 112 unleaded?

comparing it to 93 and the fact that with that being the highest available, most people will put 87 in their cars as it is the cheapest, lowering your emissions and performance. multiply that X's the number of vehicles on the road out there in Cali at any given pt in time, and you wonder why everything has a sticker that says "has been known to cause cancer in california" its not the product, its the shit-ton of smog created by the millions of cars on the roads over there.


and yeah, its unleaded... tho they have 113 leaded but i wont mess with that.

My 2 cents worth
 

With the new computer controlled engines, it would appear that octane rating is not as critical to prevent pre-ignition as in older engines. These engines will self adjust and run on 87 octane. However, as stated by others in this thread, you will lose some performance and in my experience some gas mileage (1-2mpg).
Now the economics. 92 octane is generally $.20-.25 more than 87 octane. My logic says that in a typical 20 gal. fill up, I'll pay roughly $4.00-$6.00 more per tank. In my opinion, that aint bad for a tank of higher performance, and better gas mileage. Just a thought.
:thumbsup:

while computers in automobiles do self adjust to run on lower octane gas, thats whats hurting your performance. they cut back the spark timing to prevent detonation (combustion cycle preignition) which means you dont start the combustion cycle till later in the rotation of the motor which means you arent reaching your full power potential

i spend 45 bucks to fill my car up (roughly) 14 gal tank, i fill up with 10-11 gal (cus i dont run my car down past 1/4 tank cus it can be detrimental to performance and the fuel pump). as ive stated before, i wont put 87 in my car. its a rare occasion that i'll even run 91 or... dare i say it 89.

93 for me baby :thumbsup:

Greg you really know your shit, I like you man.......lol :respekt::drinking:

So us Swedes that have 95 octance standard, 98 premium won't have to worry about all this then, huh?

thanks. i try to share my knowledge as much as possible, usually to help, but sometimes to shut others up. :thumbup:

its hard fighting against all the ignorance in the world (and on this forum as of late)




98...bastards...lol



unless your rating system is different than ours...

I'm with you 100%!!!:clap:

When a bottle of octane boost (or snake oil as I call it) says 3 points it means from 89 to 89.3 not to 91. Total waste of money.

I hope you all know why/how the computer knows to pull ignition and up the fuel/air ratio

KNOCK, that's right, the engine knock sensor, from preignition

it's NOT good, just because the engine is smart enough to retard ignition and richen the fuel does not mean it's good to run 87

I would run 93 all day. however, even the vettes with trhe LS3 can run on 87, you jus lose some power. I don't remember who said it earlier, but the higher the octane rating, the WORSE fuel economy you get because it burns at a higher rate.

What we should all be hoping for is E85 capabilities, because that burns hotter than 93 and will give you some extra horses when using it.

wrong, e85 has less energy, it's ethanol based, you'll get worse mileage

you want to run the lowest octane fuel you can, without predetonation, any higher is a waste of money

exactly right.... see post 7

knock = detonation... see post 15



wait a sec... so you say that the higher octane rating, the worse fuel economy... e85 is effectively 100-105 octane rating... e85 users will spend the same amount if not more to run it over gasoline due to the fact that e85 tuned motors tend to run richer than gasoline. so what they think they are saving on gas at the pump, they are more than paying back on the road.

and when it comes to horsies, the only real time that e85 outshines regular gasoline is when the motor has a high enough compression ratio to make use of the higher octane level of e85. most other times e85 runs slightly less hp than gasoline.



and here's a nice coverage (by the epa) about e85s stats
http://www.epa.gov/air/caaac/mstrs/2006_10_dunham.pdf

Different motor, but that has been my experience with my Cobalt SS/SC. I actually get better mileage with regular, but admittedly it is not scientific since I don't drive exactly the same every time, but it runs very nicely on regular, but I don't spend a ton of time in the upper part of the tach when I drive back and forth to work......

already touched on the first part...

and the second, you hit the nail on the head

Octane is defined as a fuel's resistance to knocking. There is no benefit if the octane is higher than what the engine needs. Engine knock occurs when fuel in a combustion chamber ignites before it should. This disrupts the engine's operation. But electronic knock sensors are now common and have nearly eliminated engine disruption.

The American Petroleum Institute says if you find that your car runs fine on a lower grade, there is no sense switching to premium. The Institute recommends following manufacturer's recommendation, but even those manufacturers say that it is more of a suggestion than a command (mainly cus a lot of people who buy cars that have a recommended 93 rating will still go and use 87 cus they arent pushing their car to its limits and arent worried about it).

but i will say this to any LT1/LT4 owners out there. our motors came with roughly 10.5-11.0 cr. thats high considering the cr's of the other vehicles produced in that time. too many times, ive had someone complain about their car bogging down, running rough, and just crapping out in general. i ask what fuel they are running, they say 87... well, there's the problem. 90% of them that switched to premium found the car running smoother and better overall. the other 10% had opti problems... go figure.

adding on that, the cr of todays motors that are rolling off the production line is going up every day. but with more advanced tuning and distinctive engine properties (ie:D.I.) it is more and more common to see high cr motors running 87 without problems.

Not wrong. In FI and high-compression applications; E85's natural ~103 Octane rating can have positive effects on performance. Mileage is a different story.

throw a turbo on it and run 3 tanks of e85...lol



that will net you some hp... not sure on mpg tho.
the main thing to keep in mind with e85 vs gasoline, is that gasoline gives you more bang (not necessarily for the buck tho) what would be cool is if they made a dual tank flex fuel vehicle that on acceleration would go off gasoline, but when cruising, would switch to e85....:iono:

Most of the time I drive for mileage, I would love to have the option of using E85, I don't expect better FUEL mileage, but of you look at your 19 gallon take there is less than 3 gallons of GASOLINE in the tank, even if it costs more its would be nice to use a renewable fuel (yes, it would be better if it didn't come from corn). Imagine walking up to Ed Begley and telling him you use less GASOLINE per tankful than his Prius does....The fact that it has higher octane and has the potential to deliver higher performance doesn't hurt either...

do a search for the sugarcane ethanol debate and read some of my posts about what needs to be done. e100 for instance

Do E-85 pumps have a larger nozzle than Gasoline pumps? Since E-85 will ruin an engine not designed for it, there needs to be some safeguard to keep people from putting it into their regular cars. I know if they don't there are going to be many people kill their car because they buy the cheaper E-85 not knowing you are not supposed to use it in a car not designed for it.
right now regular is running about $3.60 where E-85 is only about $3.10.

Someone would need to back me up on this, because I'm not sure...

but I do not believe that E85 will destroy your engine because of one or two tanks full. The biggest reason that E85 is limited to Flex-fuel vehicles is because E85 is corrosive to certain materials found in conventional vehicles. That's why Flex-fuel vehicles have different gas tanks, and different fuel lines, etc. But I believe than a 'normal' car will run on E85, maybe not well...but it won't destroy it right off the bat.


EDIT: Then there's also those big yellow fuel caps, and big yellow pump nozzles (that I've seen)...

the e-85 nozzle at the gas station is the same size as regular fuel so you can put it in any vehicle by mistake

most vehicles made within the last 10 years will handle e-85 without any issues if they are tuned to run on it

there are several companies making an e-85 conversion which consists of a converter box that plugs in between the injectors and the harness that runs to them,, it then has a setting for e-85(basically it just increases your injector pulse width about 30% and has an adjustment so you can fine tune it for your vehicle)

as for being corrosive,, i ran it a whole summer in my s-10 when i first had a carbed 5.3 in it, all i had was steel lines and the factory plastic tank and pump and a holley carb and it ran fine and did not do any damage to the steel or rubber hoses

many people running boosted engines are going to e-85 for the octane/ less detonation properties and the fact that when you run e-85 at the proper air to fuel ratio it will produce more power than gasoline but you need to burn about 30% more to maintain the correct a/f ratio

i work at a chevy dealership and a few times now we have had vehicles come in where the owner decided to try e-85 in there non flex fuel vehicle, the engine will be running lean, buck and surge and the ses light will be on with a few lean codes in it, drain them and fill with regular gasoline and they are fine

I wasn't meaning one or two tanksfull, I was talking about someone using it over a period of time, from what I have read and heard from experts, one tank will not hurt, but several tanks could not only ruin the Catalytic convertor, but cause detonation and a leaning out of the engine causing a engine failure. A carburated engine would not be effected as much as a fuel injected one computer controlled one, you could change the Jets to make up for the difference.
My advice is if your care is not designed to use it , Stay away from it, Why take the chance to save a few bucks.

if you run e-85 on a non flex fuel vehicle without tuning, it will run so bad i dont know why you would try to run more than a tank through the engine, some vehicles run so lean they will die out at stops and not start when cold

if you tune/program the ecm/pcm for the e-85 you will be fine

you can even get a handheld programmer that will tune your pcm to run on e-85 for most gm trucks that are not flex fuel from the factory

If all it is is a ECM reprogram then why do they have 2 different engine options, one with and one without and the E-85 cost more?
Seems to me if it was that simple then it would be standard on ALL engines.

factory flex fuel vehicles can run on straight e-85 or any mixture of gas and e-85,, if you program a standard vehicle to run on e-85 you must fill up with straight e-85 every time,, the factory flex fuel vehicles have a sensor to measure the alcohol content and can vary the timing and fuel to run on any % of gas/e-85

the aftermarket conversion boxes have a switch so you can go back to standard gasoline if you want to but you need to run out most all of the e-85 first, then fill up with gasoline and flip the switch back to stock

I was talking about factory engine options, so there is a difference... and as I have read that even if gasoline is rated as E-85, the actual content may be anywhere from E-80 to E-90... that means to run right a single program will not work effectively. It needs the sensor to measure the content of ethanol to program the engine for the best efficency.