CMcCarthy

The owners manual on my GTO recommends 91 or better, but specifically says you can run 87 if you want. It says performance will be decreased, but it won't harm the engine. I'm sure the decrease is due to the ECM reverting to a less aggressive timing map.

MrDude_1

iTrader: (4)

yup.

after it detects so many knock counts across the map, it swaps to a low octane table.
it also does that if you MAF goes bad, or some other trouble codes are thrown...

heres the high octane and low octane timing maps for a 2002 camaro.
compare.

NOSjohn

iTrader: (9)

IMO, with low octane fuel, if you're not hammering on the car and keep your driving low RPM, you will see no difference in fuel mileage. I've done it for years even on my boosted Buick. Only after a certain RPM (read WOT) do the timing tables change dramatically.

B T

Scan Gauge will read DTC's (diagnostic trouble codes), erase codes, turn off Check engine lights, show all trip
functions such as instant mpg, average mpg, highest mph on the trip, highest coolant temp on a trip, max rpm,
distance traveled, and gallons used.
Scan Gauge will show 4 gauges at once. Coolant temp, Gallons per hour, MPH, TPS, Air intake temp, Voltage, engine
load, open or closed loop, ignition timing, RPM, MAP readings (n/a on some), Works on OBD II ('96 and up)
gasoline vehicles

Anyone checked this one out?
http://www.trtturbo.com/newproductsindex.html edit: for new linky

mpg and all that jazz?

Nimbus2004

I read over this thread and just proved to myself yet again that some people will say just whatever comes to mind, without any basis in reality. All the people who tell you it will damage your LS1 engine by using 89 or even 87 octane don't know what they're talking about.

From my 2001 Pontiac Firebird owners manual, and I quote:

"If you have the 5.7L V8 engine (VIN Code G), use premium unleaded gasoline rated at 91 octane or higher FOR BEST PERFORMANCE.

YOU MAY USE MIDDLE GRADE OR REGULAR UNLEADED GASOLINES, BUT YOUR VEHICLES ACCELERATION MAY BE SLIGHTLY REDUCED."

Case closed. End of story. I have occasionally run 89 octane in my Firebird since gas prices are sky high and have noticed no discernible difference in most driving conditions.

Besides, the GM owners manual says you can do it!

StuntmanMike

iTrader: (2)

YUP! I tried 89 in my Formula ONCE...I just drove it normally as I always do, back and forth to work. I didn't notice any difference in performance or the way it ran. However, I got about 3mpg less on 89 than I normally got with 93. Next tank I filled it up with 93, and my mpg went right back up to where it normally was.

I'll never run anything other than 93 (0r 91 in a pinch) again.

EDIT: Damn Nimbus, way to bring this back from the dead, lol!! This thread is from 2005!

chuckd71

iTrader: (23)

It's pretty clear that some people here know what octane ratings actually mean and some people are of the blind 'it costs more so it's better' mentality. Use whatever gas you want, the car will run and you will get where you are going. We are talking about mass-produced plastic cars churned out by the million for the population at large, not Ferraris or Lambos.

Nimbus2004

LOL. I found it and other threads like it on Google because I wanted to see if lower octane gas would hurt my engine.

Gas is $4 a gallon around here, and I need to save a few bucks wherever I can. The difference in buying 89 and 91 gas can be hundreds of dollars a year.

After reading conflicting information on every single board I found, I decided to actually READ the owner's manual. (Which somehow nobody else figured out how to do.)

This has shown me one thing, the marketing gurus basically OWN the public. After doing extensive research, there is no difference in the quality of 87 and 91 or 93 gas whatsoever. The higher octane just has a higher resistance to detonation. That's it.

Since our engines are designed to run with either one, but perform slightly better with "premium" gas, unless I'm going to be street racing every day and beating the $hit out of my car, 89 will work just fine.

jay7199

iTrader: (9)

mshadow

Not sure why people buy performance cars but can't afford the $.15-20 difference between 89 and 91 or 93.

WeeWolf

iTrader: (16)

Hell my car ran 11.80 at the track on 87 with no spark knock!

MrDude_1

iTrader: (4)

first.. thanks for bringing back a thread from the dead.. lol.

second.. ignorance is bliss.

let me try to explain what you're looking at.

The owners manual is 100% correct. It WILL NOT HARM the engine running 87 octane.. the lowest octane street legal gasoline sold in the USA.

So you can be 100% assured you will not harm your car. Now notice the owners manual does not mention MPG change.


There is one.
I dont know how knowledgeable you are when it comes to automotive engines, so forgive me if it sounds like im dumbing it down but im going to start with the basics and work up from there, hopefully answering all your questions you didnt even know you had.

First you need to know what detonation is.
Detonation in simple terms is an abnormal burn of the fuel in the engine. its when the fuel explodes early. imagine the piston is coming up and you explode the fuel charge early.. the piston is still going up, but its compressing the expanding fuel/air inside the engine, making this huge pressure spike.
that spike of pressure is actually powerful enough to damage the engine. you can even hear it.. it makes a pinging sound, or a knocking sound.
Detonation can crack pistons, lift heads, etc... all you need to know is, its very bad for the fuel to burn too early.

so what is octane?
Octane in very simple terms is fuels resistance to burning.. Another way to think of it is "how fast it burns"... Not how much power it can have, but how hard it is to ignite quickly.
low octane ignites easier the high octane.
so lets say you have a high performance motor, with alot of compression, it goes to light off the fuel, and it goes too fast.
it goes off fast, the piston comes up the rest of the way.. the pressure spikes and... you get detonation(aka knock or ping)
if you put a higher octane fuel in that motor, the fuel is slow to burn. its still starting to burn, as the piston comes up... goes past center, and you dont get detonation...


If this is true, why can i run 87 octane in my LS motor?

You see, this engine, like ALL modern engines, has whats called a knock sensor. it "hears" this knock/ping from the detonation and pulls back timing.
by lighting the timing later, it stops the detonation... but this takes away power and efficiency. meaning.. for the same power, you use more fuel. so driving down the highway, you wont feel any diff.. but you're using more gas.



So in a nutshell what is my LS1 doing?

you put cheap gas in.
it hears knock.
it pulls back timing.
it still hears knock.
it goes into a "safe mode" where it runs off these "low octane timing tables"
engine is perfectly safe, but you lose a few MPG.
driver cant really tell the diff, but will fill up sooner.


so this brings us to the big question...... WILL I SAVE MONEY ON 87 octane gas?

short answer is, probably not.
but there is only one way to tell for YOU in YOUR CAR in YOUR LOCATION. (weather, altitude, driving style, etc all play a role)

First, KNOW YOUR MPG on premium gas. lets say you get 23mpg avg..
now, get your mpg on regular gas... lets say you get 19mpg on that.

now look at gas prices:
locally i pay 3.20 for regular, and 3.40 for premium. so:

for 10 gallons of gas:
34.00 dollars for 10 gals of gas at 23 mpg = 230 miles = 0.1478 dollars a mile
32.20 dollars for 10 gals of gas at 19 mpg = 190 miles = 0.1694 dollars a mile


so when I want to SAVE MONEY on gas, I want the lowest dollar per mile.. on an LS motor, that will be on premium gas.
I also get a longer range for my tank.

You do the math for yourself, and you will know what works for you.
Either way wont hurt your car, but just because the dollar number is lower at the pump, doesnt mean you wont be back that the pump sooner.

MrDude_1

iTrader: (4)

so..... its pretty clear here you dont know what BSFC is... or how efficiency of your engine effects your pocketbook more then pump price.

ignorance is bliss.

MrDude_1

iTrader: (4)

If you really want to avoid the "marketing gurus" get out the pen and paper, add up whats going on.. and with a little math, you will know if you are saving money with a lower octane fuel or not.

if you really want to be pissed about marketing guys... go compare your MPG on ethanol blended fuel with non-ethanol gasoline.... you are paying hundreds a year extra for a huge government con... and you dont even know it.

NemeSS

iTrader: (127)

My dd 4.8 rcsb actually gets better mpg with 87. I put 93 once and it felt significantly more sluggish and mpg decreased significantly. It loves the low octane fuel. But I run 93 in my other ls cars

Cronic_Moronic

My camaro is noticably sluggish on 89 or lower gasoline. And gets poopy for gas mileage.

I run 92 and get 20+mpg consistently.