Humm... for awhile I was sure I was putting in Regular with an octane rating of 87 will I decided to switch to Pemium with 92 Octane rating. I ran the tank nice and dry, so my question is, is this alright or could it possibly damage my engine. Or will I slowly notice the effects over time as I continue to use a higher octane rating.

_________________
305 TBI 1989 Camaro RS
Transfer Project: Smashed 1990 IROC-Z 350 TPI

 

87 WOW, I have always put 94 in mine, but mine is not a stock motor

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1986 Iroc z28
4bbl 350 V8 430 hp
300 shot NOS
6 spd Manual
20" Iroc replica Rims
2, 12" Alpine Subs
4.11 gear ratio
1/4 mile - 10.52s and 10.86s

 

GM says that 87 is fine for that motor. I think the compression ratio is like 8.x to 1 on the tbi motor, so you shouldnt NEED 93. That said I WOULD put the good stuff in. You probably will not notice a major performance increase, but you may see a pretty good boost in mileage.

 

Milage boost is what I'm looking for, over perforamce. Daily driver

 

There's no more energy in 92 octane pump gas as there is in 87. Octane is the fuels resistance to detonation. If your engines doesn't ping (spark knock) with 87 then you're not going to notice any difference with 92 except a light wallet.

The chance of increased milage is possible however I don't think it offsets the extra cost of the fuel.

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87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

I'll try it for 3 re-fuelings and get back to ya.

I'll count how much it cost, how many miles, vs. regular cost and miles, and compare the two. See if I gotta better milage and if the cost was within excepable range. Premiun is only 1.22 here

[This message has been edited by un4givin89 (edited August 08, 2001).]

 

Yes, the higher octane you use will produce better combuston. Better combustion will produce slightly better fuel efficiency.
Ive noticed the effect form higher octance gallon for gallon 85 vrs 91, 91 would get about 2/3 MPG more than 85. At leat it paid for the 25cents more per gallon cost.
SSC

 

How bout this:

QUOTE:::
The higher octane you go, the less fuel mileage you
will get. Higher octane burns much slower and is only
beneficial in very high-load situations, not for daily
driving.


Someone told me this, thoughts??

 

As usual, I have to agree with Steve; higher octane by itself has little or no effect on your gas mileage.

I have been doing EXTENSIVE experiments with various octanes and the modifying my eprom accordingly. If you advance the spark and lean out the engine, then YES I can exceed the gas mileage using 94 vs 87. But this required extensive modification of the eprom. I actually can obtain Highway mileage of 30 US MPGs with my L98. Under the same situation with my original tables in my eprom, my best with 87 was 25 US MPGs.

However, this 20% increase in gas mileage requires a 20% increase in cost. So, from a money point of view, its the same cost.

I am now trying to modify my eprom by backing of the timing and reducing the "leaness" of my mixture, so I can return to burning 87. I figure that if I can get 28 US MPGs and using 87, I actually work out paying less.

My goal is also to obtain the same performance with 87 as I do with 94.

 

errr.... that was way over my head, so you must be right. Guess I'll just stick with regular

 

Glenn's experiments are correct. Higher octane gas burns slower than lower octane gas. Therefore in order to reep any befits of the higher octane gas, you must increase your timing curve so that the spark plug creates the spark earlier giving the gas more time to fully burn.
*
Unless of course you are experiencing any degree of Knock Retard already with the 87 octane, then the higher octane gas should help cure that problem, but you probably won't know if you're getting any KR without a scan tool to monitor it with.
*
And yes, using higher octane with a higher timing curve will produce more power to a certain extent. In my Turbo cars, on 93 octane I can run about 17psi of boost and run a 1/4 in the mid-12's. Put in 116 octane leaded with a chip programmed for it with the same boost and run about .3-.4 tenths faster, but this also allows me to crank up the boost to 25psi with then cuts another full second off the 1/4 times to mid/low 11's

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Rob
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Just curious, when I bought my camaro the guy told me not to use the cheep gas, use the 91 or better at least.

What happens if I do use the regular 87? My cars an 84 305. Is the car gonna run like crap or something?

 

Personal experience between 87 and 94 with my old 92 RS 305 TBI, I got an extra 80km out of a tank which in the end result off set the cost, plus it just felt stronger. anyways I always run 94 ... if it's my GTA or my old 81 OLDS delta 88 307.

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1989 GTA 350 TPI
Stock:
- T-tops
- Dual cats
- 9-Bolt 7.75" Rearend
- 3.27 gears
Mods:
- Dynomax Super Turbo Muffler

1992 RS 305 TBI - Sold

 

I also concur with Glenn's observation.

Higher "octane" gas usually has additives to reduce its combustion rate. Most often the additive is either alcohol or MTBE. Neither of these has anywhere near the heat content (energy) per unit volume (gallons) that gasoline has; in other words, they are inferior as fuels. So the higher the proportion of them there is in the fuel, the more fuel has to be burned to release a given amount of energy.

As a result, any specific car will always get the best mileage out of the lowest "octane" fuel that will burn in a controlled manner in it, that is, as long as it doesn't explode uncontrollably ("ping", "spark knock", etc.). The only time you can get better mileage is if the ignition timing can be advanced farther to allow enough time for more complete combustion of a leaner mixture. So, to actually get better mileage out of premium, both the timing and fuel delivery curves have to be adjusted. If that doesn't happen, then the mileage will be worse.

So, un4givin, your friend or whoever is right. If you discard all the marketing hype and chest-beating on the subject, and stick straight to the facts, that's where they lead. Basically, if your engine's CR, driving habits, etc. etc. don't cause spark knock with regular, then you're actually better off with it than with "premium" (regular gas mixed with extra alcohol or MTBE).

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"So many Mustangs, so little time..."
ICON Motorsports

 

I'll stick to reg. Thanks guys for all the interesting imput and views and facts.

 

I have been experiencing the "ping/knock" sound on acceleration with using the regular gas. When I went up to "87" on my last 2 fillups it was a lot less noticable. Now I plan to try the premium pump next. I'll probably trade the gas milage for the "no ping" sound. I can't stand it! Any other idea?

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86 Camaro Black SS Coupe, T Tops, Flowmaster, Custom Paint, Dunlop Road Kings S/R tires, Wheel Country Directional Chrome Wheels,new charcoal & gray interior including seats and door panels, new carpet and headliner, complete front end suspension rebuild, new Valve seals, and more mods to come
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If you can hear the knock/ping, that IS NOT GOOD! It will eventually cause severe rod bearing damage or destroy your pistons if it is not taken care of, or possibly blow a head gasket.
An older car that used to run fine on lower octane may start to have detonation/pre-ignition/ knock/ping problems due to a number of factors:
1) EGR passage ways are clogged not allowing the EGR to function properly is common.
2) Excessive carbon buildup in cylinders, thus causing a higher compression ratio, which would also lead to clogged EGR.
3) Fuel injectors clogged not allowing enough fual to enter cylinders.
4) Fuel pump weak not producing enough fuel pressure to feed the injectors properly.
5) Weak spark or too hot of a spark. Try colder spark plugs, test coil, new cap, etc.
*
I would tend to look at the EGR first, its the easiest to diagnose by removing the EGR, mine were clogged on my truck with less than 100k miles on it.
Either way, if using higher octane gas cures it, then its worth it! Unless you want to build a new engine That's what I'm in the process of doing now!


[This message has been edited by 2QUIK6 (edited August 09, 2001).]