This might be a weird question to some people but is there any problems say if I filled 1/2 of my gas tank of 90octane and then the 2nd 1/2 with 87octane. Because that has happend b4 when my parents have used my car then put some gas in it then I fill it up right after? (one at husky and one at petro canda)?............or any problem just filling it up straight with that kinda vpower gas from shell or super clean from petro which is like 94 octane?

SEARCH, your car runs on 87. If you fill with half 87 and half 94 your octane is around 90. Anything more than 87 is a waist of money without forced induction or modified timing.

I dunno about that, my car has a little more pep to it with higher octane gas, and it helped me old Buick out a lot. 1988 LeSabre, T-Type. Original 3800!

Using higher octane in a low octane car means all of it wont burn leaving carbon depiosts on the valves. Reason being all of it wont burn. The octance rating is simply the gas resistance to burn.

Using lower octane in a higher octane vehicle will retared the timing.


- 2004 Cavalier - 124k, owned since new

Here we go again with the octane BS. Andrew, for what it's worth, I have done a test with my 98 Z using 87, 89, & 91 octane. NEVER did I have a carbon build up problem in my car. I do get more pep using 91 octane. I spend the same amount for gas when I fill up since the 91 burns more effeciently than the 87 octane. Simply stated, I use less 91 octane to go the same mileage using 87. None of the three octanes listed will hurt your car. Going higher without doing mods will hurt.



98 Z24

RIP Specks

Why not try 110 octaine raceing fuel ? It should run real good + you get that great cam2
smell everyone loves !!

Just remember to get unleaded as leaded will kill your cat.




Semper Fi SAINT. May you rest in peace.

Wikipedia wrote:A common myth amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this is mostly false�engines perform best when using fuel with the octane rating they were designed for and any increase in performance by using a fuel with a different octant rating is minimal.

Complete article for your education Octane Rating

^^^ You may have an article, but I ran the tests on my car and know for a fact with my car that the higher octane worked better. See my prev. post.



98 Z24

RIP Specks

ZSleeper wrote:^^^ You may have an article, but I ran the tests on my car and know for a fact with my car that the higher octane worked better. See my prev. post.

Were your test under controlled conditions? I've seen tests that back up the article I posted before, I just don't have links right now. You'll have to excuse me if I'm a little skeptical about some test performed by someone under non controlled conditions with reported results like "I get more pep with 91 octane" Did you use accelerometer data to measure this "pep" or was it just a feeling you thought you felt?

There have been tests done that put the limit of human perception of change at 5% meaning it takes at least a 5% difference for it to be percieved by us. If your car did 0-60 in 8 seconds, for you to tell a difference it would have to now do 0-60 in 7.6 seconds or less. Do you think the change in octane caused your car to accelerate 5% faster? I'd kind of doubt it.

It is not worth getting into a contest on this subject. I know what my personal test concluded and am happy with the results. I know that I had a guy that I work with switch from 86 octane, yep New mexico has 86 not 87, to 88 and he also noticed a difference in performance and throttle response. Two of us can't be wrong. You can go ahead and go by the reports and I'll go by my own personal tests on the road.



98 Z24

RIP Specks

/\ /\ /\ Well that kinda does make sence seeing how our cars call for at least 87 octane
so I can see where 86 would pose a problem. And 91 isn't too much higher, besides if you think about it the higher the rateing the less likely to get pre-ignition caused by heat. Now if its one thing Gary has where he lives its heat ! So I myself find it completely plausable that when dealing with the high New Mexico heat the cars probly Do run better with slightly higher rateing due to the outside temp being so much higher. Think of it like this, sure it WILL run BUT the computer may have to pull out some timeing to prevent detonation and as we all know retarding the timeing DOES take away from engine output. So to regain that output swithing to a higher octane to get rid of detonation and the computers need to retard the timeing makes perfect sence to me.

Now true you'll hit a point where it's not worth it but for hot New Mexico days 91 does make sence.




Semper Fi SAINT. May you rest in peace.

It's ironic that you guys are missing a key point here....

All of these cars are controlled (in the stock incarnation at least) by the ECU, which is designed to retard the spark when the knock sensor starts to detect detonation. (to prevent wear on the engine).

The fuel you use as well as a wide variety of other factors (such as air temperature, air pressure, engine temperature, air flow, spark plugs, electrical resistance, engine load, etc. etc.) including the compression ratio, and bore/stroke ratio contribute to when your engine starts to cause the fuel to pre-detonate ("when" being at what RPM).

Let me break that down for you....

Higher octane = more resistance to detonation

more resistance to detonation = less detonation

less detonation = less knock

less knock = less DETECTED knock

less DETECTED knock = less retardation of timing/spark by ECU

A performance motor will suck-ass on crappy gas, whereas a suck-ass motor will not really see much performance gains from 110 octane race fuel....

The better the motor the more the difference (motor and ECU that is)...
The crappier the motor, the less difference...

any questions?

If you spent the extra money for the bigger/better motor, it's probably worth the extra two bucks every fill up for the premium gas. If you didn't then get the cheap gas, and stay out of the fast lane.

In my 93 Cav I can't tell the difference (between 87 and 93 octane) other than the car is smoother during driving, and acceleration..y'know less hesitation...

In my Civic, I can feel a huge difference, especially at the top end...

And then we get back to the differences in the motors... a Z24 ECU is tuned differently from the factory than the Ecotec 2.2, or my old 2.2 liter motor. That programming difference could all by itself account for a noticable difference just based on Octane. The Ecotec I've never driven, so I couldn't say.....

Dude I was kidding about 110 race fuel. Come on man.

Your description or your brake down is exactly what Gary and I were talking about. Thank you.




Semper Fi SAINT. May you rest in peace.