Octane rating

**redls1** · 06-30-2011, 02:43 PM

I understand octane rating and stuff for the most part. Are cars not made to run shitty ethanole or this crap now a days? Walmart is running a special use your credit card and save 10 cents a gallon. We pay it off every month anyhow. I told my father in law and he goes good you could run 89 instead of the 87 it says in the owners manual. Its not a performance vehicle and will always be under warranty while we own so whats the point? My car is only a sentra but a spec v and while not really a sports car is made to run on premium. I get 31 mpg on the highway. Is it really worth it run 89 octane when I get the same gas mileage on 87?

**310stanger** · 06-30-2011, 02:55 PM

If the engine calls for 87, you dont benefit the vehicle to run a higher octane. Why? It has everyting to do with compression ratio and ignition timing. Octane is the resistance to detonation, the higher the number, the higher the resistance. So 87 "burns" quicker then 93 does. You can hurt a car by running too low an octane fuel, but never too high. You just flush money away. The only benefit one could get on running a higher octane in a car that calls for 87 is the fuel itself might be higher quality

**redls1** · 06-30-2011, 02:58 PM

Thats what I thought or have read before. He has a 2001-2003 f150 with the 5.4 v8. It says 87 but he swears it is better with 93. He still gets shit gas mileage so being a v8 maybe but I still fall back to what was it rated to run on? My car compression is different.

**310stanger** · 06-30-2011, 03:13 PM

Originally Posted by redls1

Thats what I thought or have read before. He has a 2001-2003 f150 with the 5.4 v8. It says 87 but he swears it is better with 93. He still gets shit gas mileage so being a v8 maybe but I still fall back to what was it rated to run on? My car compression is different.

He is flushing money down the toilet in that particular application. But if the placebo is working for him. let him be.

Your motor in your car has slightly hotter ignition timing then the other qr25des in nissan vehicles. I'd run what nissan says to run. Premium.

**redls1** · 06-30-2011, 03:17 PM

Oh yeah I run premium but cant get it through to him to run anything different. Oh well

**pajeff02** · 06-30-2011, 05:37 PM

Agree with 310stanger. It is a common misconception that higher octane means greater power. In reality, running a higher octane fuel can sometimes mean a loss in power unless combined with an advance in ignition timing. It is tougher to break the chemical bonds in higher octane fuels and that is what makes them resistant to pre-ignition. Therefore, they also require an advance in timing to allow for the combustion to occur at the optimum moment. In a car like the '98 - '02 F-body, the PCM contains both high and low octane spark tables for ignition advance.

**SeVeReDiStOrTiOn** · 06-30-2011, 05:52 PM

Safeway has the same deal except you don't have to use a CC...but you have to spend $50 or more. Their gas doesn't have detergents though.

**damianj03** · 06-30-2011, 07:26 PM

ok so what to run in a 98 ls1? 87 or 93 whats best?

**bouigha123** · 06-30-2011, 09:33 PM

Im pretty sure you wanna run the lowest you can without pinging, however my f body wont get anything lower than 93

**vonskeezy28** · 06-30-2011, 09:36 PM

Originally Posted by 310stanger

If the engine calls for 87, you dont benefit the vehicle to run a higher octane. Why? It has everyting to do with compression ratio and ignition timing. Octane is the resistance to detonation, the higher the number, the higher the resistance. So 87 "burns" quicker then 93 does. You can hurt a car by running too low an octane fuel, but never too high. You just flush money away. The only benefit one could get on running a higher octane in a car that calls for 87 is the fuel itself might be higher quality

pretty much said it all right here.. high compression cars definitely need higher octane... if it says on your manual to use regular unleaded, and youre using premium unleaded, you are definitely wasting your money..

**ls1camino** · 07-01-2011, 03:38 AM

To give you a comparison...in my GTP if I run 93 octane, I get MAYBE 1-2 degrees of Knock Retard on a hot day. If I put 87 into her, I will get over 5 degrees. Knock Retard is the engine pulling timing to prevent detonation. For this to happen, you have to have detonation, so this is a BAD thing.

**tnthub** · 07-01-2011, 06:02 AM

The goal is to use the lowest octane that does not ping. (Very general and non technical description): Higher octane creates a bigger bang but also takes more juice to do it so using higher octane fuel in a vehicle designed for low octane typically results in lower fuel mileage and harder starts, especially in cold weather.

**tornado** · 07-01-2011, 11:23 AM

I can still get ethanol free gas,haha. but not sure how long,10 % ethanol lowers your octane rating about 2 points,so if your car calls for 87 octane,put 89 in it. Ethanol blend gas is crap as its just a filler and the idiot law makers have no idea what it even is or does,they prolly never dont even pay for there gas. They only people benefiting from this is the corn farmers.

**FasstChevys** · 07-01-2011, 12:36 PM

Originally Posted by redls1

I understand octane rating and stuff for the most part. Are cars not made to run shitty ethanole or this crap now a days? Walmart is running a special use your credit card and save 10 cents a gallon. We pay it off every month anyhow. I told my father in law and he goes good you could run 89 instead of the 87 it says in the owners manual. Its not a performance vehicle and will always be under warranty while we own so whats the point? My car is only a sentra but a spec v and while not really a sports car is made to run on premium. I get 31 mpg on the highway. Is it really worth it run 89 octane when I get the same gas mileage on 87?

No, the 89 octane isn't going to help you.

**FasstChevys** · 07-01-2011, 12:43 PM

Originally Posted by tornado

I can still get ethanol free gas,haha. but not sure how long,10 % ethanol lowers your octane rating about 2 points,so if your car calls for 87 octane,put 89 in it. Ethanol blend gas is crap as its just a filler and the idiot law makers have no idea what it even is or does,they prolly never dont even pay for there gas. They only people benefiting from this is the corn farmers.

You have no idea what you're talking about. Do some reasearch before spewing this garbage.

You're the one that has no idea.

Alcohol has an octane rating of approximately 113-ish. Blending alcohol in to gasoline RAISES the octane. Get a clue!

**tornado** · 07-02-2011, 06:19 AM

Originally Posted by FasstChevys

You have no idea what you're talking about. Do some reasearch before spewing this garbage.

You're the one that has no idea.

Alcohol has an octane rating of approximately 113-ish. Blending alcohol in to gasoline RAISES the octane. Get a clue!

Read this

http://www.fuel-testers.com/gasoline...hanol_E10.html

**tornado** · 07-02-2011, 06:20 AM

Ethanol is bad for your car no matter what,E10 that is. It creates moisture/water over time.

**TLS_Addict** · 07-02-2011, 06:34 AM

Originally Posted by 310stanger

If the engine calls for 87, you dont benefit the vehicle to run a higher octane. Why? It has everyting to do with compression ratio and ignition timing. Octane is the resistance to detonation, the higher the number, the higher the resistance. So 87 "burns" quicker then 93 does. You can hurt a car by running too low an octane fuel, but never too high. You just flush money away. The only benefit one could get on running a higher octane in a car that calls for 87 is the fuel itself might be higher quality

I have heard much of this and even did a google search a while back and confirm much of this.

Praise the internet!

One thing though, I was under the impression that TOO high of an octane can do more than just hurt performance. Is there any validity to engine failure with running too high of an octane, such as race gas?

**pajeff02** · 07-02-2011, 06:53 AM

Alcohol in fuel is a drying agent if anything -- it absorbs H2O. That is why a lot of guys run TC-W3 oil, or other additives, to keep their fuel system seals from "drying out". Again, other than anti-knock properties, you have to combine high octane fuel with advances in ignition timing to see a power benefit.

As described by Greg Banish in his class -- the fuel molecules are looking for dance partners, and it is harder to pair up with a high octane fuel and make the chemical reaction we call combustion. That is why the ignition event has to happen sooner, to allow time for the pairings to happen before the piston reaches the optimal point in its travel for the expansion of combustion to send it back down its bore.