The spread between 87 & 93 is as low as 20¢ around here, that’s why I use it, a tank of 93 is only 5 bucks or so difference

 

93 octane burns slower which has been shown to be better for injectors over time. Also some people say it's going to burn cleaner inside the motor. 93 octane isn't as hard on the fuel filter, either.

 

I don't understand how a "knock" rating is going to perform miracles with the mechanical parts of your engine.

Did you happen to check out the link I posted earlier?

 

so your saying that you are under the impression that you were paying for 3.5gallons of air when you were pumping fast? im not calling you a liar by any means but i just dont get how that works...i mean yeah a small amount of air will get it, theres really no way around it that i know of...but three or four gallons of air?

 

That was a great link, rch!

And, Thumper, I'd expect high octane gas to actually burn "dirtier", since it burns slower. Sure, we compensate a bit for that with increased timing, but we can't do anything about the compression. Therefore, I'd expect a higher hydrocarbon reading in the exhaust using high octane gas. You reach a limit on timing advance, and I think that happens too soon for complete combustion.

I also don't see why high octane gas would be kinder to injectors either.

And, wouldn't unburned hydrocarbons tend to "carbon up" the cylinders and spark plugs more too? (Leading to the famous "breaking plugs" problem when they are changed)?

These are just questions. I'm certainly no expert! But, I read a lot and EVERYTHING I've ever read or heard from reputable sources say don't use gas having a higher octane rating than your engine needs.

I also appreciate that using high octane gas with advanced timing gives more power. (Since it gives a nice, controlled "push" on the piston during the downstroke rather than a harder, faster, explosion). If that's what you're after, fine!

- Jack

 

So, those thinking they will get a little of both worlds, performance and economy by taking the middle road and ordering a 89 tune and running 89 octane is pointless? its either 87 or 93. why are 89 tunes offered? just asking because i was about to order the 89 tunes cause I dont want to pay for 93 unless its worth while. performance and $$ in the long

 

Kyle - the octane rating or "knock" rating has NOTHING to do with performance or economy. It is merely the formula required to run your motor without "pinging". I won't get into pre or post detonation or timing or compression or all the other things that DO affect performance and economy...but if your truck was built to run on 87, anything else is a waste of $$$.

There is a link above that gives a decent explaination of high performance vehicles and fuel. It's worth a read and there are other sites that explain, in great detail, why 93 is NOT better for a motor than 87. That's another thread though.

 

It's not a matter of if it was built for 87. It's a matter of tuning, not production or manufacturing. Agreed, more octane allows for more timing to be pulled from the motor which in turns gives you the more power and better fuel economy.

We can argue all day long about this and that but the answer is cut and dry.

Yes 93 octane is better for mileage. Not only am I saying it is, from my own testing, but someone who has tuned thousands of vehicles, etc.

 

I don't believe 93 burns any slower, but rather has a higher resistance to knock than 87.

In some vehicles running 93 will allow the computer to advance timing slightly, and add a little power, but not as much as you would get from a full blown premium fuel tune.

 

bingo

 

I run 87, gas prices for 91 are way too ridiculous in CA right now. I drive mostly highway, and on the 87 tune (highway only) i am consistently getting between 18.6 and 19.2 MPG on my 87 Troyer Performance Tune. I keep it at or below 70mph the whole time.

 

I'm not sure that a designer of a 15:1 motor would tune for 87 - the engineering of the motor is what calls for the octane rating, not the other way around.

 

HOLY CRAP!! You serious? Man I might have to expierement mith that.

 

Regardless of how fast you pump gas is not going to change the amount of gas you pump ... Think about that for a few seconds ...

What are you talking about? 15:1?

 

You said the above. ^^

It IS a matter if it was built for 87 or not. Some motors are built to run 110 and you aren't going to tune them for 87.

The answer of 93 giving you more MPG's is NOT cut and dry. If you ran 87 in a motor that calls for 93 - you will see a drop in MPG but you don't get a gain by running 93 in a motor designed for 87. It doesn't work like that. Can you create a situation where it can - sure, but it ain't as a daily driver and therefore a moot point.

Does you car have a knock sensor? What do you think it's function is?

There is less energy in higher octane fuel and adjusting your timing is not going to net you an increase that you can measure.