Jus curious because the owners manual says a MINIMUM of 87octane is required, which kinda hints to me that w/ better octane it may produce better economy and power?

I know in most cars higher octane does jack, but in my awd loaded pacifica, 93 octane made a HUGE improvement over 87 octane. On the highway I'd NEVER see 19mpg or higher. I did it ONCE (19.3 or something..), and I'd hardly ever see over 14mpg city. Upon experimenting with 93 octane, I'd continually obtain 22-24mpg highway and 20-21mpg city. And it only cost less than $5 more per tank.

So. Are there any gains to be made running it thru the HUMMER or has it not really been experimented with?

Matt

 

Interesting. We use RON I believe.. but I'm not sure? I'm not a fuel expert.

I think next tank I'm gonna give 93 octane a chance and see what happens. I just dont wanna spend more money if I dont have to but if you say you can see noticeable increase I'm gonna try it.

 

In my manual it says to use no less than 91 octane, also I run 93 or higher if I can find it, it takes pinging away that I feel is associated with a lower grade of fuel. I'm no fuel expert, but when you hear something then try a different fuel and the noise is gone, well then you do the math.

 

Is that so? I wonder why mine says 87minimum? I have the 3700, do you have the 3500?

I'm def. gonna try the 93 octane in the next few tanks to see if there is a diff. What kind of mileage differences do you find between low grade and 93?

 

Important to note: More Octane does not mean more power

Octane is used for one critical purpose, to better control detonation in high compression engines. It actually is more like an inhibitor for the fuel that prevents it from detonating too early due to compression. That is why turbo and supercharged vehicles always use premium fuel, a lot of newer engines which are using direct injection systems also need a higher octane fuel because the compression levels are so high.

A lot of people confuse premium VS regular with the gas being better or higher quality and somehow making your vehicle run cleaner with more power. None of this has much merit... (although see the exceptions at the end)

Whatever the manufacturer has suggested for your vehicle is perfectly fine, on another forum I use (my other car is a Honda Fit) we have a lot of crazy eco guys... time and time again real world results find that regular fuel will get you slightly better economy in an engine designed for regular fuel (crazy huh?). But the difference is almost negligible.

The main thing you are going to get out of a premium fuel is a really great placebo effect

With all of this said there is some exceptions; firstly is that in higher altitude areas you will find that octane for regular fuel may be different than sea level areas. Less atmospheric air pressure means less compression; so they offer regular fuel with less octane in that region.

The second exception is heat... in the hottest environment you can find (maybe Nevada in the middle of a heat wave as an example) in a situation where your vehicle is prone to overheat... use a mid grade fuel. It will help prevent knocking due to excessive heat, although with today’s engines this is almost not even worth mentioning because the computer has anti-knock systems in place anyway.

 

Yes I know the "science" behind it. But like I said, in my awd 6-seater pacifica, if I got 13-14mpg city I was lucky, and if I hit 19.xmpg highway I was REALLLLLY lucky. And this is exactly what the epa rated my car at. After running the same stretch of highway I've ran countless times, from NY to MD, I got 23mpg with 93octane. City driving, driving the same routes in the same manor resulted in 19-20mpg. There is no placebo in there. So I was curious if there were any similar effects to be had in the h3

 

I had a slight ping with 87 ... gone with 89.

 

Notice any improvements in mileage?

 

Sure, except that putting a higher grade fuel in your engine does not change the timing... which means the compression is the same... which technically means there is no difference in how complete the burn is.

Anyway, aside from that I have had this exact discussion about 50 times over on the Honda forums. Eventally somebody does controlled testing... they end up confirming the mileage is basically the same with regular or premium fuel for engines designed to run on regular fuel.

The last thing to ponder, if GM thought they could claim better MPG just by changing the fuel... they would have.

 

Your wasting your money burning 93 octane in a H3 unless you also have a supercharger, turbocharger, blower or nitrous. Newer computer controlled engines are built to run on lower octane fuels without engine ping. I think the knock sensor compensates the engines timing for the lower octane rating fuels.