Timing is so retarded on the 5.3 Alpha motor that sometimes it feels like I'm driving a "short bus" instead of a Hummer... better breathing, advanced timing, better exhaust and 93 octane are in my Hummer's future... until then, the 87 octane cheap gas from QuikTrip gets the nod.

 

I use a Superchips Flashpaq. But then again from the sound of yours mine ran better fom the beginning.

 

According to the technical specifications, GM recommends a gasoline posted as 87 or higher for my 2009 Hummer H3 L5-3.7L – no maximum but not less than 87. According to the manual, my H3 can swallow gasolines containing up to 10% of Ethanol but not Ethanol (85%)

Now the big question is: What does the numbers 87, 89 and 93 posted at the pump means?

First, what is Octane?

1 - Methane
2 - Ethane (ethylene, acetylene)
3 - Propane
4 - Butane
5 - Pentane
6 - Hexane
7 - Heptane
8 - Octane
9 - Nonane
10 – Decane

Octane is a hydrocarbon and an alkane that has many structural isomers such the 2,2,4-trimethylpentane (isooctane) that is used as one of the standard values in the “Octane Rating”

Gasoline is a mix made mainly from Octane and some other impurities such Heptane which produces engine’s knock due to its capability of burning very explosively

Of course, is not possible to make more gold by adding cooper but when it comes to gasoline, the “Octane Rating” is pretty much what the consumer want to believe instead of the percent of Octane. To confuse consumers even more, the word "Octane" is used as a short form of "octane rating"

So, what are the numbers posted at the pump?
Generally, in most areas of the world, the Research Octane Number (RON) is used, but in North America, the Anti-Knock Index (AKI) is used so the numbers that you see at the pump are not the percentage of Octane on the mix that you are buying, it is just a number on the Anti-Knock Index (AKI) – GM recommends that number higher than 87 to prevent engine’s knocking.

The average consumers tend to assume that the gasoline numbered as 93 is better and powerful than 83 just because it is more expensive. The true is that in the US, nobody knows what is on the mix.

Let’s assume that 93 is AKI/RdON/PON 91-93 (RON 96–98), then 93 is good for my H3 and it will give me a better MPG than the 87

Unfortunately, that is just an assumption because the pump doesn’t says AKI/RdON/PON 91-93 (RON 96–98), it just say 93 and technically they are not misleading


What about V-Power Racing 100 rated at 100 RON? Well, it can be handled by a NASCAR engine that will cost me a little more than my H3. On my H3, the V-Power Racing 100 can burn the engine

I use V-Power numbered 93 on the pump since December 2009 on my H3 and after 40k miles, my engine runs perfectly and I get a very decent MPG, much better than my sister’s Jeep. I am not sure how many MPG but I drove from Port St Lucie, FL to Miami, FL on just 5 US gallons of V-Power 93

Saving gasoline is good but saving engines is better. The 87 gasoline supposedly contains 87% of Octane + 13 percent of impurities – now add 10% of Ethanol and you end up with “Gasoline 77”

What would be the price that you will be paying for the “Gasoline 77”? Ask your mechanic how much will cost to rebuilt the engine on your Hummer

I don’t know about others because I have been using only V-Power 93 on my H3 and V-Power Diesel on my 2003 F250, I have 40k miles on the H3 that runs as the first day and 150k on my F250 that runs perfectly as new. Also, I have been experiencing a better MPG not only comparing my H3 with a 4.0L Jeep but on others F250s same year, model, weight, tires than my 2003 F250

On the top of all that, GM recommends a gasoline with posted as 87 or higher – no maximum but not less than 87 and stay away from Ethanol and fuel additives other than the ones already mixed on the gasoline

 

I have observed better gas mileage and much better performance over all with Shell gasoline compared to the other top-tier brands.

 

There's a lot to different gasolines and different stations, anyone ever think of when your favorite station had its tanks checked? Or water separators changed? Or even how old the tanks are? All those variables can play a big role in mileage, engine/fuel system longevity, and especially performance

 

You do realize how old this thread is?

 

Yeah sorry, I usually look at stuff when I have down time at work and it's hard to see dates on a smart phone...or I'm just getting old and my eye sight sucks, but we'll go with option 1

 

Last tank I got 16MPG on 87. I assumed I could put that in this truck, I put 93 in my camaro SS of course.

 

Well if you wanna compare numbers, I got this going to Dallas and did the same on the way back to Tulsa today. I wonder what going from 33's to 35's will do...37's? lol