Ive switched from 87 to 89 and have run thru 4 tanks of 89 now. Im going to stick with 89. The vibration in the pedal isn't there any longer. That alone is worth the extra ~$4 a fillup to me

 

Optimum fuel mpg and performance is with mid-grade. The times I've used 87 octane I never get quite the fuel mpg I do on 89.If anything I'd use the 87 once in a blue moon to help clean carbon from valves,pistons etc.Its a hotter/faster burn.That why it spark knocks on 87.

 

Octane History

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.
It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.
During WWI, it was discovered that you can add a chemical called tetraethyl lead (TEL) to gasoline and significantly improve its octane rating above the octane/heptane combination. Cheaper grades of gasoline could be made usable by adding TEL. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:

• Lead clogs a catalytic converter and renders it inoperable within minutes.
• The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).

When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline (known as AvGas), and octane ratings of 100 or more are commonly used in super-high-performance piston airplane engines. In the case of AvGas, 100 is the gasoline's performance rating, not the percentage of actual octane in the gas. The addition of TEL boosts the compression level of the gasoline -- it doesn't add more octane.
Currently engineers are trying to develop airplane engines that can use unleaded gasoline. Jet engines burn kerosene, by the way.

 

http://www.api.org/aboutoilgas/gasol...ine-octane.cfm

Gasoline with a higher heating value (energy content) provides better fuel economy. Traditionally, premium gasoline has had a slightly higher heating value than regular, and, thus, provides slightly better fuel economy, but it is difficult to detect in normal driving. There can be even larger differences in heating value between batches of gasoline from the same refinery, between summer and winter volatility classes, or between brands of gasoline from different refineries because of compositional differences. The differences are small and there is no practical way for the consumer to identify gasoline with a higher-than-average heating value.

 

 

Just so I am clear! I have a 2010 Sport 1500, other then wasting money, is it bad to run on 92 octane instead of 89 ?

 

It would be as waste of money I think to run 92.

As for 87 vs 89, as you can see from my table, despite the higher cost up front, it is the same or cheaper $$ per 100kms driving with 89. So I am sticking with it. Ignore the last tank, a lot of little trips around town at the end of that one, still not too bad though.

 

Predetonation is audible, even in this truck as quiet as it is. Spark knock in other words used to happen to my Durango R/T, I had to run minimum midgrade and since I ran high test a few tanks it started to like it and I was stuck using it after that, I could not get rid of the spark knock without running 90 plus octane, or throw in some octane boost. So don't put anything more than midgrade unless you have a tune that requires it. As far as what happened wow I cannot see it as an issue whatsoever. Just go back to Ctire mid next time. What do you mean they don't have ethanol in their gas? Is this only Ctire cuz I read all the pumps they all have ethanol. hmmmm that is interesting and no ethanol is better for an engine? why? Time for google.

 

What is this 87 and 89 you speak of? I put in 93 But I run a SC 93 tune.

 

So, 92 is good? Won't make the engine run bad?