You Next Tank Of Gas May Not Be The Same As Before

[motorguy222]

This is taken from the API site:

"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"

Is It The Same?

 

[Burt]

This is contrary to what I have been told in engineering classes and a class that I took on refinery operations. As I recall, straight, unblended gasoline has 125,000 btu's per gallon but the octane rating is low. To increase the octane, refineries spike gasoline with butane (among other things) which has 103,700 btu's per gallon. Ethanol also raises octane, but lowers btu per gallon big time. The offsetting benefit of higher octane is it allows advancement of the timing and increased compression ratio. So there is some offset to lower btu per gallon. I am told that my 3.5VQ engine from Nissan actually gets more mpg on regular than premium, but I can't say I can tell.

 

[motorguy222]

This is from the American Petroleum Institute,straight from their website.Maybe they are wrong but it is an exact quote from the site.

 

[Shuttler]

May be the case where API person slept through quite a few classes at school. Anyway, they can find enough immigrants educated elsewhere to make it.

 

[LS2JSTS]

I think the paragraph conveys a slightly different meaning when taken in it's full context.....

"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."

 

[Shannow]

Originally Posted By: Burt
This is contrary to what I have been told in engineering classes and a class that I took on refinery operations. As I recall, straight, unblended gasoline has 125,000 btu's per gallon but the octane rating is low. To increase the octane, refineries spike gasoline with butane (among other things) which has 103,700 btu's per gallon. Ethanol also raises octane, but lowers btu per gallon big time. The offsetting benefit of higher octane is it allows advancement of the timing and increased compression ratio. So there is some offset to lower btu per gallon.


Not quite...

Shell have a prodcut down here that's quite expensive, quite high octane, and very energy dense compared to normal premium.

It's using selective cuts to make an energy dense, high octane fuel.

e.g. were you to make a fuel entirely of aromatics, you could have 110plus octane (R+M)/2 with 5% more energy per gallon than regular unleaded.

 

[Ken2]

How precise is the spec for gasoline? Many refineries use crude from different sources, and make different product mixes as market conditions dictate. It is no surprise that there are some variables in the output.

As said above, I don't think any of us could tell the difference without a lab. Several years ago I was talking with a guy from a testing lab. The local refineries buy, sell, and trade product, as all refineries do, and he did the independent lab testing for some of them. When Texaco bought gasoline from ARCO (pre-BP), it was usually below spec. Texaco adjusted the price and re-blended it before they put it out on the market. ARCO accepted this.

 

[mechtech2]

Good luck getting consistent fuel to test this.
We could never know .
Our gains would be far more from possible advanced timing from using the premium.