Various octanes

[yrraljguthrie]

This is more of an information post than a discussion. Hope that is ok? These are not my opinions I am merely repeating known attributes.

Today I discovered gasoline nationwide wholesale costs an average of $2.80 and the national average for retail sale sales is $3.65. Those gasoline retailers are making $.80 per gallon.

87 octane is 87 percent gasoline and 13 percent n-heptane. 89 is 89 percent gasoline and 11 percent n-heptane. This means there is virtually no difference in the cost to produce the various grades.

The n-heptane is to control or regulate the knocking, which today's engine computers can detect and adapt to, which reduces the performance of the engine somewhat.

The difference in performance is only evident at the very top end of the performance. Likely never seen by most drivers.

There can be little to no difference in fuel economy between the various grades, and there is not according to controlled tests. There is a difference when ethanol is mixed in.

Since all gasoline costs about the same to manufacture I wonder who pockets the difference between 87 and 92 octane? Could be $.40 to $.80 per gallon.

I'm never buying anything other than 87 again. Although I would prefer ethanol free. That is a definite difference in mpg and performance.

And my opinion is that RAM is telling us to use 89 so they can advertise 395 hp and 410 foot-pounds of torque instead of a small amount less. I'll settle for say 375 and 400.

 

[SniperDroid]

You have completely disregarded the State and FEDERAL TAX that drives up the gas price. Also the additives that male things cleaner and more efficient. Just saying
.

 

[crash68]

87 octane is 87 percent gasoline and 13 percent n-heptane. 89 is 89 percent gasoline and 11 percent n-heptane. This means there is virtually no difference in the cost to produce the various grades.

The n-heptane is to control or regulate the knocking, which today's engine computers can detect and adapt to, which reduces the performance of the engine somewhat.

um.. no

As quoted from Wikipedia:

n-Heptane is defined as the zero point of the octane rating scale. It is a lighter component in gasoline, burns more explosively, causing engine pre-ignition (knocking) in its pure form, as opposed to octane isomers, which burn more slowly and give less knocking.

100% n-Heptane is actually 0 octane

 

[yrraljguthrie]

Well there is no tax on the wholesale price of gasoline so that figure is correct. I think the $3.65 for retail is before tax, but you could be correct. However, any additives are included in the wholesale cost and mathematically can be factored out. The additives are generally the same in all blends of gasoline by the same brands. Different brands do have different additives. The amount the retail sellers make may be less than I said. The information on blends is completely valid. I never said my information was all-inclusive. I'll stand by the information about different octanes costing virtually the same to produce and about the effect they have on engines, leaving very little reason to buy anything other than 87. Other than the slight increase in top performance.

 

[SniperDroid]

It comes down to what you want, and are willing to pay for. This has been beat to death so many times its painful. When your engine has a tick and you don't know why, now you know why!

 

[yrraljguthrie]

Crash68 what you found on Wikipedia is absolutely correct. That article on Wiki is somewhat confusing. If you do more research you'll find 87 octane is indeed a 87/13 blend of gasoline and heptane. If you think about the wiki article you'll see. Since it's effectively 0 octane less heptane and more gasoline will raise the octane of the gasoline. Pure gasoline is 100 octane. So a blend of 87/13 will get the gasoline to 87 octane. Your quote is correct. um..no is incorrect, or maybe just premature to knowing the entire process.

 

[yrraljguthrie]

I respectfully disagree. While the subject has been beaten to death it has been beaten with a wet noodle and precious few facts. Again respectfully gasoline does not cause tick. Gasoline can cause knock, but the computer is fully capable of eliminating that. And I fail to see why I can't add what controlled tests have shown, rather than what I think. You'll notice I labeled the one "what I think" in my original comment as just that. Using what I read from people who test gasoline, I think there is no reason to buy anything other than 87. You think differently and that's ok. But I don't make the decision on what I can afford, but on what science tells me.

That ticking problem in some 5.7's is likely a problem with the engine that RAM doesn't want to fix or doesn't know how to fix. If it can be stopped with gasoline it may be the additives, the heptane, or the different blends, but is not likely to be the octane itself.