Costco Gasoline

[427435]

This is a highly complex issue and I provided a very baseline answer. There are many reasons for a gasoline engine to knock and as many ways to reduce or prevent it. But the basic reality is that the combustion chamber designer does not want ignition of the compressed gasses inside the chamber to proceed the flame front. Doing so will cause the ping, or knock. Therefore, reducing the burn, or spread, of the flame front timing tends to reduce the chances of knocking. This is what I meant by "slower burning".

We are discussing knocking in passenger car engines under normal use. Racing applications are something else entirely. The same basic principles apply, however, more solutions are available to a racing engine designer due to removal of cost constraints and availability of exotic fuels.

Yes, it is a complex issue. However, the primary difference between regular and premium fuel isn't flame front speed. High compression engines are often higher rpm engines (both are good for more hp). If anything, as rpm goes up, a faster flame speed is desired.

The major difference between regular and premium gas is the chemical makeup of premium gas (including additives) requires a higher combination of pressure and temperature before it auto-ignites----------not a slower flame speed.


Or as Click and Clack (a couple of MIT graduates) put it:


Q. How does high-octane gas help?


A. Compared to regular gas, high-octane gas requires higher temperature and pressure to ignite, so it can withstand higher compression without reigniting. As such, it's less likely to result in premature ignition, and therefore prevents pinging and/or knocking.

In other words, it's a form of protection for high compression engines.


http://www.cartalk.com/content/premium-vs-regular-1

 

[landtuna]

Or as Click and Clack (a couple of MIT graduates) put it:

Hey, I love Click & Clack (The Tappet Brothers) but I find it very difficult to trust the opinions of people who drive a 1963 Dodge Dart.

 

[dg_moore]

Hey, I love Click & Clack (The Tappet Brothers) but I find it very difficult to trust the opinions of people who drive a 1963 Dodge Dart.

They have written up their experience with the Dart thoughtfully and in considerable detail here:
http://www.cartalk.com/content/1963-dodge-dart-convertible (take particular note of the antipenultimate paragraph).
If they can quote Sartre in an automobile review, then aren't their opinions worth at least acknowledging?

 

[Mark_888]

They have written up their experience with the Dart thoughtfully and in considerable detail here:
http://www.cartalk.com/content/1963-dodge-dart-convertible (take particular note of the antipenultimate paragraph).
If they can quote Sartre in an automobile review, then aren't their opinions worth at least acknowledging?

Click and Clack only says things they think are funny, and any relationship to the truth is strictly accidental.

 

[EXBMWGUY]

Click and Clack only says things they think are funny, and any relationship to the truth is strictly accidental.

The fact that humor is an integral part of their brand does not, in itself, reflect on their knowledge. They have been accused of being out of date with the latest car technology, but that is unfair in view of their target audience who rarely knows the difference between 2-cycle and 4-cycle engines and thinks brake fluid and power steering fluid come out of the same bottle.

 

[dg_moore]

The fact that humor is an integral part of their brand does not, in itself, reflect on their knowledge. They have been accused of being out of date with the latest car technology, but that is unfair in view of their target audience who rarely knows the difference between 2-cycle and 4-cycle engines and thinks brake fluid and power steering fluid come out of the same bottle.

...and, according to this weekend's broadcast, motor oil, at least in the Phillippines.

 

[videopho]

My 800 miles recent road trip features relatively and mostly on flat terrain (I-95 Mid Atlantic/NC/VA/MD region) with ~ 780 miles driven with highway speed (70+) and the rest was well below.
Weather wasn't any factor either way or insignificant. i.e. wind direction/wetness etc.
The out bound trip, I used BP 93 octane, average 25 mpg
The trip home, I used Costco 93 octane. average 25 mpg
There virtually seems to be no advantages/disadvantages here, between top tier quality or not which is expected. (BP is not top tier, is it?)
My next experiment: in a long trip like this, I will consider using Ethanol free gasoline 93 which is plentiful here in Eastern NC in one direction vs Ethanol gas the other.