Premium gar vs. regular: What's really better for your car?

[Killramos]

I think the biggest problem with people misunderstanding octane ratings is the fact that they call them Regular, Mid Grade, and Premium.

91 octane gas isn't necessarily better. Its different.

When people hear the term "premium" they assume its better. And the gas companies make it worse by saying ( which may or may not be true) that the Premium gas has better additives for your engine in addition to the octane difference.

If they just refered to the different fuels exclusively by octane rating it would be less confusing i think.

Another hilarious think i have noticed is some shell stations now have Diesel V Power

[MightyMouseTech]

Originally Posted by Killramos

Another hilarious think i have noticed is some shell stations now have Diesel V Power

Why? It has a higher cetane rating, just like having a higher octane rating. My smart was tuned to run on higher cetane. Although, it is completely done by additive. The regular diesel did not get any of the additive, the higher cetane fuel was just the regular with the additive added. You could actually see the additive lines on the pump.

Was surprised when I pulled up to a pump in Italy, only one grade of gas, and three grades of diesel.

[Nitrousbird]

Originally Posted by wdb

Most cars built in the past 10-15 years have knock sensors, little gadgets bolted to the block that will pick up knock and send a signal to the control computer. They're capable of detecting knock long before human ears ever hear it. Which is not to say that you will never hear it, after all the computer has to act on the signal, and how/when it does that will determine whether a human will hear an engine knocking.

In short: no, the lowest octane that does not produce audible knock is not the correct one for your car. The correct octane for your car is the one the engineers who designed the engine and control systems tell you to use.

Where did I ever say audible knock? I very specifically stated knock occurrences, which is what the knock sensor picks up.

Engineers also have to cover a wide variety of fuel/conditions, EPA regulations and a number of other factors that have nothing to do with knock. The correct answer, again, is the lowest octane that doesn't create a knock occurrences / timing to be pulled. A few logs of varying conditions (low RPM/high load, WOT to redline runs, etc.) can let you know where you need to be.

[RM7]

Originally Posted by Railgun

That's a horrible analogy.

Well, his analogy with beer was pretty spot on for me. I don't drink the beer-inspired rice-beverage that is marketed by the big beer companies, because I enjoy beer. If I want to cool off and quench my thirst, I drink water. If I want a nice beer, I get a Trappist or nice barrel-aged beer, every once and a while an IPA. They cost more, but I'm not going to drink a bud light to save a few dollars, it's not worth it in the end. Maybe a better comparison is nice Scotch. A nice Scotch is not cut with sugar like cheap Whiskey and other alcoholic beverages. That sugar and the additives they put in there to make them simulate more expensive stuff give you a nasty headache. It's never worth it.

I've had 3 high octane/high compression cars. It's what they like. It's good for them. It's what they were designed for.