@darcyb62: There is no “octane sensor” as such. What you are referring to is the engine knock sensor. If the computer doesn’t detect any preignition (knock) it will advance the ignition timing, which will increase available torque.

@westhighgoalie: If you want to increase CR, you may be able to get a thinner head gasket, or remove the cylinder head(s) and have an engine machine shop remove some material from the face, or disassemble the engine and replace the pistons. A good starting place would be to find an enthusiast website for these motorcycles and inquire there.

But this article is the most useful and informative I’ve yet seen. Nicely done.

I can’t see the logic in using premium for any pushrod engine…but I’m no expert. It’s funny that few seem to buy the mid-grade. It’s either 87 or 93.

On the other side, a Honda Accord is set up to use 87 octane. The environment inside Accord cylinders is not going push that fuel beyond its limits, so it can’t take advantage of the extra resilience of the more expensive brew. It’s added cost with no added advantage. Who wants to waste an extra cent on their fuel?

Honda Accords (at least the one I drive, a 2001 EX) have a knock sensor. I had one replaced under warranty. And YES, it DOES make a noticeable difference in this case. Same goes for my 1988 Grand Prix with knock sensor.

You must be thinking of Sinclair, the company founded by famed oilman Harry Sinclair, who spent six months in prison on contempt of court charges related to the Teapot Dome scandal during the Harding administration. The green dinosaur’s name is, naturally, Dino.

It seems to me that the ethanol in E10 could be considered “the super additive” — surely, nothing will clean your fuel system as well as 10% ethanol in your gasoline, right?

So, if the difference between “Tier 1″ and any other brand of gasoline lies all in the additive packages, then with E10 in the equation, “all bets are off.” Anything with E10 ought to clean the begeesuz out of your fuel system. So, buy the cheapest stuff you can find, and “Don’t worry, be happy.”

Right?

Richfield became Arco which I think is now Exxon.

My favorite gasoline back then was sold in the midwest and had a Dinosaur on the sign.

Last winter they ramped it to regular every other fill-up.

Now they only do premium every third fill-up.

No discerned effect whatsoever in acceleration. No knocking ever, including under heavier load. No change in mpg.

There are lots of internet people who will warn of dire effects, but I would really like to hear their empirical, tested results. The case I’m citing is an actual tested result.

“Octane (a.k.a. 2,2,4 trimethylpentane)”

Should read “iso-Octane (a.k.a. 2,2,4 trimethylpentane)”

(This was already pointed out by a previous psoter.)

If it’s got a proper knock sensor, it should detect and compensate(reduce timing) to handle the lower octane fuel.

“On the other side, a Honda Accord is set up to use 87 octane”

You should hear these cars in the summer time driving up my street(I live on a hill). Ping city. Pretty bad when I can hear it clearly ~50′ away.

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The gas stations are another matter. I guess the fuel truck has compartments for the various octanes? I guess the guy puts the proper fuel in the proper tank at the station?

I wonder how many times they have gotten mixed up? Accidentally put 87 in the 91 tank.

Has some shady station ever filled all their tanks(87/89/91) with only 87 and sold and advertised the other two grades as usual?

Have you ever been to a station that sold five grades(I have)? 87, 88, 89, 90, 91. Insanity. I think the trucks only hold 10,000 gallons. How many separate tanks?

As prices went up, she decided to experiment with lower-octane fuel. She dropped from 93 (Super) to 89 (Plus) with no noticeable impact on performance, economy and no audible pinging from the engine. The drop down to 87-octane (Regular) caused some intermittent issues under part-throttle, low-speed acceleration. So she’s been using 89-octane for the past year or so. It saves about $.15 per gallon.

I wonder if carmakers will work to make all/most of their vehicles compatible with regular unleaded with current fuel prices? A few months back, I was considering an ‘08 Acura TSX until I discovered that it required premium fuel. After visiting a few Acura enthusiast sites, it seems the TSX was not as forgiving as the TL in it’s appetite for premium. =(

They get different gas. Most of the name brand firms get Tier 1 gas while nearly all the discount gas firms get Tier 2.

I would be interested in learning more about gas in the GTA. Do you have any links for further reading? Thanks!

Dinu

That was Sunoco back in the old days. If I remember correctly, they had Sunoco 200 to 260, with the 260 being the 104 octane juice. All the knob did was blend the 200 and 260 grades to get the desired inbetween octance rating out of the hose. Good marketing trick at the time.

I wish I could buy gasoline that was “Guarantted Ethanol Free.” Oh how I wish my motto could be “Corn is for eating!”

night driver: Depending on the engine design, aluminum-headed engines can safely run up to an extra point of CR versus iron-headed engines without having detonation problems.

Overall a very good article IMO. I have a few minor quibbles with it, but other commenters have already pointed them out.

Regarding engines getting “carboned-up”, this became a big problem when MMT and MTBE replaced lead as an octane modifier. Combustion deposits from these chemicals don’t flake off the cylinder head and pistons as deposits from leaded fuel did. I suppose this is one advantage of ethanol being used as an octane modifier.