I run 87 Monday through Thursday, and 91 on the weekends. I commute 750 miles a week. For me, it's a $40 a month difference. Almost a free tank of gas.

 

All cars sold in the US are required to be capable of running 87 octane IAW the EPA regulations. You can run 87 for the whole life of the car if you want, it's not just an "emergency" fuel. Yes, if the knock sensor goes bad you may get knock/detonation, but I can guarantee you'll hear it even with the A/C and radio on. Personally, I didn't run 87 in the C5 unless the chance of running into knock was very close to zero (usually ~Nov 15 thru ~Mar 15 where I live). My ZR-1 has had nothing but 93 octane since I got it no matter when or where I've driven it for no other reason than that's what I wanted to do. Again, it's up to the individual to decide what they want in their car.

If your ABS system fails, you'll lock your tires up in a panic stop and slide right into whatever you were trying to miss...so by your reasoning, you should never do a panic stop in case the ABS system fails. We have a lot of electronic systems on our cars and all of them are susceptible to failure at any time with disastrous results sometimes. I actually had my ABS system "fail" and slid into a bunch of trees (no damage though). I say "fail" because it was as a result of low brake fluid level...when the system sees a "brake warning light" due to low level, it disables the ABS. I learned that one the hard way...don't ever let your brake fluid level get low. I had a failure of my ASR system when I pulled out into traffic once...after it kicked in and stopped a slight amount of wheelspin, it wouldn't give me throttle control back literally leaving me as a sitting duck on a six lane highway. Luckily I had left enough room so I could shut off the engine, restart, and get control back. There are all kinds of "what ifs" in life, you just have to have a little trust sometimes.

PS We have an autocross coming up September 27 in St Augustine...are you going to be there?

 

Hello,

Octane rating of a fuel is the fuels resistance to detonate before the spark plug lites the fuel. The higher the octane the higher the fuels resistance to detonation.

It's a large number of factors that come together that require a higher octane to avoid detonation, examples are: Higher compression engine, more advanced timing, closer to sea level = higher oxygen content of the intake air, higher intake air temperatures = hot outside. Lower octane fuels are fine with, examples are: Lower compression engine, timing retarded more, higher above sea level = lower oxygen content of air intake, lower intake air temperatures = cool outside.

So it's a combination of the above to determine the required octane rating for maximum performance.

On a hot day at sea level with a performance engine you will get poor gas mileage on 87 octane and good performance and gas mileage with 93 octane. But on a cool day at sea level with a performance engine you will get good performance and gas mileage on 87 octane and running 93 octane would be a waste of money. So on and so forth.

Hope this clears up some of the misconceptions.

Douglas in Green Bay

 

My experience with an 05/C6 no mods has been fairly predictable.


Using 91 RON octane/premium (which I usually use), I get between 21-24mpg highway and between 17-19mpg city. Using 89 octane/mid-grade, my mileage numbers are within 1mpg difference for both highway and city. Using 87/regular, I usually get slight pinging (mostly during hard acceleration or full load - passenger, ac, etc.), around 20mpg highway and less than 14mpg city.

Sometimes when I use non-Top Tier (www.toptiergas.com) fuels, my mileage suffers a little bit more (about a 1-2mpg difference). While using TT fuels, the above mpg ratings apply. So I even experience slight variances depending on the type of fuel I use (non-TT versus TT). So that would validate this Top Tier (TT) study somewhat.

An interesting footnote is when I use 76/Conoco (here in No. CA) 91 RON/premium, I get the high-end of mpg and my C6 'feels' a bit more powerful (I wonder if it would dyno-out that way?).

 

What you say is true but I would never recommend that someone put regular gas in their $50k sports car. The fact that it causes the engine to pull timing proves that it's not the best fuel.

Thinking about going to a local autox on the 27th. Have fun at St Aug.