Fuel quality

[rattroddrebel]

Hello,
I am new my name is JP, new to ecomodder but no stranger to modifying anything for fuel gains or HP increase. Part of my ideas for wanting to be a member here is sharing as much information as possible with everyone because I am an ASE certified mechanic, but wanted to be a scientist for as long as I can remember. The problem is some vehicles are limited to how much economy they can get. I get asked everyday how people can improve mileage, and all of them drive V8's!!! I was getting a part at Oreilly one time and there was this huge biker dude asking this young kid at the counter what he could buy to get better gas mileage on his 1 ton Dodge v-10! I wasnt the one he was talking to but I popped off with "you could save alot of money buying a 4 cylinder". Lets just say I was lucky I didn't get punched.
Anyways My topic for discussion is fuel quality, has anyone experimented with trying gas from every gas station in their area and comparing the economies between them? I have done this and In my area fuel is $3.11 per gallon right now, I normally buy Shell gasoline because my mileage is awesome, I dropped 10mpg using Casey's 10% ethanol, its just crap.

[mackerel]

My mechanic says that over the last 10 years, gas quality has gone way down hill, to the point where some gas is hard to light with a match. (I haven't tried that myself).

It's a good question, but I think you'd need a bunch of people to all sign on and fill at the assigned station, then after a month or so, switch the control and experimental groups. Otherwise, between weather and variation in the types of trips people run, there'd be too much statistical noise.

You'd also need to compute miles per dollar, seeing as how the cheap stuff is, well, cheaper, even if slightly lower quality.

[Daox]

It would be interesting to hear from someone actually in the field who knows what they're talking about. I've heard similar stories from mechanics and other people who claim gas is junk now-a-days. However, its clear these people aren't doing any form of gasoline testing to see what is good/bad. Its simply what they think, or have heard from others. Perhaps it really is bad, or maybe its just the engines they work on. Who really knows unless you actually do controlled testing.

[Weather Spotter]

well the octane rating is a standard test and by law in most states the gas sold as 87% must have a performance equal to the rating. Octane is a measure of how many Carbon molecules are attached to the H molecule. the C-H bond is what stores the energy in gas. Heptane (7 C's) was assigned a value of 0 and (8 C's) was assigned a value 100. so a gas rated at 87 would perform as if it were 87% Octane and 13% Heptane. it never is actually that mix but is a blend of CH chains in that range.

since the C-H bond stores the power the only thing that can change is the additives but they do not change the amount of raw energy in a volume of gas. it might effect how the gas vaporizes or how clean it burns but the Octane rating insures the same minimum number of C-H bonds are available to be broken and turned into useable energy.