this is what I don't understand about the gasoline debate: originally in 04 or so, Mazda required 87 but RECOMENDED 91+...now it REQUIRES 91+.....did they change the car AT ALL? or just the requirement?? I think that the keeper question right there...because if they changed the car you could make an argument that 91 is necessary, if it is the same car, or even MORE EFFICIENT when it comes to preventing knocking, detonation etc,...then by logic 87-89 should be safe...

 

i wouldn't be surprised if they made an oops kind of mistake,

just like how they messed the omp rate, the spark plugs firing order in early tune, fuel injection rate, etc

 

After I had my car tuned with 100Ron fuel the difference with 95 got pretty consistant. Before that you could only feel a difference during hot summer days.

I wouldn't overthink the fuel choice too much, just use the right octane rating for your car and make sure that the mileage you get out of it is steady.
Fuel chemistry is very complex so it gets hard for us average joes to determine what works best. I tend to use Agip\Eni, Shell or Total fuels here because they're the main distributors (along with Esso\Exxon which sucks) so their stock is always fresh. That's pretty much it.

 

I've found through tuning and general performance(not all on rx's. Mostly FI imports) that Sunoco seems to have the most.consistent octane quality. However shell and BP aren't terrible but have seen cars knock on that gas more times than Sunoco. Just my 2cents

 

what would happen if you filled up half with premium, half with regular...what would that do??

Also I've heard people talk about adding octane booster to their fuel tank. What if you bought regular but added a few drops of that octane boost!?!?

 

You'd get the average of the two. That's how mid-grade works. Gas stations just have two kinds in their tanks: 87 and 93 (or 91 in some states). They mix them proportionally to get 89 or (at some stations in 93 states) 91.

Ken

 

more like they have 2 tanks of gas, 1 is Regular 87 Gas, the other is the god-forbid Ethanol

and they mix them at the pump to raise the octane rating, Alcohol is great at that, just not so great at everything else.

 

Oh, it does prevent gas line freeze in the winter. You don't here about that like you used to 25 yrs ago. It even happened to me once back in the mid-80's. The change to plastic tanks from the rusty metal ones, at the gas stations, probably helps with that too.

 

Other than how ignorant some people are about it the mileage is the only knock against alcohol

 

That would mean 87 has less alcohol than 93. So either regular has less than 10% (violating some state rules and the lobbying efforts of corn growers) or premium has more (violating most auto makers limits). That does not compute.

I always thought octane ratings were obtained with some other additive. Ethanol just lets them use less. And the tanks held either premium or regular.

Ken

 

Higher octanes are obtained from a lighter hydrocarbon thus requiring more cracking, thus making it more expensive. Also why it has more hp, burns easier and cleaner.

 

More cracking is one way. Higher octane used to be done with tetraethyl lead. (Are there any pump jockeys old enough to know what you mean if you say "Fill it with Ethyl?") Amoco did it without lead because they had refineries with the capability of higher refinement. When lead was banned, the majority went to other additives. No idea if Amoco still has their capabilities.

I'll let someone else cover the topic of whether higher octane has more energy or burns cleaner.

Ken

 

Lighter hydrocarbons burn cleaner...period. Ethanol is also a very light alcohol and burns exceptionally clean.

Higher octane actually doesn't have more energy (in fact they have less heating value) it is just easier to combust.

 

BTW Ken, I'm curious, how many miles are you up to?

 

A little over 50,000. Not enough to say whether or not I know what I'm doing about making Zoomy last.

Ken

 

made it over the 100 station today to find they're only open m/f 8-5 GAARGGRRRGGGLLFLLOPPSSS

 

pure gas does make a pretty good difference in the gas mileage and the performance of your car.
Ethanol is "OK" but it does have less btu's than gasoline--hence why it doesnt give you as good of gas mileage. It does have some advantages as Team insinuated, but the trick is that stations dont handle it properly at times ( it really likes water), the percentage is never exactly the same and basically when you use it you are running a duel fuel car. It doesnt make tuning any easier.
There are other ways to increase octane. But, most are impractical for a DD. So tune for what you can get and if you FI dont take the fuel at the pump too casually.

 

i've been using V-power but, just found a place in town that sells 100% gas that I have been thinking about trying out

 

I use shell when I can. Their gas is of good quality, and their 87 grade (which I use) has a higher octane rating than the reported 87 on the pump, and is calculated before the addition of ethanol. That might be true for all companies, but I know for certain that is how shell determines their 87 grade.

 

I switch between shell and sunoco. My butt dyno tells me that the car feels better with the sunoco fuel, but I dunno. It seems to rev smoother after a full tank of Sunoco 93 + premix.

My question is, what effect does premix have when it's mixed with the ethanol and or water which could be in the fuel?

 

call me crazy but i feel the same exact way.

 

in California, we have legislated our own blend of gas, and as such it ALL comes from two refineries, no matter what brand it is.

 

I always, inevitably-- no matter what-- get at least 10% better fuel economy with Shell gasoline than any other, and I'm not exactly some sort of cheerleader for Shell.

A full tank of Shell gasoline (13.5 gallons) typically yields 300 to 310 miles. With competitors, it's consistently 270 to 280.

 

CostCo has been converting its stations to mix additives at the pump at 5x the required limit so one might infer that they are using Shell's additive and they do have a business relationship with Shell in some areas through the sale of Formula Shell oil. I suppose it could be Chevron too as they sell their oils in other areas too. Either way it would be a win win and I doubt they doing anything otherwise given the ease of sourcing the additive.