I changed gas companies

So I find out that one of the local gas stations now get there gas out of Albany, Ny. While all the rest still get there gas from canada. Sooo I decided to change stations and i'm so glad I did. I went back to 87 octane and I was using lucas fuel treatment off an on over the past few months and well on this last fill up I got an amazing 23-mpg around town. I was getting 20 locally and I was real happy with that. But then again the wife has been driving the wagon most of the time so maybe it's just the way I drive? lol but hey 23 is awesome with 235K on it.

Are any of those stations selling ethanol free gas?

There is only one that is about 22 miles away selling ethanol free gas. When I am in that town I always top it off.

It may cost alittle more - but you will notice a MAJOR Gain in performance, and fuel mileage

yeah i hear you and I have noticed it when I get that gas. So worth it.

I have tried several tanks of ethanol free gas with NO improved performance or fuel mileage.

Seriously I think it's our dam right foot that takes away the fuel mileage. Like I said Val has been driving the car for the last fill up and that is what she is getting mileage wise.

on my way up and back from WF10 I got to run through alot of tanks of gas. I could tell when I got the ethanol free as I got 26 vs 23 MPG each time. That was over a vareity of conditions and speeds.

my current OCC with 233K on it, is getting about 22.5 on the highway @80 mph with 3.23s in it. I assume if I could get the cornfree gas it'd go up at least 2.

10% Ethanol cuts mine a couple MPG.
My wifes car gets 40 Mpg on no Ethanol, with 10% Ethanol it gets 35 mpg! worth it!

We have a couple places here who have zero ethanol gas. I put it in all the wagons. It does improve the mileage a bit. But the reason I do it is because the ethanol is really hard on the "rubber" parts the fuel comes in contact with.

DBeaSSt wrote:

We have a couple places here who have zero ethanol gas. I put it in all the wagons. It does improve the mileage a bit. But the reason I do it is because the ethanol is really hard on the "rubber" parts the fuel comes in contact with.

True it KILLS orings & seals - reeks havoc on injectors. If I dont run the ehtanol free fuel I will atleast add a ethanol treatment like lucas has.

hey tim there is one in Horsham on your chart

I think the Ethanol makes everything rust too.......

Run enough fuel through my car, it could be sulfuric acid and it does not sit long enough to do damage.

How about the old moth ball octane boost!

Will do no good for you without the proper program in your PCM.


It is counter intuitive, but octane does not equal more HP. In fact lower octane creates more power. Higher octane prevents engine knock, typically from timing advanced to far. Octane cools the burn of the fuel do you can run higher compression ratio's and more advanced timing. Those are the factors that increase your power.

Article that gives some simple answers............................

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What does "Octane" mean?

Octane is a measure of how much the fuel can be compressed before it spontaneously ignites. When gas ignites due to compression instead of a spark plug's spark, an engine "knock" occurs. By "knock" we mean a literal knocking sound that comes from the engine. Low-grade "regular" gas ignites with the least amount of compression. Higher octane allows gas to compress more than regular which results in more horsepower.

So why aren't we all using higher octane fuels?

Only engines with higher compression ratios take advantage of higher octane gas. These engines are designed this way to increase their horsepower. These are "high performance" engines and cars that have them are the only ones requiring higher octane fuel. These vehicles actually need premium gas and they will perform much better with it.

Octane is thought to give a vehicle additional horsepower by some but the engine's size and design are what makes the car go faster. This performance won't come cheap since premium gas fetches a premium price every time you fill up.

Can you save money using premium instead of regular gas?

You won't benefit from using premium gas in a car designed for regular. You won't get better gas mileage and you won't go any faster. You'll just end up spending more money.

doubt it's true anymore, but in the beginning of the ethanol crap being rammed down our throats, I found 93 would give me that extra 3mpg on highway trips, but about a year or so ago that advantage disappeard. I now assume the 93 was ethanol free for some time but not anymore.

Well then Tim your advice to use plain ole 87 was true after all. Pat yourself on the back from my wagon. But in all seriousness changing gas companies around here might be my best move. A friend of the family told me about a month ago he went and bought some gas and put it in a mason jar to see what it would do,.. and it seperated and he couldn't believe it. Not like the ole gas of yester years.

If an engine requires 87 Octane, that's what it requires and nothing more. The higher octane, if not needed by the engine, can create excessive deposits in the combustion chamber due to an incomplete burn. If you find yourself having to use a higher octane fuel, due to pinging, spark knock or whatever, something is wrong with the engine. It could be running slightly hotter than normal, it may have carbon deposits in the combustion chamber increasing the compression slightly, engine may be running lean, the EGR system could be faulty, etc... Higher octane fuel creates a slower burn of the air/fuel mixture in the cylinder and has a higher ignition point, which prevents this pre-ignition and detonation in the cylinder.

Typically alcohol will have a higher octane rating than most fuels, as does propane and compressed natural gas. Alcohol blended fuels obviously do not burn the same way straight gasoline does. You need more of the blended fuel to do the same work as a straight fuel. This would explain why you get better mileage with unblended, non-alcohol gasoline.

Typically, higher octane fuels will actually harm mileage instead of increase it. Vehicles that use the E85 blend sure don't get good mileage, for the same volume of fuel as straight gasoline. (I think this was done for sticker shock at the gas pump, E85 being cheaper, or at least was at one time.) Put E85 in a engine that doesn't or can't use that type of fuel and the engine management system will set lean fuel trim codes all day long.

1993 Roady-man wrote:

Well then Tim your advice to use plain ole 87 was true after all. Pat yourself on the back from my wagon. But in all seriousness changing gas companies around here might be my best move. A friend of the family told me about a month ago he went and bought some gas and put it in a mason jar to see what it would do,.. and it seperated and he couldn't believe it. Not like the ole gas of yester years.

I said something smart!!! WOOT!!

I think there is some misinformation in the last few posts. In 'olden' days, an engine was set up for a certain octane gas. Today, with the ignition timing having a range of 'adjustment' by the computer through the knock sensor circuit, the engine can adapt and use whatever grade of gas is put into it. You WILL see some power and fuel economy benefit from using better grade gas, but it's not going to be like night and day. IIRC, most owners manuals of fuel injected cars used to state that you should use higher octane gas when towing, to max out power. Today, it's probably not politically correct to state this. More than one engineer has confirmed this info to me. Who is going to be the first to document the economy of their vehicle over several tankfuls of 87 and the same with 93?

I would guess they want you to use higher octane for towing to avoid spark knock when lugging up hills. But just a guess.

With this being said

Quote :

"In 'olden' days, an engine was set up for a certain octane gas."

I agree. So what does determine the octane requirement? Compression is the main ingredient. Compression does not change, with maybe the exception of some experimental engines out there, but for the most part compression is engraved in stone once the engine is built. What does change is the operation of the engine and how it is being used, i.e. towing.

I agree with the fact that if you "push" your engine to its limits and try to get every bit of power from the engine, then, yes an increase in octane may be required. This way the timing can be optimized for "normal" operation while towing.

Quote :

"I would guess they want you to use higher octane for towing to avoid spark knock when lugging up hills."

This is because of the knock sensor system on today's engines. No "spark knock" or "pinging" (higher octane helps prevent the spark knock or pinging) means the ECM can adjust timing to its maximum allowable limit, predetermined through programming and engine operation at the time. Without it, timing would be retarded and therefore reduce engine power. Therefore giving you less fuel mileage because the engine is now being lugged, less than optimum.

But, given the everyday driver that most have here on the forum, I really do not see the benefit of a higher octane fuel being needed. Best I recall, we are talking about everyday driving, and knowing my brother, he is not towing at all with his wagon. The only increase I see is fuel expense at the pump.

Quote :

"Today, with the ignition timing having a range of 'adjustment' by the computer through the knock sensor circuit, the engine can adapt and use whatever grade of gas is put into it."

I can see today's computer adjusting the timing up to a point, to something that is programmed into it, and nothing more. Simply because the programming is not there for any more additional timing, useful or not. Unless, of course, it has been programmed to do so. Programing, from the factory, was optimized for whatever octane they chose at the time of production. Of course there are likely many other factors to consider. Who is to say they are refining and blending the fuel the same way they did when these vehicles were built those many years ago?

Consider this: If the ignition system and other things are not optimized for the higher octane fuel, things can happen. An incomplete burn, for one, will show an excessive amount of fuel in the exhaust stream and the computer will read that as being rich and therefore start to lean out the fuel. Leaning out the fuel then causes cylinder temperatures to rise causing a spark knock. Computer sees this and retards the timing causing some power loss. But as soon as the computer make the adjustment, the oxygen sensor reports a lean condition and therefore the computer increases the injector pulse width adding more fuel to compensate. Computer than sees an opportunity to advance the timing again. Then the oxygen sensor sees a rich exhaust stream again, and starts.... This never ending viscous cycle goes on and on and on, until you turn the engine off.

So... Does higher octane fuel really get you better fuel mileage? Who's willing to give a try, jimbeau?

I don't care about it enough to want to keep track of everything. I'm not copping out; I just haven't EVER cared about fuel economy. My theory has been that if I like my current ride and I can afford the gas, I just fill the tank and not think about it. I never felt it was worth walking around pissed off about my gas mileage. I have a tune & use premium anyway, and my driving is pretty erratic now that I'm retired. I'm not out to prove anything, just relaying info I have been told from the guys who designed these systems for Ford. Compression is a fixed item, but the lowest quality of fuel (octane) that you can use at any given time (within a range) is dependent on how hot the combustion chamber is at any given moment. On a hot day with the engine working hard, there would be more chance for detonation if the fuel used isn't up to snuff. This is the reason for the reverse-flow cooling on the L99-LT1 designs. The heads get coolant first, so they could run the compression up over 10 to 1 and squeeze out more power than they previously could. In any given driving situation, using higher octane fuel will allow the PCM to add more spark advance. This adds more 'oomph' per power stroke, and higher economy would follow. I've always heard that the added economy won't compensate for the increased price of the fuel, but I've never read any conclusive evidence either way. If I recall correctly, when gas was under a buck a gallon, premium fuel was around 10 cents more than 87. Today, how much more is premium? 20 cents? At $3+ per gallon, maybe the increased economy would outweigh the cost difference. Regarding the recommendation to use premium when towing; I was told that it was to make the customer's towing experience better, since the engine would have more grunt, and NOBODY has too much power when towing. It would be great to have some automotive design engineers on line today somewhere, to 'pick their brains'. The ISSF used to have a handful of them, but they are by nature quiet, gentlemanly types, and they threw in the towel there early as the IQ and behavior of the internet went down in the last decade. Oh well... we can still try and hash this stuff out amongst ourselves.

Great conversation and great information. Thanks GMTECH and all others for the input. This IS one reason I spend time on the forum.

OK, so I understand the compression as a requirement for 93 but I'm not sure why we get our PCM's tuned for 93? Does the custom tune add more advance? And if it does, does it add it only when needed... or is the base timing changed?

I am running a 95 PCM in my 96 and have a custom 93 tune. What we have here is "marine mid-grade" or non-ethanol 89 octane gas. Everything else is E-10. I was working on an 89 tune, may have just changed my mind.....

On a stock tune, higher octane will not give you more mileage. It is spec'd for higher octane on tunes to allow more advance.

Krzdimond wrote:

... Does the custom tune add more advance? And if it does, does it add it only when needed... or is the base timing changed?....

As I understand it, there is a built-in 'range' of spark advance adjustment in computer-controlled systems. A range, because for whatever reason, there are limitations, just like there are limitations in any device. On a stock car, the low end of this 'range' is to allow for the engine to function safely on the lowest grade gas available in the most demanding circumstances (towing, etc.). The high end of this operating 'range' is designed to offer the PCM enough leeway in advancing the spark to make the most power the engine is capable of at any given second of time, depending on load, air temp, humidity, etc. Cars have had a mechanical version of this (the vacuum and mechanical advance systems) for scores of years, but it couldn't "think on the fly" because there was no computer to do the thinking. So, if you bought a Chevette, the designers knew you wanted 'cheap', so they made it run on the cheapest fuel grade available. If you bought an Electra or GTO, they knew you were wanting acceleration over 'cheap', so they made it run on the best fuel grade considered widely available, because the higher grade fuel allowed the engine to put out more power than it would using crap-grade fuel. This next point is important to dig: Before computer control, the grade of fuel you used didn't matter or help you at all, as long as it was good enough to avoid detonation. The engine didn't have the ability to adjust beyond the base tune. Today, the computer can allow the engine to make use of a range of fuel grades and split-second conditions that couldn't be dealt with before. I'm old enough to remember when you had to have your carburetor re-jetted when you operated at high altitudes like Denver, CO, because the thinner air made the engine run rich. Part of the flexibility the computer offers to 'adjust on the fly' is that it can make use of better fuel along with adapting to atmospheric conditions. Before computers, cars never ran as efficiently as they were capable of. Today... yup. That's why they all start up (if they are going to) within a few cranks. How many of you here reading this are old enough to remember when you had to 'learn' how to crank your used, piece-of-junk car in the winter so it would start but wouldn't flood?

jayoldschool wrote:

On a stock tune, higher octane will not give you more mileage. It is spec'd for higher octane on tunes to allow more advance.

You can't say this, in absolute terms. The mileage improvement may be miniscule, but the fact that the computer can adjust for conditions means that it can also adjust, or make use of better fuel. All you can state here is that it probably isn't worth the extra coin to do it because of the fuel cost. I will say here that if you make a money bet with a friend over who's car is faster, you would be smart to have the best fuel available in your tank on race day. Then you can go back to saving money on 87 afterwards.

Had a 65 sunbeam alpine that you would crank for a few seconds and then adjust the manual 'choke according to how cold it was.If I got the choke setting exactly right,it
would start up within one turn of the engine.If I got it wrong had to wait and try again.
If I got it REAL wrong out came the plugs and in went the dry set of plugs!Is that old
enough?

jimbeau wrote:

jayoldschool wrote:

On a stock tune, higher octane will not give you more mileage. It is spec'd for higher octane on tunes to allow more advance.

You can't say this, in absolute terms. The mileage improvement may be miniscule, but the fact that the computer can adjust for conditions means that it can also adjust, or make use of better fuel. All you can state here is that it probably isn't worth the extra coin to do it because of the fuel cost. I will say here that if you make a money bet with a friend over who's car is faster, you would be smart to have the best fuel available in your tank on race day. Then you can go back to saving money on 87 afterwards.

May as well invoke the observer effect.

I think you are overstating the capability of the OBD1 LT1 pcm (haven't toyed with OBD2). Sure, some newer cars can adjust very quickly: my folks' Honda Odyssey gets 5hp more if you use premium, and all the 3800 S/C cars I've had have a "bad gas" table built into the PCM. If you use 87 in the SC 3800, it will revert to a "bad gas" table in the PCM with much less timing advance. If you go back to 91, it does NOT instantly revert you back into the "good gas" tables, rather it takes the PCM quite some time to re-learn. In our LT1 cars, if you use insufficient octane gas, the pcm will pull timing if it detects knock. If you have no knock retard using 87, then you're wasting your money using higher octane fuel, both from a mileage and performance perspective even for a "money bet" race.

That being said, I tuned all my PCM for 91 octane because it's easy to find ethanol-free 91 octane here. One of the gas stations that sells ethanol-free 91 refines its gas right here in Canada, and it is discounted every Thursday. The 91 costs less than 3% more than the 87, and I get considerably more than 3% better gas mileage. The increase in mileage justifies the additional cost per litre of the gas. May as well squeeze out the extra 7 hp or so you can get by tuning.

It HAS to adjust quickly. Otherwise, the car would drive you nuts every time you got on or off the throttle, because it wouldn't be advancing or retarding the spark between high & low vacuum conditions.
That said, I guess I'm throwing in the towel, because none of us knows for sure what it's capable of. We offered up our opinions. Back to brotherhood.

supposedly, right before he left office gov Ed "fast eddie" Rendell decreed that for the environment, pa gas stations had to sell ethanol laced fuel. the sonofabich!

oddly enough, my ford focus is a PZEV car..it has to be cause Pa is now a california emissions state! . the PZEV focuses are not flex fuel because E85 is too dirty...wait huh?

on the octane note ford has the turbo ecoboost engines which i believe are the first turbo engines designed to run on regular just fine (high test can be used for optimum performance).
so i guess times are changing.

TiKi seems to run no differently on e10 or e0 so i guess its more of an issue for the TBI cars.