Premium Octane?

[Big TP]

Does it matter or is it worth it to use Premium?

[53driver]

Does it matter or is it worth it to use Premium?

My owner's manual says "86 or better."
My experience is that I get better gas mileage with 87.
I live nearer sea level and when I ride in the foothills/mountains (up to 4000' or so) I notice no difference.
Those in Colorado may have different experiences WRT pinging and octane.
Cheers,
Steve

[tenxxx]

Depends on how the bike is running on what you have been using.
I would say 89 at the least. I get a little drop in milage with 87 which is around 85 octane equivalent with ethanol mix.
They don't use the same formula to get octane rating with ethanol blends.
So if your using the blend your guess is good as mine.
I avoid the "Blends" when ever possible. Only a few places left to get the good stuff any more.

[Kokomo Kevin]

I have run Octane boost in my Legacy Valk for years due to Ignition set to performance settings, I do occasionally put in Lucas octane boost into the B as well. I think it helps it at times. I think it is due to blended gas as well, sometimes the blend is on the low side. Not pushing it, but you might try and experiment with it in a few tanks to see what you think....
You think blended gas is bad now? Wait till the "new" and improved blends come out in a few years!

[olegoat345]

I think my bike calls for 89 or above. I just started using 90. Might be a tad better on take off.

[VStarRider]

One of the main selling points for me on the Honda was that it runs well even on piss and vinegar.

I never use anything but 87, except in the pre-storage season (now), and I get a steady 42 mpg with no pinging.

Gas. Oil. Tires. Fuel stabilizer. Seats. Spouses. We each have different tastes, and become loyal to those that we have positive experiences with.

[bob109]

One of the main selling points for me on the Honda was that it runs well even on piss and vinegar.

I never use anything but 87, except in the pre-storage season (now), and I get a steady 42 mpg with no pinging.

Gas. Oil. Tires. Fuel stabilizer. Seats. Spouses. We each have different tastes, and become loyal to those that we have positive experiences with.

+1 on the use of regular! Why pi$$ money away on High Test when our motors are equipped with 3D Mapping, Oxygen and Crank Sensor and the likes. Honda did a remarkable job in designing the "Boxer Flat Six". Fuel requirements are clearly spelled out in the Owners Manual, as is oil change intervals which no one seems to follow. With 57K miles on my 13, its never seen a drop of High Test. I routinely use Sea Foam and the original OEM spark plugs are still in place with 40/42 MPG. Of course all of us has a "personal preference" which makes us feel "warm and fuzzy"! If High Octane gives you peace of mind, so be it!

[2wheelsforme]

Octane is a measurement of the gasolines resistance to knock or ping also known as pre-ignition. It is not better or higher quality fuel. If your engine does not knock or ping with 87 then you are wasting money running a more expensive higher octane fuel. Nor will using a high octane gas give your bike better mileage. That's because the rating refers to how much energy it takes to ignite the gas, (slower ignition equals less pre-ignition) not directly to how much energy the gas puts out.

[opas ride]

Octane is a measurement of the gasolines resistance to knock or ping also known as pre-ignition. It is not better or higher quality fuel. If your engine does not knock or ping with 87 then you are wasting money running a more expensive higher octane fuel. Nor will using a high octane gas give your bike better mileage. That's because the rating refers to how much energy it takes to ignite the gas, (slower ignition equals less pre-ignition) not directly to how much energy the gas puts out.


As I have said on many earlier posts regarding this issue...using higher octane fuels just cause one thinks there going to make some noticeable difference in mileage or performance, is just like "pissing money down at rat hole" !!!...No need at all unless you like to spend extra $$ on gas for your bike....Regards and ride safe

[Kokomo Kevin]

Just for Sh_its and giggles has anyone ever used aviation gas or racing gas in a B?

[tpwood]

+1 on the use of regular! Why pi$$ money away on High Test when our motors are equipped with 3D Mapping, Oxygen and Crank Sensor and the likes. Honda did a remarkable job in designing the "Boxer Flat Six". Fuel requirements are clearly spelled out in the Owners Manual, as is oil change intervals which no one seems to follow. With 57K miles on my 13, its never seen a drop of High Test. I routinely use Sea Foam and the original OEM spark plugs are still in place with 40/42 MPG. Of course all of us has a "personal preference" which makes us feel "warm and fuzzy"! If High Octane gives you peace of mind, so be it!

+2, it's not like back in the 70's and 80's, the new ECU's on vehicles takes care of all that, if your not pinging don't change use what's recommended, even Consumers Report says the same thing.

[ReserveBum]

Octane is a measurement of the gasolines resistance to knock or ping also known as pre-ignition. It is not better or higher quality fuel. If your engine does not knock or ping with 87 then you are wasting money running a more expensive higher octane fuel. Nor will using a high octane gas give your bike better mileage. That's because the rating refers to how much energy it takes to ignite the gas, (slower ignition equals less pre-ignition) not directly to how much energy the gas puts out.
Have to disagree here. I use mostly 87 and get the standard 40-42. We have a place here that still sells "91 ethanol free", when I use that I get 43-45 mpg. I believe it also runs a little smoother on take offs. During this years rally, when we were in CO, we were getting 50 on some runs, but drop some elevation and get into Kansas, the mpg's dropped into the 30's

[2wheelsforme]

Have to disagree here. I use mostly 87 and get the standard 40-42. We have a place here that still sells "91 ethanol free", when I use that I get 43-45 mpg. I believe it also runs a little smoother on take offs. During this years rally, when we were in CO, we were getting 50 on some runs, but drop some elevation and get into Kansas, the mpg's dropped into the 30's

Talking about octane, not ethanol vrs pure gas. I agree pure gas what we call here marine gas is better, and much more expensive. Two other things that affect the possibility of pre-ignition are timing advanced motors and high altitude. In other words it is the pure gas causing your better mileage not the octane. I also got better gas mileage while in high altitudes' this summer.

[F6Dave]

As has been stated, using gasoline with more octane than your engine needs is a waste of money. A higher octane rating means the fuel is more resistant to detonation or pinging. In general, engines with higher compression are more prone to detonation. Other factors, like combustion chamber shape, ignition advance, and temperature are also contributing factors. Higher octane keeps the problem under control.

Once you choose a fuel with a high enough octane rating to prevent detonation, absolutely nothing is gained by using a higher octane rating. In fact, higher octane fuels actually have slightly less energy content, so using them unnecessarily could actually decrease performance and mileage by a tiny (probably not measureable) amount.

There's another factor at play. Modern vehicles have engine management computers that adjust for detonation, allowing lower than optimum grade fuels to be used without causing engine damage. Knock sensors tell the computers to adjust ignition timing. So it can be difficult to tell if your engine could use a higher octane fuel.

My personal experience with my 2 old Valkyries and 2 F6Bs has been interesting. My '98 Valkyrie Tourer runs great on any fuel, even the 85 octane junk they sell at high altitudes. In 175,00 miles I've never detected any pinging whatsoever. However, my '99 Interstate pings badly on hot days when accelerating hard with regular fuel. This could be because Honda used an ignition control module with more advance on the Interstates to compensate for the added weight. In the summer I always use mid grade or premium on that bike.

My F6B experiences have been more surprising. I had a 2013 that often needed premium fuel. I had been running 87 octane ('mid grade' at high altitudes) and on a hot day, I heard some brief pinging when accelerating. It quickly disappeared, then returned, then disappeared again, so the computer must have detected it and made timing adjustments to compensate. After that I began using 91 octane whenever the weather was warm. On the other hand, my current 2016 has no problem at all with 87 octane fuel.

I have no idea why the 2013 was so picky. Maybe I had an unusual bike that was slightly out of spec, or maybe Honda upped the power on those early F6Bs. That's happened before, as the '97 Valkyries performed better than subsequent years.

[Kokomo Kevin]

Dave, Thanks for your information. I too have a 98 Tourer with Dyna 3000 ignition set to 7 degrees advanced and the Rev limiter turned off. Although I never run it THAT hard it needs to have Octane to prevent pre ignition problems. It is a very strong runner. I have experimented a little on my 13 F6B as well, just seeing if I notice any difference and I believe I do see some improvements in drive ability performance etc. with Octane boost. I think it just counteracts with all the grain alcohol gas we have here in the midwest. Wish I could find a source that did not have it. Not looking forward to the future , as they are forcing higher % of grain based fuels.

[F6Dave]

Dave, Thanks for your information. I too have a 98 Tourer with Dyna 3000 ignition set to 7 degrees advanced and the Rev limiter turned off. Although I never run it THAT hard it needs to have Octane to prevent pre ignition problems. It is a very strong runner. I have experimented a little on my 13 F6B as well, just seeing if I notice any difference and I believe I do see some improvements in drive ability performance etc. with Octane boost. I think it just counteracts with all the grain alcohol gas we have here in the midwest. Wish I could find a source that did not have it. Not looking forward to the future , as they are forcing higher % of grain based fuels.

I was thrilled when a Murphy Express station opened near my house recently. It sells mid grade 'pure gas' for a little more than their price for the ethanol stuff.

[tenxxx]

High octane gas burns slower and cooler. Dip a finger in 87 octane and blow on it. Its gone in a few seconds.
It burns the same way. Fast and furious. It takes less heat to ignite it.
Sometimes just a hot spark plug tip and a little compression will set it off before it time. Spark Knock.
The compression ratio on the B is low enough to burn 87 ok. But it is borderline. Some bikes with a few tenths higher compression may knock on 85-87.
If you have the knock, higher octane will cure it.
I never run less than 89 in anything. They say you can run 85-87 cause the ECU can hear it and adjust the timing.
To me that means there will be knock on the lower octane. We'll just let the computer handle it.
Nothing wrong with that I guess. Its been that way for MILLIONS of miles on Goldwings, and no problems to speak of.
I believe its just easier on the engine to run a better grade of gas.
We all look for the best oil, why not gas.
Its all a matter of opinion. And this is mine.

[2wheelsforme]

I thought it was understood that higher octane gas is not better gas than lower octane. You should use the one specified for your engine or go up if you suffer from ping or knock.

[Big TP]

I thought it was understood that higher octane gas is not better gas than lower octane. You should use the one specified for your engine or go up if you suffer from ping or knock.

Well I have not had any issues with the 87 octane, it just so happened that the when I accidentally filled up last time with 92, it "seemed" more responsive.

Placebo??

[Kokomo Kevin]

I think that given Honda's tight specs in engine mapping, what we are seeing is more to do with fuel quality. I do think there are some differences, obviously in the blends, but we all need to consider that there is most likely vast differences between storage at stations. I believe moisture content is probably causing some variance. I usually fill up at HIGH volume stations in my hometown. I have in the past gotten what I think is bad gasoline. In those cases I did notice a difference in the way my vehicles ran. Good discussion! Anyone have any other bad fuel stories?

[2wheelsforme]

Placebo? Certainly possible. Bigger difference in the way a station handles fuel than in what kind of fuel is also certainly possible as well as water in the mix. High volume stations are what I look for also. I also do not fuel when a tanker truck is refueling the stations tank. That process has to be disrupting the sediment on the bottom of the tank and putting into the pumps. Dispelling the myth of more expensive high octane gas is better gas is a tough one to squash. The labeling has some to do with it I think, with the regular vers premium thing. Google or Bing octane and you can read a ton of stuff with almost everyone agreeing no benefit to hi-test if your engine does not need it.

[Az Wingrider]

2wheelsforme has pretty well summed up my feelings as well. I use 87 octane almost exclusively. In areas with lower octane ratings (85 or 86) I use a mid range grade of fuel. I also will not use a station that is getting a fuel delivery because when they are dumping fuel it stirs up all the crap in the bottom of the tanks. I also avoid stations that do not seem to pump a high volume of fuel. I do quite a bit of riding in northern Arizona on the Navajo Reservation and I have gotten bad fuel there but for the most part the Hondas I have owned have all been pretty forgiving on the quality of fuel I put in them.

Good discussion
Az wingrider

[6gun]

I believe if 87 octane works for your bike and makes you happy, why spend more money. If your goal is to get every bit of performance from your bike, you may benefit from higher octane. If the engine management is managing knock, it is adjusting timing advance. This will have an affect on acceleration. Not sure how many of us can measure the difference with the seat of our pants. But there will be some difference.

[2wheelsforme]

No, an engine designed to operate on 87 will not benefit from higher octane. https://www.scientificamerican.com/article/fact-or-fiction-premium-g/

[Big TP]

No, an engine designed to operate on 87 will not benefit from higher octane. https://www.scientificamerican.com/article/fact-or-fiction-premium-g/

Thanks Mike. That is pretty much the consensus. 87 from now on.

[ckwizard]

Owners manual says 89 or higher so I run 92 all the time.

[6gun]

That is a very simple explanation of engine vs fuel design. That is why I said, if it works for you be happy. They left some details out. For most, the details will never matter.

[1951vbs]

In the 118,000 miles I have collectively put on my 2013 & 2015 F6B's I have saved $1242 by using 87 octane.
I did quite a bit of dyno testing years ago and learned my lesson then. If your engine doesn't have enough compression and/or ignition advance to burn higher octane it will actually detract from the performance. Higher octane fuels are made to control detonation and will burn slower.

[2wheelsforme]

Owners manual says 89 or higher so I run 92 all the time.

And the myth lives on! Wondering where you got that info about the manual saying "89 or higher"? My manual says 86! Someone earlier said something about aviation fuel and I think fuel for planes is still leaded and lead is a do not use warning for our bikes.

[opas ride]

Owners manual says 89 or higher so I run 92 all the time.

I have never seen any such octane instructions in any Honda F6B manuals..."Show me the money" so to speak....Regards and ride safe

[53driver]

My 2014 Owner's Manual, page 136, states "86 or above"

I'm finding it fascinating that there are other Owner's Manuals stating differently.
Here is a snap from my manual - not something downloaded off the 'net.

If your Manual states different than mine, please post a pic and the year of your bike. This could be very interesting.
Cheers,
Steve


I have never seen any such octane instructions in any Honda F6B manuals..."Show me the money" so to speak....Regards and ride safe
They are there, my friend!

[3Chief]

I run Chevron 91 almost exclusively. I don't much care what our manuals say as my piece of mind is preserved by running higher grades of fuel. I stick with Chevron for consistency/quality.

[2wheelsforme]

My manual for a 15 is the same as Steve's, 86. The myth: Higher octane rating equals higher grade of gas. Most people who know more than me agree that is not true but is still appears to be a belief of many.

[53driver]

My 2014 Owner's Manual, page 136, states "86 or above"


I run Chevron 91 almost exclusively. I don't much care what our manuals say as my piece of mind is preserved by running higher grades of fuel. I stick with Chevron for consistency/quality.

91 'above' 86
So, you're good!

Cheers,
Steve

[Big TP]

Does it matter or is it worth it to use Premium?

Well I guess the answers provided to my original question is......:confused:

Maybe a better way to ask the question is... Is it worth the extra 30 - 60 cents a gallon? Seems YES only if you have a performance issue (knocking, pinging) or if it makes you FEEL better.

[3Chief]

My manual for a 15 is the same as Steve's, 86. The myth: Higher octane rating equals higher grade of gas. Most people who know more than me agree that is not true but is still appears to be a belief of many.

Honestly it may not matter on most newer fuel injected vehicles, however my personal experience has been better performance with higher octane ratings on my older vehicles. I'm more brand specific for the same reason as I've had issues with many of the off brand fuels. Mostly your paying for the additives at this point. If I remember correctly most fuels are mixed from the same base gas, only a few suppliers own the whole chain. Amaco was one of them. I've gotten the best/most consistent performance from Chevron and Conoco. Conoco's are few and far between on the West Cost so Chevron is my station of choice. The extra price is worth it to me for the piece of mind it brings. Just my .02...or .25 if I'm at the pump :cheers:

[VStarRider]

Well, if you use 91, enjoy. I'll keep the $$ difference and use it to pay for more accessories until my bike looks like Pee Wee Herman's.

[ReserveBum]

Well, if you use 91, enjoy. I'll keep the $$ difference and use it to pay for more accessories until my bike looks like Pee Wee Herman's.

Its not what you think.....this mornings price at my local store: $2.93 for 87 octane unleaded and $3.47 for 91 octane ethanol free premium. If you do the math and use a 6 gallon fill up, it will cost you $17.58 for regular and $20.82 for premium. If I get 41 mpg on unleaded, I'll get a 246 mile ride for my 6 gallons. For the same 6 gallons, I'll get 264 miles at 44 mpg for the premium. Break it down to the per mile fuel cost and it costs me $0.1399 per mile for unleaded and $0.1268 per mile for premium so.....Its cheaper for me to run the premium, get better mileage and what I perceive as better performance.

[2wheelsforme]

Yes that ethanol free fuel is better. Much more per gallon than mix in this part of the world but better. I run it in lawnmower, chain saw, generator and boat.

[F6Dave]

When it comes to mileage, what matters is how much energy is in the fuel you use. Here are a few numbers:

Diesel #2: 129,500 BTU/gal
Regular gasoline: 114,100 BTU/gal
E10 gasoline: 111,836 BTU/gal
E85 ethanol: 81,800 BTU/gal
Pure ethanol: 76,100 BTU/gal

The numbers say that ethanol free regular (87 octane) gasoline has about 2% more energy than an E10 blend. So you should see roughly a 2% improvement in mileage by switching from E10 to pure gasoline. That's less than 1 MPG in my case, and given the normal variations in my mileage I haven't really noticed a difference.

BTW, 91 octane premium actually has slightly less energy content than 87.

[Big TP]

Its not what you think.....this mornings price at my local store: $2.93 for 87 octane unleaded and $3.47 for 91 octane ethanol free premium. If you do the math and use a 6 gallon fill up, it will cost you $17.58 for regular and $20.82 for premium. If I get 41 mpg on unleaded, I'll get a 246 mile ride for my 6 gallons. For the same 6 gallons, I'll get 264 miles at 44 mpg for the premium. Break it down to the per mile fuel cost and it costs me $0.1399 per mile for unleaded and $0.1268 per mile for premium so.....Its cheaper for me to run the premium, get better mileage and what I perceive as better performance.

I may be wrong but looking at your numbers it seems you spent $.3.24 more on the Premium fill up and got 18 more miles?
If that's right than the 87 octane would be cost efficient, of course not taking into account perceived performance improvements.
Most Respectfully,
TP

[3Chief]

When it comes to mileage, what matters is how much energy is in the fuel you use. Here are a few numbers:

Diesel #2: 129,500 BTU/gal
Regular gasoline: 114,100 BTU/gal
E10 gasoline: 111,836 BTU/gal
E85 ethanol: 81,800 BTU/gal
Pure ethanol: 76,100 BTU/gal

The numbers say that ethanol free regular (87 octane) gasoline has about 2% more energy than an E10 blend. So you should see roughly a 2% improvement in mileage by switching from E10 to pure gasoline. That's less than 1 MPG in my case, and given the normal variations in my mileage I haven't really noticed a difference.

BTW, 91 octane premium actually has slightly less energy content than 87.

Information like this that people post is one of the things I love about this board. I'm continually amazed and further educated by the knowledge that is shared here.

[tenxxx]

When it comes to mileage, what matters is how much energy is in the fuel you use. Here are a few numbers:

Diesel #2: 129,500 BTU/gal
Regular gasoline: 114,100 BTU/gal
E10 gasoline: 111,836 BTU/gal
E85 ethanol: 81,800 BTU/gal
Pure ethanol: 76,100 BTU/gal

The numbers say that ethanol free regular (87 octane) gasoline has about 2% more energy than an E10 blend. So you should see roughly a 2% improvement in mileage by switching from E10 to pure gasoline. That's less than 1 MPG in my case, and given the normal variations in my mileage I haven't really noticed a difference.

BTW, 91 octane premium actually has slightly less energy content than 87.

Why do drag racers use high octane?

Its all about the conversation.
Many different ways to justify your reasoning.
Many informative ideas and opinions.
Thank GoD for giving us all different perspectives on things.
A good thread where theres no, I'm right and your wrong.
What ever makes you Happy, Happy, Happy,,,,,,

[Kokomo Kevin]

Amen brother! If you didn't know you do now, if you didn't care you might now. Nothing like a damn good conversation, winters coming probably going to have few more before next spring....

[VStarRider]

I totally agree. I am on several forums with snowmobiles, another motorcycle forum (Star Bike Forums) with a few know-it-alls who dominate every thread, and often name calling is breaking out before the first page is filled with posts. Though Doo Talk (Ski Doo snowmobiles) is pretty good as well, probably a close second to this forum. I am in the middle of a discussion now on the decline of snowmobiling, very interesting. There are a lot of parallels between snowmobiling and motorcycling.

Anyway, I always enjoy the conversation and never respond with the thinking that I am going to change someone's mind. Just talking.

Things on my bike that probably would not be there without guidance from this forum:

Ragestad, Baker Wings, fog lights, and the biggest - doing all the maintenance myself!!!

For the record, I use:
Mobil 1 Racing T 10W 40 oil
Honda oil filters
87 octane gas
8,000-10,000 mile oil change intervals
Exedra tires
Pro Honda "Pledge" spray
Corbin seat

[F6Dave]

There's one more thing worth mentioning. A higher octane fuel than your engine needs can't hurt anything, but too low an octane can cause serious engine damage. So on older engines without engine management computers and knock sensors, it's safer to err on the side of more octane.

[Big TP]

91 'above' 86
So, you're good!

Cheers,
Steve

Yes Sir, Like the book sez, 86 or above . So 87 is what I will be staying with until otherwise necessary.

[1951vbs]

Its not what you think.....this mornings price at my local store: $2.93 for 87 octane unleaded and $3.47 for 91 octane ethanol free premium. If you do the math and use a 6 gallon fill up, it will cost you $17.58 for regular and $20.82 for premium. If I get 41 mpg on unleaded, I'll get a 246 mile ride for my 6 gallons. For the same 6 gallons, I'll get 264 miles at 44 mpg for the premium. Break it down to the per mile fuel cost and it costs me $0.1399 per mile for unleaded and $0.1268 per mile for premium so.....Its cheaper for me to run the premium, get better mileage and what I perceive as better performance.

Not sure your math is right...From your figures I calculate $.0715/mile on regular $.0789/mile on premium

[BIGLRY]

One thing I have not seen mention when talking about Octane numbers is the additives used by manufactures. You will find more additives in 97 Octane than in 87 Octane used for cleaning the engine's fuel system and help cut down bad emissions, but here is the rub. I have found engines that are designed to run on 87 Octane but are feed a steady diet of 97 Octane will have more deposits on the spark plugs over time due to the additives.

Is true there is technically more energy in 87 Octane than 97 Octane as the 97 is designed to burn slower in the higher compression engine. Even in the low compression engine say 9:1 if you put on a Turbo or a Supercharger you must run the higher octane if you are running boost and if you have a turbo Or Supercharger who don't twist up the wick once and a while?

All I'm saying is if you run high Octane fuel for feed for the steed then keep an eye on the spark plugs for crud build up and I'm talking about long time use.

https://www.jackssmallengines.com/diy/wp-content/uploads/2015/03/read-spark-plug.jpg

[Kokomo Kevin]

Good info Larry, As usual. You are the King of Technical on this website, lest anyone else not think that!

[Big TP]

And with visual aids!!!'all/right'
Love it.

[F6Dave]

One thing I have not seen mention when talking about Octane numbers is the additives used by manufactures. You will find more additives in 97 Octane than in 87 Octane used for cleaning the engine's fuel system and help cut down bad emissions, but here is the rub. I have found engines that are designed to run on 87 Octane but are feed a steady diet of 97 Octane will have more deposits on the spark plugs over time due to the additives.

Is true there is technically more energy in 87 Octane than 97 Octane as the 97 is designed to burn slower in the higher compression engine. Even in the low compression engine say 9:1 if you put on a Turbo or a Supercharger you must run the higher octane if you are running boost and if you have a turbo Or Supercharger who don't twist up the wick once and a while?

All I'm saying is if you run high Octane fuel for feed for the steed then keep an eye on the spark plugs for crud build up and I'm talking about long time use.

https://www.jackssmallengines.com/diy/wp-content/uploads/2015/03/read-spark-plug.jpg

I wondered about that. I know in the past, better detergent and additive content was a selling point for high octane fuels. But these days even base model pickups and CUVs run direct injected, turbocharged engines capable of using 87 octane fuel. I assumed the better additive packages had migrated down to the lower octane blends, but don't actually know. Have any manufactures standardized the additive packages across all grades?

[BIGLRY]

Have any manufactures standardized the additive packages across all grades?
I have a few friends who are retired chemist or are still working in the petroleum industry, I have asked that same question of them and I have always got a positive NO! The higher Octane fuels get more additive. Other than Chevron which runs close to the same additive package in all their fuels grades I don't know of any, but that not to say some manufactures I'm not familiar with do.
Here is some trivia for ya.
"Chemical additives first entered the industry in the first decade of the century. These additives served a number of uses. For example, they lessened the capacity of gasoline to vaporize out of the gas tank or to polymerize (i.e., produce gummy residues) in the engine. In the early 1920s, the most important application for these substances was to eliminate knocking. Tetraethylead (TEL) was the first major gasoline additive to be commercialized for this purpose."

A nice read on Gasoline and Additives.
https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/gasoline-and-additives