Regular or High Octane Gas ?

[Grenvilleter]

Just curious who runs regular gas and who runs high test and reasons why.

I can't see the alcohol in low test gas doing rubber parts any good in the fuel system but the real question is, does the octane affect gas mileage?

Has anyone done comparative tests to determine if your runner's mileage is different between regular and high octane?

I just got my first runner ('97 Limited) a couple months ago and I'm still playing with it getting familiar and thought I'd tap into the collective knowledge here.
Thanks for your replies.
Terry

 

[DC runner]

You are getting things confused, at least in most places in the US. If you are referring to ethanol, understand that most places sell the same percentage formulate. This is regardless of octane level.

You will notice that pumps will disclose whether they sell ethanol formulated gas and they usually disclose something like this: All gas has 10% or less ethanol added.

Octane is different from formulation. Octane only deals with pre-detonation.

Some stations go out of their way to sell on 100% gas, but again, this is something utterly different from octane level.
And finally, the biggest waste of money is high octane. Unless you drive a expensive sport/luxury car that was specifically designed for high octane, you are putting money down the drain.

 

[rebelbowtie]

Unless your engine is tuned for higher octane fuel or has a high compression ratio and needs resistance to pre ignition the only thing high octane does is lighten your wallet.

 

[Grenvilleter]

You are getting things confused, at least in most places in the US. If you are referring to ethanol, understand that most places sell the same percentage formulate. This is regardless of octane level.

You will notice that pumps will disclose whether they sell ethanol formulated gas and they usually disclose something like this: All gas has 10% or less ethanol added.

Thanks for your reply. Fortunately, I'm not confused as where I live (in Canada) all low test gas has ethanol added up to 10% and the high octane does not.

All 2 stroke engines here are recommended to run high octane to avoid the ethanol component from drying out the base seals but that is not my initial question.

I'm also cognizant of the need for high octane on high compression engines to avoid pre-detonation issues.

Not withstanding the fact that ethanol does not have the same amount of available energy as gasoline (gallon for gallon), I'm curious if anyone has ever done mileage tests to see if there was any difference in fuel economy.

I also understand that doing controlled tests between the two can be a challenge due to varying factors like headwind and tailwinds, hills or flat terrain or speed that we drive at.

Understandably, if high-test and low-test is essentially the same in the US (other than octane rating), doing the test would be futile.

 

[DC runner]

Aww. Well, ok. You answered your own question. Ethanol has less "power" than gas, so you would see a decrease in MPG. Whether you are able to determine that out of driving habit, which has far more impact, who knows.

Also, sorry, I should have suspected not from US with your use of "high test"... we don't normally use that phrasing.

The KEY is the math. Does the increase in the cost of higher octane, with the small increase in MPG, make it worth it? You have to do the math yourself. Most times, usually not, but if the high octane is cheaper than it usually is... then perhaps.

 

[jrm]

If it matters

i run mid grade 89 octane all the time.

 

[98OzarksRunner]

In theory, ethanol has 20-30% less energy than gas, but when mixed at 90/10 it doesn't make much difference. We used to have an 06 Mustang GT and back before Missouri started blending ethanol with gas (and Illinois did - has for years) I would lose 1 mpg (~5%) after filling up in Illinois. Since premium is usually $.20 (or more) per gallon than regular, you might break even when gas hit $4 per gallon (maybe).

Ethanol won't hurt your fuel lines or other rubber components. Cars have been designed for fuel with ethanol since the 1980s. Classic cars and muscle cars from the 60s have fuel lines dry out from ethanol, but a 50-year-old fuel line needs replaced anyway. I burn E85 (85% ethanol) in my 65 Mustang. It's the 'poor man's racing fuel', or as I like to think of it - the 'thinking man's racing fuel'. It's at least 105 octane, and summer blend is usually about 108 octane, great for high-compression or supercharged/turbocharged engines (provided you upgrade the fuel system and retune for ethanol).

 

[Grenvilleter]

Aww. Well, ok. You answered your own question. Ethanol has less "power" than gas, so you would see a decrease in MPG. Whether you are able to determine that out of driving habit, which has far more impact, who knows.

Also, sorry, I should have suspected not from US with your use of "high test"... we don't normally use that phrasing.

The KEY is the math. Does the increase in the cost of higher octane, with the small increase in MPG, make it worth it? You have to do the math yourself. Most times, usually not, but if the high octane is cheaper than it usually is... then perhaps.

Well...I'm bordering on "old fart" status and the use of Low/High test may be a throw back expression from days gone by.
No need to apologize.

I also should have not used the term "high octane" as it denotes the octane rating only and does not take into consideration the additives premium gas may or may not have present.

On previous other vehicles I have owned, using premium in some instances made a considerable difference in mileage and other vehicles no difference was seen (especially carburated engines).
On my injected engines, on a couple of occasions, I found the regular grade gas would tend to foul up the injectors after a time and after running premium for a couple of tankfuls , it seemed to help smooth out the running.
Perhaps there is some sort of injector cleaner in premium fuel?

Many here will say premium gas is a waste of cash on a lower compression engine but my experiences have been varied all the way from a complete waste of money to the opposite being better fuel economy and a cleaner, more efficient running engine.

Perhaps regular gas and a can of injector cleaner on occasion to help keep things clean but I'll try to do some tests as objectively as I can and find out what works better for me and my style of driving.

 

[Shibby!]

Thanks for your reply. Fortunately, I'm not confused as where I live (in Canada) all low test gas has ethanol added up to 10% and the high octane does not.

All 2 stroke engines here are recommended to run high octane to avoid the ethanol component from drying out the base seals but that is not my initial question.

I'm 98% sure this is incorrect. Yes, 2-smokes do not like, or should be run with ethanol, however gas stations don't generally have one grade with and one without ethanol. There may be a few exceptions (i think Shell Vpower is one of them), but most gas stations have ethanol in both regular/midgrade and premium.

I run regular in all low compression and normally timed engines. Best bet is run what the manufacture recommends. I do have experience running regular and premium in a few different motorcycles and some have gotten better mileage with premium. I can't explain that other then maybe the slower delayed combustion may help produce slightly more even power requiring less throttle. I always default back to what the manufacture recommends though.

 

[Grenvilleter]

I'm 98% sure this is incorrect. Yes, 2-smokes do not like, or should be run with ethanol, however gas stations don't generally have one grade with and one without ethanol. There may be a few exceptions (i think Shell Vpower is one of them), but most gas stations have ethanol in both regular/midgrade and premium.

I run regular in all low compression and normally timed engines. Best bet is run what the manufacture recommends. I do have experience running regular and premium in a few different motorcycles and some have gotten better mileage with premium. I can't explain that other then maybe the slower delayed combustion may help produce slightly more even power requiring less throttle. I always default back to what the manufacture recommends though.

Shibby... you could be right and I certainly take the gas jockey's info with a grain of salt.
Who knows all the secrets that gas companies use in their "formulations".

On a side note pertaining to gas companies, Anyone remember the Sunoco's purple "high-test" gas with the 94 octane rating ?

Back in the day when I was a bit of a "piston head" 30-40 years ago, some folks with the high compression engines would claim only the purple premium gas would adequately do the job but they would be running 11:1 comp ratio's. Of course this was purely an octane thing but today, who knows what additives are added to "enhance" your driving experience.

 

[DC runner]

All about timing.

Motorcycles are about a decade, or more, behind the tech curve. They are being pulled, kicking and screaming, into the modern world. The EPA finally had to yell at them about not moving toward better combustion cycles. I am an avid motocycle rider and owner and you have to BE very careful about the type of gas you use in some motorcycles. Cars have, for at least the last 20 years, had knock sensors and electronic timing/injection which makes the concept of high octane a waste in all but a few vehicles.

Motorcycles? While many of your high end, name brand bikes have moved toward electronic FI and the use of knock sensors to be able to use all octane levels... many of your base models have not.

When you run a straight mechanical carb, you don't have a knock sensor or electronic engine control that can adjust timing to run all grades. Hence, you can get some nasty, nasty pinging on that poor little bike engine.


Slowly, they are finally starting to adopt electronic timing and engine control and water cooled. This means they can burn hotter (and cleaner with better MPG) and utilize all grades of fuel.

Most of us forget this, since many don't even remember a time you had to ACTUALLY watch what kind of gas you could use. I used to carry octane boost in my older bike because on long trips you would occasionally come across a small gas station out of the higher octane I needed, and I would have to run 87... which made that particular bike ping.

Anyway. That is why on bikes, even today, it still matters. As a biker, I am a fan of the new innovations FINALLY hitting bikes.

 

[Shibby!]

Of course this was purely an octane thing but today, who knows what additives are added to "enhance" your driving experience.

I'm thinking it's similar to everything else. Marketing and margins.

All about timing.

Motorcycles are about a decade, or more, behind the tech curve. They are being pulled, kicking and screaming, into the modern world. The EPA finally had to yell at them about not moving toward better combustion cycles. I am an avid motocycle rider and owner and you have to BE very careful about the type of gas you use in some motorcycles. Cars have, for at least the last 20 years, had knock sensors and electronic timing/injection which makes the concept of high octane a waste in all but a few vehicles.

Motorcycles? While many of your high end, name brand bikes have moved toward electronic FI and the use of knock sensors to be able to use all octane levels... many of your base models have not.

When you run a straight mechanical carb, you don't have a knock sensor or electronic engine control that can adjust timing to run all grades. Hence, you can get some nasty, nasty pinging on that poor little bike engine.


Slowly, they are finally starting to adopt electronic timing and engine control and water cooled. This means they can burn hotter (and cleaner with better MPG) and utilize all grades of fuel.

Most of us forget this, since many don't even remember a time you had to ACTUALLY watch what kind of gas you could use. I used to carry octane boost in my older bike because on long trips you would occasionally come across a small gas station out of the higher octane I needed, and I would have to run 87... which made that particular bike ping.

Anyway. That is why on bikes, even today, it still matters. As a biker, I am a fan of the new innovations FINALLY hitting bikes.

Give me a carbed bike any day. I will fight FI tooth and nail till I'm forced to buy one.

It all depends on the bike. On a street bike, fine, on a cruiser, fine (although that takes all the fun out of it), but on a dual sport or adventure bike? Screw the FI. I want something I can fix and know will work.

People say electronics are reliable, but you tell that to people with FI bikes that break down 50 miles in the the back country and 100's away from help or a mechanic. Often 1000's away from a mechanic that can actually fix or diagnose a FI electrical system.

Give me a philips screwdriver and some other basic tools and I'll get a carbed bike running!

There are places for FI and there are times it's not wanted. IMO, adventure bikes should not have FI.

Back on topic... =)

 

[DC runner]

Meh. People complained when cars went to FI, but it made them better not worse and cars today are much more reliable. Carbs are cranky in the cold and different weather. Get mucked up way to easily.

The high end bikes that went EFI about a decade a go are much better in terms of reliability than a carb. The ole "give me simple" adage is kinda just humans hating change. I have a carb'ed bike and I own a newer EFI and my EFI starts every time. Every time. It gets better MPG and runs cleaner. That ins't a bad thing.

As for broken down on the side of the road. Your air cooled, carb'ed bike is much more likely to break down on the side of the road. Air cooled overheat when it is too hot and those small carb jets love to muck up. I have had to pull my jets, on the side of the road, that is not fun.

I get that water cooled means more moving parts... I get that. But water cooled engine design isn't exactly new. This is "old" technology that has been around reliably for about 50 years.

New mandates are pushing most large CC bikes toward water cooled for a myriad of reasons, many have already gone there and I haven't seen any marked increase in break downs. In fact, I bet that in a few years we are going to see a decrease.

I have no idea if those kinda stats are kept, but the combination of water cooled and efi made cars more reliable, I imagine the same will be done with bikes. Once you move to water cooled, you get MUCH more controlled heat patterns which means you can build a much, much tighter engine. You will know exactly where that engine will be in terms of temperature, which plays a huge part in how you design the engine.


Like today, I love tinkering with my buddies 70 International travel all. Carb, points and all... but, I would never want to use it as a daily driver. Even on the best of days, that thing is temperamental. Click and go, the beauty of knowing your car will just GO is an amazing gift given by electrical and water cooled systems.

 

[KHoffRunner]

The only CEL I've ever thrown was while I had premium gas (91) in the tank and my mph increase was so minimal it wasnt worth looking at the stupid light in the dash.

 

[giguchan]

I sometimes use the term High test AND sometimes even Ethyl... just to be a smart ass... thing is if you dont put in High test you wont get ur knife set or set of glasses..

Now where did i put my Greenstamps?

 

[JohnsD90]

I run the cheapest **** i can find, I get 19-21mpg almost every single tank, and i don't baby it either, cruise at 75-85+mph for over half my 35 mile each way commute.

Not gonna piss money on expensive gas when the car wasn't even designed to use it, or when it has no benefits from it.

 

[GetOut]

As has been said, use low octane gas for a low compression truck. What's worth spending extra money on is fuel with good additives. Gas is not great for engines. It can use a bit of helper to keep the system clean. That's why Chevron has has my business for years. Techron-87 octane.

 

[agloukhoff]

Wow there is a lot of confusion and misinformation in this thread. So let me try to clear it up..


What does high octane mean:
High octane rating means the fuel is more resistant to predetonation. This is extremely important in cars with advanced timing or designed to run on high octane fuels as low octane fuels will certainly cause predetonation.

What is predetonation:
Predetonation occurs when the fuel is injected into the cylinder on it's compression phase and the heat of the engine/cylinder cause it to detonate before the piston has come all the way up. This can bend of break rods which is why all FI cars have a knock sensor which re****s the timing when it senses predetonation. This doesn't mean you can run 87 in your 93 tuned car and expect the knock sensor to make it all ok. The ECU will re**** the timing temporarily so it will knock again and again and again.

How do I know if I need high octane:
Well - are you getting engine knock with 89 or 87? No? Then you don't need it. That's really all there is to it.

How do I know I have engine knock:
Best way, ODB2 readers, Dashhawk, ScanGuage do it. Or you can go oldschool and listen for it...

Doesn't premium gas have less ethanol?
No to all. In fact, what ethanol is exactly what is added in a larger quantity to high octane gas to make it "high octane". In short, 87 will have LESS ethanol than 93. So if your only reason for running 93 is "ethanol is evil" - you're running the wrong gas.

Is High Octane going to be better mpg?
In terms of MPG, high octane fuel being more resistant to predetonation actually has LESS usable energy than low octane fuel. So unless your engine is able to take advantage and run with advanced timing when using high octane gas, you will see actually have LESS power with high octane gas -but we're talking highly theoretical amounts and nothing short of a series of dyno tests will show it. Like..these: Fifth Gear - Fuel additives test - YouTube

But Shell tells me that their awesome additives in 93 make my engine extra clean and super powerful.

First all gas has detergens in it. It's an EPA requirement. What the additives are all super secret and you have no idea what they are and they are different for all gas stations in different quantities:
BP 87 Octane ... 17.2 milligrams per 100 milliliters
BP 93 Octane ... 26.4 milligrams per 100 milliliters
Citgo 87 Octane ... 6.0 milligrams per 100 milliliters
Citgo 93 Octane ... 9.4 milligrams per 100 milliliters
Exxon 87 Octane ... 20.0 milligrams per 100 milliliters
Exxon 93 Octane ... 21.2 milligrams per 100 milliliters
Pilot 87 Octane ... 5.8 milligrams per 100 milliliters
Pilot 92 Octane ... 8.8 milligrams per 100 milliliters
Shell 87 Octane ... 16.2 milligrams per 100 milliliters
Shell 93 Octane ... 31.0 milligrams per 100 milliliters

Is more better? I dunno. Nobody can tell you except the fuel company and they never will.

So if you really want to make sure your engine runs super clean, run 87 and then buy some Seafoam with all the money you save.


As far as the carb vs FI thing. FI is better in every way imaginable and is stupidly reliable. In 30k miles on 2 FI bikes, I have had all kinds of problems - one of them is British - but not a single one was FI related. If anything, FI and the ECU have made things better and easier.

My only carb experiences was in a race tuned camaro which was used for 24h endurance racing. It ran like an absolutle champ when the temperature was exactly where it needed to be, got to hot or too cold - enjoy the backfires. Never again.

 

[BamaDrewski]

I wanted to throw in my two cents worth here. I have a 2000 T4R Limited with 4WD and it just turned over the 200K mark. When non-ethanol based fuel became available her in the Southeastern US, I started using it exclusively. It is available here in 87, 89 and in rare cases 93 octane. From first hand experience, I have noticed better fuel economy and seemingly better performance. When I have had to use the ethanol base fuel (like while on a road trip where I can't find non-ethanol) I have seen a decrease in mileage. ALSO, I have read where ethanol actually attracts moisture and can create a "gel" substance in fuel supply lines, fuel regulators and other areas. For me, it's simple, I will pay a few cents more for the 100% gasoline product any day. Something about burning an agriculturally produced product in my truck that was designed for "real gas" is the only convincing I need. Not sure if this helps but IMHO, 100%/non-ethanol gas is the better choice if it is available.

 

[agloukhoff]

I wanted to throw in my two cents worth here. I have a 2000 T4R Limited with 4WD and it just turned over the 200K mark. When non-ethanol based fuel became available her in the Southeastern US, I started using it exclusively. It is available here in 87, 89 and in rare cases 93 octane. From first hand experience, I have noticed better fuel economy and seemingly better performance. When I have had to use the ethanol base fuel (like while on a road trip where I can't find non-ethanol) I have seen a decrease in mileage. ALSO, I have read where ethanol actually attracts moisture and can create a "gel" substance in fuel supply lines, fuel regulators and other areas. For me, it's simple, I will pay a few cents more for the 100% gasoline product any day. Something about burning an agriculturally produced product in my truck that was designed for "real gas" is the only convincing I need. Not sure if this helps but IMHO, 100%/non-ethanol gas is the better choice if it is available.

Non ethanol gas IS better and will give slightly better mpg. No argument there - but it's very difficult to find in some places.

The problem with ethanol and water isn't so much that ethanol "attracts moisture" it's that alcohol unlike oil will mix with water and will absorb it from the air. I've never heard of it "gelling" but I have seen it cause metal fuel tanks to rust as ethanol release the water that it has absorbed from the air over a period of time due to temperature changes etc. It's a really common issue for motorcycles stored over the winter with less than a full tank.