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Old 08-22-2016, 12:18 PM   #1
sum-r breeze
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Default Premium Gasoline ?

Does anyone know why all the name brand gas stations ( with the exception of the Sunoco near the Margate ) have only 91 Octane for super unleaded? The price is better than down here in Mass but the octane here is 93 for the super. Does the lower octane number have something to do with the 600 feet above sea level in the lakes region? The Sunoco station has a separate pump nozzle for their "Ultra 93" so it IS available but for more money....

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Old 08-22-2016, 11:37 PM   #2
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When I lived in Co at over 7000 ft, the premium was 91. Higher altitude=less oxygen=lower combustion ratio=less octane needed. But I don't think 600 ft would make a dif. Maybe today's cars with knock sensors and computer controlled timing advance don't need the higher octane.
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Old 08-23-2016, 10:10 AM   #3
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Default Premium Gas

The oil industry would like you to believe that higher octane gas makes your engine run better, this is mostly a false claim. Some engines actually do require higher octane gas due to combustion ratio only. IF your car has a combustion ratio of 9.5:1 or lower then you do not need anything above 87 octane. My old Honda civic would even run on 86 octane if you could find it. My BMW has a combustion ratio of 10.1:1 and requires 89 octane. The only cars or engines that require 91 or 93 octane have high compression ratios or turbochargers.

For boats we are spoiled due to most of the marine gas being 92 octane and it also contains no ethanol (a whole other topic for another thread). The marine gas is only a 20% premium over pump and is worth every penny.

The 600-feet altitude it will have almost no effect on gasoline combustion. The air temperature will have much more of an effect at this altitude. You need to be at 3000-ft altitude or greater before the air pressure has an effect on combustion.
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Old 08-23-2016, 10:29 AM   #4
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Originally Posted by CaptT820 View Post
For boats we are spoiled due to most of the marine gas being 92 octane and it also contains no ethanol (a whole other topic for another thread). The marine gas is only a 20% premium over pump and is worth every penny.

Which marina has this 92 octane ethanol free gas available on the lake?

As far as I am aware, most of the gas available at marinas on the lake is 89 octane gasoline that does have up to 10% ethanol.
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Old 08-23-2016, 11:04 AM   #5
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Which marina has this 92 octane ethanol free gas available on the lake?

As far as I am aware, most of the gas available at marinas on the lake is 89 octane gasoline that does have up to 10% ethanol.
Y Landing used to be the only place on the lake that had 91 octane. I heard (hearsay) they no longer carry it and only have 89 octane like everyone else...

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Old 08-23-2016, 11:14 AM   #6
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I believe Rich is correct. I am not aware of any marinas selling ethanol free gas. Unless you live in Alaska or Hawaii it's getting tough to find it. I have been told aviation fuel is ethanol free if you have access to an airport that services small planes.

http://www.pure-gas.org/index.jsp?stateprov=NH
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Old 08-23-2016, 02:04 PM   #7
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The Mobil in Meredith has 93 octane. Great little gas station/convenience store. But not sure why most sell the 91.
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Old 08-23-2016, 02:16 PM   #8
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Originally Posted by CaptT820 View Post

For boats we are spoiled due to most of the marine gas being 92 octane and it also contains no ethanol (a whole other topic for another thread). The marine gas is only a 20% premium over pump and is worth every penny.
As others have stated this is false.... Marina's on the lake sell you 89 octane.... and most Marine engines specify its use.... Also there is no pump on the lake that is ethanol free... Most of them have pre-treated gas with additives to reduce the risk of ethanol, but that is the extent of it.
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Old 08-23-2016, 03:48 PM   #9
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Originally Posted by sum-r breeze View Post
Does anyone know why all the name brand gas stations ( with the exception of the Sunoco near the Margate ) have only 91 Octane for super unleaded? The price is better than down here in Mass but the octane here is 93 for the super. Does the lower octane number have something to do with the 600 feet above sea level in the lakes region? The Sunoco station has a separate pump nozzle for their "Ultra 93" so it IS available but for more money....

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I asked the same question some years ago to the driver of a gas tanker dropping a load of gas at Murphy's Mobil (now Irving) at the corner of Moultonboro Neck Road.

He was dropping a load of 93 octane gas that came up from the Chelsea/Revere fuel terminal in MA. He said most fuel delivered to NH stations originate from the Portsmouth fuel terminal that carry only 91 octane for their premium.

Some gas stations in MA like Shell and Sunoco list 93 Octane for their premium. Many others show 91 octane.

Long gone are the days of 104+ for Sunoco 260. And yes, it made a difference for the 11 to 1 or higher compression fire breathers roaming the streets.
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Old 08-23-2016, 08:10 PM   #10
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Default Ethanol free

Moultonboro airport has ethanol free gas. It does carry quite a premium.
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Old 08-23-2016, 08:25 PM   #11
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Moultonboro airport has ethanol free gas. It does carry quite a premium.
I have heard that as well. It is my understanding that it is 100 octane and has lead in it.
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Old 08-23-2016, 09:28 PM   #12
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Default Premium Fuel

I purchased AV gas at Laconia Airport for my boat today, 100 octane, no lead, no ethanol. Ethanol is not good for my engine and you know the problems with hoses and internal engine parts especially on antique engines. Maybe as a side effect I notice that there is extremely little exhaust odor if at all.
Appears most marinas have low octane regular gas. I did purchase some gas at Channel Marine but will not do again due to the docking difficulties. Spoke to a local gentleman today who told me he had the same problem I had at Channel when he had a boat.

I am a retired workaholic and continuing aquaholic.
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Old 08-24-2016, 05:13 AM   #13
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I think the fuel sold at local airports is AV 100LL for low lead. I know the Government is moving to remove the lead from aviation fuel, but has not found an acceptable alternative for the older piston engines.

This information is about a year old, and perhaps they have removed the lead, but I have not read anything about it.
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Old 08-24-2016, 09:11 AM   #14
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Default Ethanol

I apologize for placing information that is inaccurate. I must have been thinking of another fuel when I placed my post.

It is correct that the marine fuel sold on the lake contains ethanol (most likely 10%) and is most likely 89 octane. The fuel does however contain additives and stabilizers that allows it to fend off phase separation for up to at least a year (in the case of ValvTect Fuel). I would love to see the marine stations get rid of the ethanol instead of treating the ethanol, but one thing at a time.

For those who would like to track down truly non-ethanol fuel you can go to the following site which lists each location where it can be found in each state:
www.pure-gas.org/
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Old 08-24-2016, 11:52 AM   #15
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Long gone are the days of 104+ for Sunoco 260. And yes, it made a difference for the 11 to 1 or higher compression fire breathers roaming the streets.
The bore and head design have a lot more to do with octane need than CR, IMO. The typical small airplane engine that needs 100 octane will have a CR of <9:1, but the bore is typically HUGE at 5" or more and the spark plugs are way off center (though there are two so, maybe not a big deal unless one magneto fails). I have a daily driver (rider) with 12.2:1 CR that runs just fine on 91 octane. It has a small bore (75mm) and a centrally locate spark plug, so it does not much spark advance.
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Old 08-24-2016, 01:21 PM   #16
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Tedeschi (Formerly Fullers) in Moultonborough has 93. Filled up the fun car on vacation and noticed the premium had the 93 sticker not 91.

It's becoming more common to find cars that "can" run on 87 but that will benefit from higher octane, just one of the advantages of advanced engine management controls. In the case of the fun car, it's a roughly 15 HP / 20 ft. lb. torque difference between regular and premium according to the owner's manual. I'm sure this mostly due to the EMM being able to advance the spark timing more with the higher octane fuel. When in doubt, check the owner's manual, if they recommend 87 there's no point in putting anything else in.
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Old 08-24-2016, 02:02 PM   #17
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I'm sure this mostly due to the EMM being able to advance the spark timing more with the higher octane fuel. When in doubt, check the owner's manual, if they recommend 87 there's no point in putting anything else in.
Yup, unless it's boosted, altering the ignition timing is all you can do to get more power with higher octane.
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Old 08-24-2016, 06:00 PM   #18
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Octane is a measurement of how explosive the gasoline is. The higher the octane rating, the less explosive the gas is. Higher octane prevents preignition. As the Gas/Air mixture is compressed in the cylinder it heats up. The higher the compression the hotter it gets. If it gets too hot it will ignite before the spark plug fires, and cause engine knock, which will damage engine bearings and burn holes in piston heads.

Octane is not a measurement of the energy contained in the gas, so a higher octane does not provide more power or better gas mileage. If your car or boat engine sounds like it's full of marbles, especially if you are in 4th gear going up a hill or accelerating hard, your engine is knocking and moving up to a higher octane will probably help. If it doesn't, have your engine timing checked.

Other than that, you should use the octane level your car or boat engine specifies. Using a higher octane will not provide you with any benefits, but it will make the oil companies richer!

Haven't seen it in NH, but in Florida many of the gas stations advertise no ethanol gasoline for boats.
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Old 08-25-2016, 07:22 AM   #19
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Default Modern engines

The more advanced engines today not only burn cleaner but provide better mileage. MBs, BMWs and Audis requires 91 in the states, more in Europe. The ECM compensate for lack of high octane in the states. I was told by other European performance car owners that they notice a difference if they find higher octane gas.

The new 4 cylinder, turbo engines provide as much HP and torque as the old small block V8. They do require higher octane to prevent knocking, especially when the turbo kicks in.

I read somewhere that there will be a demand for 91+ octane in the future because of the strict emission as well as gas consumption regulations. This will cause the refineries to produce higher octane gas and hopefully the price will go down. Today the refineries are not producing enough high octane gas so the prices are high.
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Old 08-25-2016, 07:39 AM   #20
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Octane is a measurement of how explosive the gasoline is. The higher the octane rating, the less explosive the gas is. Higher octane prevents preignition. As the Gas/Air mixture is compressed in the cylinder it heats up. The higher the compression the hotter it gets. If it gets too hot it will ignite before the spark plug fires, and cause engine knock, which will damage engine bearings and burn holes in piston heads.

Octane is not a measurement of the energy contained in the gas, so a higher octane does not provide more power or better gas mileage. If your car or boat engine sounds like it's full of marbles, especially if you are in 4th gear going up a hill or accelerating hard, your engine is knocking and moving up to a higher octane will probably help. If it doesn't, have your engine timing checked.

Other than that, you should use the octane level your car or boat engine specifies. Using a higher octane will not provide you with any benefits, but it will make the oil companies richer!


Haven't seen it in NH, but in Florida many of the gas stations advertise no ethanol gasoline for boats.


If the owner's manual of your modern (anything with a knock sensor) car says to use premium, the engine will likely run at reduced power with low octane fuel. I agree with you, it's not because the low octane fuel contains less energy, it's because spark timing needs to be retarded to keep the combustion chamber temperature lower to prevent pre-ignition. There is nothing you can do to adjust timing manually on these engines, the ECU will take care of that automatically.

If an engine was designed to make use of high octane fuel, the ignition timing will be set such that peak combustion chamber pressure occurs at the same time that the connecting rod can apply the most leverage (for the longest time) to the crankshaft. If you retard the timing to reduce the heat generated, you reduce the time that the combustion gases push down on the piston and that reduces power.

The 5.9 liter V8 in my old 99 Dodge had modern electronics, but no knock sensor. The timing was set such that it ran fine (occasional light spark knock) on 87 octane with no load, but if I was towing, it would knock and ping like crazy. For towing season, I always filled it with premium and I swapped out the 192 degree thermostat for a 180 degree. Despite having a normal distributor, you cannot alter the timing on these 5.9 engines. The computer will just adjust the timing to whatever it's programmed to regardless of the distributor position.

You can get ethanol-free boat gas in VT and NY. In my experience, it's more common than E10 at marinas there.
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Old 08-26-2016, 08:11 AM   #21
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If you want 93 gas, I just saw some yesterday at the Shell station at exit 20 in Tilton.
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Old 08-26-2016, 01:22 PM   #22
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Goodhue& Hawkins has 93 octane with Star-tron additive to deal with the ethanol. It's only $2.99 per gallon this year.
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Old 08-26-2016, 06:45 PM   #23
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Cobalt I believe you are correct in that AV 100LL is low lead.
Sorry for the misinformation I put here.
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Old 08-27-2016, 11:38 AM   #24
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The lead in the fuel is better for older engines providing valve lubrication. I use AV fuel in an older car for this reason, and the increased octane.

Who knew we would buy fuel from an airport for our older boats and cars?
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Old 08-27-2016, 05:27 PM   #25
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I don't generally pay attention to the octane levels in fuel, but today I gassed up at an Irving Main Way and their premium was 93. Since the OP was not on the lake (or posting about octane available ON the lake) I find this relevant.
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