Using 89 octane for first time.

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MANual_puller

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I think you missed something. And got righteous about something irrelevant to my last post.

Lowering/raising the evap point of the gas is for combustion efficiency. Fuel needs to vaporize during the process of combustion. Octane isn't the key point with that. Octane is a definition for how much pressure the vaporized fuel can sustain before spontaneously combustion.

Different fuel blends for summer and winter are for this reason:
When the air charge is cold (like in the winter months), the gas (regardless of octane) needs to have a lower evap point, so it can atomize, and then vaporize, yielding efficient combustion, otherwise engines would drivability problems like hard starting, lean mixtures, ect. When the air charge is hotter (summer) the evap point needs to be higher, so it doesn't cause the opposite drivability problems, like vapor lock, general rich conditions, poor emissions ect..

Gasoline volatility is regulated by the EPA, so you can read all about it on their website.

Nope, not getting righteous or saying you were wrong or trying to dispute any points. I was just adding to what you said. :) The "you" in my post was generic for the world and not directed at anyone in particular. :)


Thank you :)

My entire point is that winter blend fuel does not affect fuel mileage. It's the denser cooler air that is the culprit :favorites13: Port injection atomizes well enough that once the engine is running fuel mileage is unaffected. It helps with easier starts in the winter when the fuel is cold and that's about it.
 

Kotta390

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Lol I have always gotten slightly better fuel economy in the winter.
 

GP4L

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Nope, not getting righteous or saying you were wrong or trying to dispute any points. I was just adding to what you said. :) The "you" in my post was generic for the world and not directed at anyone in particular. :)



Thank you :)

My entire point is that winter blend fuel does not affect fuel mileage. It's the denser cooler air that is the culprit :favorites13: Port injection atomizes well enough that once the engine is running fuel mileage is unaffected. It helps with easier starts in the winter when the fuel is cold and that's about it.


Gotcha.

You are absolutely right about the denser air charge requiring more fuel. But winter blends do contain more butane than their summer blend counterparts. Butane raises the volatility of the gasoline, yielding less energy / less mpg. All this information is readily available, and accurate, from many sources.

But regardless, I mostly agree with your point. IMO it's not that big of a factor in the typical MPG reduction in winter months. I've had plenty of good MPG tanks throughout the winter, and plenty of bad MPG tanks in the summer, lol. The myriad of other non-fuel related variables play a much bigger role in economy. Most of those variables come from the nut that is between the seat and steering wheel. :roflsquared:
 

MANual_puller

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Gotcha.

You are absolutely right about the denser air charge requiring more fuel. But winter blends do contain more butane than their summer blend counterparts. Butane raises the volatility of the gasoline, yielding less energy / less mpg. All this information is readily available, and accurate, from many sources.

But regardless, I mostly agree with your point. IMO it's not that big of a factor in the typical MPG reduction in winter months. I've had plenty of good MPG tanks throughout the winter, and plenty of bad MPG tanks in the summer, lol. The myriad of other non-fuel related variables play a much bigger role in economy. Most of those variables come from the nut that is between the seat and steering wheel. :roflsquared:

Yup. I swear, I would get a ton better mileage if this truck weren't so fun! :happy107: Volatility makes no difference either as long as the evap system is working properly. Once it's in and the cap on there's no where for it to go. 89 octane winter fuel has the same energy as 89 octane summer fuel(well it's supposed to but I guess there's probably a tolerance range, it should be a negligible difference if there is one) By law stations can't falsely advertise :favorites13:
 

GP4L

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Yup. I swear, I would get a ton better mileage if this truck weren't so fun! :happy107: Volatility makes no difference either as long as the evap system is working properly. Once it's in and the cap on there's no where for it to go. 89 octane winter fuel has the same energy as 89 octane summer fuel(well it's supposed to but I guess there's probably a tolerance range, it should be a negligible difference if there is one) By law stations can't falsely advertise :favorites13:

Well, you are disagreeing with the U.S. Department of Energy regarding the possible lower energy content in winter gasoline. The Evap system has nothing to do with that (however, your general statement about the evap system is correct - if it's functioning properly).

Butane has fewer carbon molecules in it than gasoline mixtures - the higher % butane in the gasoline (which goes up for winter blends), the less energy that fuel has. Just like adding ethanol to gasoline.

But it depends on the gasoline mixture. Some gasoline mixtures are so bad to begin with, they have the same number of carbon molecules as butane, which means adding more butane won't lower the energy content. However, most gasoline has 30-60% more carbon molecules than butane, so adding butane to raise the volatility ("solving" the vaporizing "issues" in the winter), lowers the energy content some. Again though, it all depends on how much % butane is added/increased over the summer blend. They (US DoE) say 2-8% reduction in fuel economy because of the FUEL. The rest of the reduction in economy come's from the uncontrollable variables (weather), and the vehicle operator.

However, I don't think you are wrong in saying that it's likely negligible based off of fuel. 2% would be; instead of achieving 21mpg on the highway, one achieves 20.58mpg instead. That difference could probably be compensated for by reducing cruising speed a little bit. If anybody actually cares about <0.5mpg loss...
 

MANual_puller

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I wish they would just do away with the winter fuel all together. Then it would be a non-issue for sure :happy107: Modern port fuel injection(some new gas engines even use direct cylinder injection) atomizes well enough that starting shouldn't be an issue. TBI and carburated vehicles are the only ones that benefit from winter fuel. It's not too difficult to formulate an additive so that old tech vehicles wouldn't have starting issues on good gas. Just another great example of the government not keeping up with tech....:happy107:
 

noupf

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update......

Same run as last night, best result using either 87 or 89 octane ( i am 1/4 way though a tank back on 89 ). Averaged 20.1 mpg. Kept my speed locked at 70mph on the highway and drove as i normally do for the couple miles when off the highway. I did notice that most of the stop lights went my way tonight, so that may have been good for a tenth or two.

this is my second run on the 89 octane as one of the previous posters mentioned that summer driving/blend can yeild better mpgs.

So far the 89 octane is looking to do about .5-.8 mpgs better than it did when i was using it in late winter and early spring as i started tracking the mpgs.

Still, the 87 and 89 are close to identical.

Truck does seem to have a little better responsiveness though when on 89.
 

Tim7139

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I'm not 100% convinced there's any difference in gasoline between summer and winter.

WinterGas from Petro Canada is available from November through March in all gasoline grades at Petro-Canada gas stations across Canada (except the Greater Vancouver Regional District, Vancouver Island and the Sunshine Coast). Other companies choose different swap dates.
 
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MANual_puller

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Good Lord. Yes there is a physical difference/chemical difference. I'm not 100% convinced there is any difference in mileage when using either summer or winter blend fuel that can be blamed on the fuel. They have the same octane ratings which means they have the same energy/volume. The noticeable difference comes from PCM tuning keeping a constant a/f ratio with air that's less dense(warmer) and also from less aerodynamic drag on the vehicle because it has less dense air(warmer) to push through. Does that clear up any confusion on what I meant? I apologize if it was confusing......
 

tjfdesmo

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I am not aware that there is a correlation between octane and BTU content. Octane is a measure of resistance to pre-ignition not energy content AFAIK.
 

MANual_puller

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this answers the octane/power/clean fuel issue..Now this is discussed with a car as you will see in the vid WITHOUT MODS of any type..

https://www.youtube.com/watch?v=FPPkPAbzwbU

Per the findings in this video(same thing I said all along): unburnt fuel going out the tailpipe coupled with same mileage does mean there's more energy in higher octane fuel although "normal cars" don't seem to utilize it(that is well known as well).

With tuning to take advantage of the fuel there's a fair amount to gain. Hemi tuning is pretty aggressive from factory. Even with 89 octane I was seeing a fair amount of knock retard. This tells me the engine didn't like the fuel. I switched to 91 octane and the knock retard has gone away. The engine was not knocking but the computer was having to compensate for the fuel to keep it from knocking.
 

Kotta390

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Per the findings in this video(same thing I said all along): unburnt fuel going out the tailpipe coupled with same mileage does mean there's more energy in higher octane fuel although "normal cars" don't seem to utilize it(that is well known as well).

With tuning to take advantage of the fuel there's a fair amount to gain. Hemi tuning is pretty aggressive from factory. Even with 89 octane I was seeing a fair amount of knock retard. This tells me the engine didn't like the fuel. I switched to 91 octane and the knock retard has gone away. The engine was not knocking but the computer was having to compensate for the fuel to keep it from knocking.

There is a huge amount of false knock that these computers detect. For one I switched from 87-89-93 and did many WOT pulls and the knock was the same. I don't agree that the Hemi tuning is aggressive from the factory at all. I believe there is an abundance of false knock.
 

tones2SS

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Use 87 when the 89 is recommended? Just to "save a few bucks"?!?! LMMFAO :fc5716bd:
Nahhhhhh, never. :Big Laugh:
 

MANual_puller

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There is a huge amount of false knock that these computers detect. For one I switched from 87-89-93 and did many WOT pulls and the knock was the same. I don't agree that the Hemi tuning is aggressive from the factory at all. I believe there is an abundance of false knock.

This is true, broken header bolts are a common hemi problem, that vibration can absolutely cause a false knock reading. Loose exhaust clamps, worn engine mounts, a chip out of the plastic cooling fan, tires out of balance....anything that causes a vibration can cause false knock readings.

It's not false knock when it goes away with higher octane fuel as was the case with my truck on DSP's towing tune. False knock would be there no matter what fuel just as you described :) That false knock is however making the PCM pull timing and taking down your performance......
 

craigsez

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I notice on mine(2016 sport with about 4000 mi)at lower rpm when your gettin on it a bit mine has a bit of ping/knock and i have no tuner or nothin..I always forget till AFTER i fill my tank to go up or down to see if there is a difference..
 

KCaudill

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I used 100% gas no ethanol. 87 Octane took a long trip to nashville, TN almost one tank of gas all freeway. Found out that it has more power, no ping or knock and gain about 3 more mpg. Went from 20mpg to 22.8mpg per the dash gage. 3rd trip since i bought the Ram, 2016 Ram 1500 sport 5.7 current miles on truck is 6500 miles
 
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