Regular Unleaded or Premium Unleaded?

[Topoguide]

Here's my $.02 between Premium and Plus

When living at 5000 ft in Utah I noticed a difference in performance. At 1000 ft in Phoenix I don't really notice.

I tracked my fuel mileage between premium and plus; the fuel mileage difference was worth the extra cost and actually saved me money. As my Cruiser has aged and fuel mileage has overall gotten worse (if anybody knows of a normal issue besides the MAF please let me know) the gap has decreased and the savings are not that noticeable.

NOTE: A few years ago I found that Costco Premium was about the same as Plus at other Top Tier vendors. I haven't checked recently.

 

[Pskhaat]

To resurrect yet again an old thread...

If you lived is Colorado and drove up mountains I would use Premium.

Other than this problem: Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen?

It makes no scientific sense, but a number of us notice more stall/vapor conditions on high-test at altitude.

 

[gatormark91]

To resurrect yet again an old thread...



Other than this problem: Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen?

It makes no scientific sense, but a number of us notice more stall/vapor conditions on high-test at altitude.

Ethanol boosts octane, and has a lower boiling point than gasoline.

 

[Pskhaat]

Ethanol boosts octane, and has a lower boiling point than gasoline.

Yup, but each octane blend rating has similar ethanol quantities per State regulatory regimes.

 

[Lonegrasshopper]

If you believe you're gaining between 5% - 10% in mpg by using premium over regular then you're still losing. How? Well, in my area 87 is $1.99/gallon, and 92 is $2.45. That's a 23% increase in cost. So, by this logic you would be spending 23% more to save 7.5%. I'm no math wizard, but...you lose.

Our engine is not a high compression engine that requires the higher octane. All the higher octane does is that it allows for greater piston compression before allowing the fuel to ignite. It prevents pre ignition combustion. That's it. Also keep in mind that the 87 is the minimum octane rating at that pump.

Here are some links about octane ratings, and no, we do not gain actual benefits from running premium.

Consumer Advice

The official website of the Federal Trade Commission, protecting America’s consumers for over 100 years.

www.consumer.ftc.gov

Select the right octane fuel for your vehicle!

We answer your most frequently asked questions about octane.

fueleconomy.gov

 

[abuck99]

I have a fairly heavy build (6500lbs running weight) compared to a stock truck so I'm constantly toting a load. I've been using Top Tier Premium primarily for the additional detergency and additives it contains. I may be misguided but my thought is that it burns slower, cleaner and reduces deposit build up in intake and top end. Makes for a cooler running, cleaner burning engine. I'm going to experiment with lower octane up at higher altitude (9k-12k feet) in the next couple of weeks and see how does and if it helps reduce excess vapor pressure in the tank.

@Pskhaat I read the entire thread this morning- noticed you've been here a while; contributing to the thread back in 2005! Long timer- .

Some takeaways on octane differences:

404 Error - Items of Interest - Sunoco Race Fuels

www.sunocoracefuels.com

404 Error - Items of Interest - Sunoco Race Fuels

www.sunocoracefuels.com

 

[SWUtah]

If you believe you're gaining between 5% - 10% in mpg by using premium over regular then you're still losing. How? Well, in my area 87 is $1.99/gallon, and 92 is $2.45. That's a 23% increase in cost. So, by this logic you would be spending 23% more to save 7.5%. I'm no math wizard, but...you lose.

Our engine is not a high compression engine that requires the higher octane. All the higher octane does is that it allows for greater piston compression before allowing the fuel to ignite. It prevents pre ignition combustion. That's it. Also keep in mind that the 87 is the minimum octane rating at that pump.

Here are some links about octane ratings, and no, we do not gain actual benefits from running premium.

Consumer Advice

The official website of the Federal Trade Commission, protecting America’s consumers for over 100 years.

www.consumer.ftc.gov

Select the right octane fuel for your vehicle!

We answer your most frequently asked questions about octane.

fueleconomy.gov

good article it states that you should use the octane rating required by your manufacturer 2015 LX 570 required octane rating per owners manual and gas cap premium fuel required. My 100 series LX premium fuel recommended not required. Come back when you have a source like Lexus that states they were just kidding about the required premium fuel. It’s your truck use gasoline you would like to use.

 

[J1000]

Ethanol boosts octane, and has a lower boiling point than gasoline.

Actually, ethanol has a higher boiling point than gasoline, a higher flash point, and raises the boiling point of the fuel when mixed with gas.

 

[ROAM]

I have a fairly heavy build (6500lbs running weight) compared to a stock truck so I'm constantly toting a load. I've been using Top Tier Premium primarily for the additional detergency and additives it contains. I may be misguided but my thought is that it burns slower, cleaner and reduces deposit build up in intake and top end. Makes for a cooler running, cleaner burning engine. I'm going to experiment with lower octane up at higher altitude (9k-12k feet) in the next couple of weeks and see how does and if it helps reduce excess vapor pressure in the tank.

@Pskhaat I read the entire thread this morning- noticed you've been here a while; contributing to the thread back in 2005! Long timer- .

Some takeaways on octane differences:

404 Error - Items of Interest - Sunoco Race Fuels

www.sunocoracefuels.com

404 Error - Items of Interest - Sunoco Race Fuels

www.sunocoracefuels.com

So turbo cars would never be able to run on anything less than 93 because their compression is too high? Meh.
Octane correlates to timing, advance/retard...to prevent knock...that's it. A lot of V8 NA cars run lower compression. The ECU will adjust to the fuel. The fact that these 4.7's live under 3k rpms and weigh 65 million lbs will limit the butt dyno calibration sensors. Meaning you'll never feel the difference but there is one.

 

[dnp]

So turbo cars would never be able to run on anything less than 93 because their compression is too high? Meh.
Octane correlates to timing, advance/retard...to prevent knock...that's it. A lot of V8 NA cars run lower compression. The ECU will adjust to the fuel. The fact that these 4.7's live under 3k rpms and weigh 65 million lbs will limit the butt dyno calibration sensors. Meaning you'll never feel the difference but there is one.

Actually, I have to say the 2UZ is the only engine I've ever had in a vehicle in which I can feel a perceptible difference in acceleration and overall performance when using 93 octane premium. I assume the knock sensors Denso provided must be hyper-sensitive, because overall driveability is noticeably better in my 2UZs that allow regular unleaded (2000 Land Cruiser requires premium, but my 2004 GX and 2005 Sequoia do not). Again, I've not been able to tell a difference in any other vehicle I've owned, but in anything 2UZ powered, there's absolutely a difference.

 

[Lonegrasshopper]

Actually, I have to say the 2UZ is the only engine I've ever had in a vehicle in which I can feel a perceptible difference in acceleration and overall performance when using 93 octane premium. I assume the knock sensors Denso provided must be hyper-sensitive, because overall driveability is noticeably better in my 2UZs that allow regular unleaded (2000 Land Cruiser requires premium, but my 2004 GX and 2005 Sequoia do not). Again, I've not been able to tell a difference in any other vehicle I've owned, but in anything 2UZ powered, there's absolutely a difference.

I'd be curious on what that difference is. Is it 20%+? Now a 23% increase in MPG on the low end would be 2 mpg, and the high 4 mpg. These are best case scenarios. Assuming on the low end with 87 you're getting 10mpg city, and 17 hwy. Very generous MPG. Now if premium, costing 23% more than regular, would increase performance by the same 23% then I would see a benefit, but otherwise I do not see an "ROI". I do not see the gained utility.

Let's average the difference to make it a 3 mpg increase. At 3 mpg additional average then, let's say we use 20 gallons of fuel, then we would gain an additional 60 miles out of that 20 gallons. With the new average mpg of 16.5 (average of 10 mpg and 17, and adding the 3 additional mpg), we in theory saved a hair over 3.63 gallons of fuel. 20 gallons of fuel at $2.45 = $49, and 20 @ $1.99 = $39.80. We spent $9.20 to go an additional 60 miles. Keep in mind we still were going those extra 60 miles, but we would have filled up sooner; however, those additional 60 miles would have cost us $8.84 using 87.

Sure we are discussing pennies here, but I seriously doubt it's an increase in performance over 20%. I don't care about feels. I can't trade on feels. Well, I guess I could, but they would be bad trades. Real world, do the math, pencil it out, and let us know when the costs equal the benefits. I guess I could make a spreadsheet running multiple scenarios, but I'm not because I do not see the numbers adding up.

 

[gatormark91]

Actually, ethanol has a higher boiling point than gasoline, a higher flash point, and raises the boiling point of the fuel when mixed with gas.

Ethanol boils at 173 degrees.
Some of the lighter distillates in gas (ie, pentane, butane octane additives) do boil at a lower point than ethanol. But since gas is mostly heavier molecules, gasoline's real-world boiling point is around 185-200 degrees.

Ethanol raises a gas formulation's RVP by about 1psi. So it is more volatile, which means it boils at a lower temperature. This is also affected by the lower atmospheric pressure at higher altitudes.

So, simply, if you run a truck with sea-level formula E10 up a mountain, it will get fuel boiling and vapor lock at lower elevations and lower temps than the same truck running non-ethanol gas.

Science!

 

[J1000]

Ethanol boils at 173 degrees.
Some of the lighter distillates in gas (ie, pentane, butane octane additives) do boil at a lower point than ethanol. But since gas is mostly heavier molecules, gasoline's real-world boiling point is around 185-200 degrees.

Ethanol raises a gas formulation's RVP by about 1psi. So it is more volatile, which means it boils at a lower temperature. This is also affected by the lower atmospheric pressure at higher altitudes.

So, simply, if you run a truck with sea-level formula E10 up a mountain, it will get fuel boiling and vapor lock at lower elevations and lower temps than the same truck running non-ethanol gas.

Science!

Pump gas starts boiling way lower than that. Ethanol raises the boiling point. Science...

 

[ramangain]

Science

 

[bamabrock]

they all taste the same

 

[abuck99]

“Its Poetry in motion, Science!”

Lets see who figures this one out

 

[prwillard2]

“Its Poetry in motion, Science!”

Lets see who figures this one out

You killed someone with science?

 

[gatormark91]

Pump gas starts boiling way lower than that. Ethanol raises the boiling point. Science...

Increase RVP and you decrease the boiling point.

10% Ethanol increases RVP by one point.

Therefore gas with 10% ethanol will have a lower boiling point than straight non ethanol gas, since it has a higher RVP.

The RVP of gas is measured and controlled by law in every state. The only time that is not controlled generally is in a state of emergency when people just need gas, like after a hurricane.

"Pump gas starts boiling way lower than that" isn't science without anything to back it up. It's just your opinion. And it's still not right.

404 Page Not Found

The American Petroleum Institute (API) is the only national trade association that represents all aspects of America’s oil and natural gas industry. Our more than 600 corporate members, from the largest major oil company to the smallest of independents, come from all segments of the industry.

www.api.org

"Vapor Pressure
Vapor pressure typically rises with the addition of ethanol to gasoline. The
increase is greatest at 10% by volume. At higher concentrations, the
vapor pressure of the blend decreases.
The magnitude of the vapor pressure increase associated with ethanol
addition becomes greater as the base fuel vapor pressure decreases. For
all ethanol levels, it rises steeply for blends produced using base gasoline
fuels with vapor pressures below about 9.5-10.5 psi. Above this level, the
vapor pressure of the base gasoline has minimal impact on the magnitude
of vapor pressure increase from ethanol addition.
Distillation
All levels of ethanol addition tend to lower the boiling temperatures in the
mid-range and back-end of the distillation curve.

At a given mid-range temperature (e.g., 200o
F), the percent of fuel
evaporated generally increases in proportion to the amount of ethanol
added to the base fuel."

Feel free to post up any scientific article that backs up your statement.

 

[gatormark91]

Increase RVP and you decrease the boiling point.

10% Ethanol increases RVP by one point.

Therefore gas with 10% ethanol will have a lower boiling point than straight non ethanol gas, since it has a higher RVP.

The RVP of gas is measured and controlled by law in every state. The only time that is not controlled generally is in a state of emergency when people just need gas, like after a hurricane.

"Pump gas starts boiling way lower than that" isn't science without anything to back it up. It's just your opinion. And it's still not right.

404 Page Not Found

The American Petroleum Institute (API) is the only national trade association that represents all aspects of America’s oil and natural gas industry. Our more than 600 corporate members, from the largest major oil company to the smallest of independents, come from all segments of the industry.

www.api.org

"Vapor Pressure
Vapor pressure typically rises with the addition of ethanol to gasoline. The
increase is greatest at 10% by volume. At higher concentrations, the
vapor pressure of the blend decreases.
The magnitude of the vapor pressure increase associated with ethanol
addition becomes greater as the base fuel vapor pressure decreases. For
all ethanol levels, it rises steeply for blends produced using base gasoline
fuels with vapor pressures below about 9.5-10.5 psi. Above this level, the
vapor pressure of the base gasoline has minimal impact on the magnitude
of vapor pressure increase from ethanol addition.
Distillation
All levels of ethanol addition tend to lower the boiling temperatures in the
mid-range and back-end of the distillation curve.

At a given mid-range temperature (e.g., 200o
F), the percent of fuel
evaporated generally increases in proportion to the amount of ethanol
added to the base fuel."

Feel free to post up any scientific article that backs up your statement.

The TL : DR version-
"At a given mid-range temperature (e.g., 200 degrees F), the percent of fuel evaporated generally increases in proportion to the amount of ethanol added to the base fuel." - The American Petroleum Institute

Science.

 

[J1000]

I'm the only one on this forum with a fuel temperature gauge and an ethanol percentage gauge. Pump gas 85 octane boils around 110F at 6000 ft MSL. 30% ethanol mix doesn't boil even at 125F and 10,000ft MSL. Sure I guess I could copy paste someone else's work but I'll leave that up to you I'm going to go wheel in the mountains instead.