AAA's Premium vs. Regular Gas Tests

[camrydriver111]

AAA tested the old premium vs. regular question for cars that recommend, but do not require premium. Both regular and premium had 10% ethanol in their tests BTW.

https://newsroom.aaa.com/2017/12/dont-fueled-premium-not-always-worth-price/

Quote:
Fuel economy for test vehicles averaged a 2.7 percent improvement. Individual vehicle test result averages ranged from a decrease of 1 percent (2016 Audi A3) to an improvement of 7.1 percent (2016 Cadillac Escalade).

Horsepower for test vehicles averaged an increase of 1.4 percent. Individual vehicle test result averages ranged from a decrease of 0.3 percent (2016 Jeep Renegade) to an improvement of 3.2 percent (2017 Ford Mustang).


Full Report https://newsroom.aaa.com/wp-content/uplo...ort-FINAL-2.pdf

Interestingly for the Audi there was more mpg with regular gas, however the engine produced a "harsh audible engine knock in road driving using regular gasoline" so the engine was not able to prevent knock.

I was looking at the charts at the back of the report and a lot of the cars had a lower catalyst temperatures with premium gas. How would premium gas lower the catalyst temperature?

 

[skyactiv]

We have a thread on here where people bash premium gas once a week. The auto makers want to make engines that require premium gas.
The skunk works engine designs the auto makers are working on depend on premium gas and is why GM-and others want a high octane standard.
The recent relaxing by the EPA doesn't mean the auto makers are giving up on future engine development.
We need better gas engines for them to survive unless you wanna limit your only choice to hybrids.

 

[Danno]

Originally Posted By: camrydriver111
I was looking at the charts at the back of the report and a lot of the cars had a lower catalyst temperatures with premium gas. How would premium gas lower the catalyst temperature?

I suspect the engines dump in more fuel to keep knock under control with regular, causing more fuel to be burned and more heat in the cat.

 

[Danh]

Originally Posted By: Danno
Originally Posted By: camrydriver111
I was looking at the charts at the back of the report and a lot of the cars had a lower catalyst temperatures with premium gas. How would premium gas lower the catalyst temperature?

I suspect the engines dump in more fuel to keep knock under control with regular, causing more fuel to be burned and more heat in the cat.


And more fuel dilution of engine oil...

 

[CT8]

Originally Posted By: Danno
Originally Posted By: camrydriver111
I was looking at the charts at the back of the report and a lot of the cars had a lower catalyst temperatures with premium gas. How would premium gas lower the catalyst temperature?

I suspect the engines dump in more fuel to keep knock under control with regular, causing more fuel to be burned and more heat in the cat.
Higher octane allows more timing advance.

 

[dblshock]

Just filled with E091 $3.39 vs. $2.92 E1087

 

[PimTac]

Originally Posted By: Danh
Originally Posted By: Danno
Originally Posted By: camrydriver111
I was looking at the charts at the back of the report and a lot of the cars had a lower catalyst temperatures with premium gas. How would premium gas lower the catalyst temperature?

I suspect the engines dump in more fuel to keep knock under control with regular, causing more fuel to be burned and more heat in the cat.

And more fuel dilution of engine oil...

I agree with this. The engine in my Mazda has a 13:1 compression ratio yet is rated to run on 87. I have been using Shell 92 since the initial tank and the response plus the fuel economy has gone up. I notice the effect more on uphill drives.

 

[SHOZ]

My Gen Coupe is advertised, or was, to get 7 more HP using premium vs the normal 87 octane.

 

[WylieCoyote]

Even the most sensitive butt dyno isn't going to be able to pick up on a 3hp gain, so performance really isn't my concern when I fill up. I just feel better doing whatever I can to prevent LSPI.

Peace of mind can be expensive.

 

[MCompact]

When I go car shopping the grade of fuel required is never a consideration; I simply use what the manufacturer recommends and enjoy the drive...

 

[hatt]

Originally Posted By: WylieCoyote
Even the most sensitive butt dyno isn't going to be able to pick up on a 3hp gain, so performance really isn't my concern when I fill up. I just feel better doing whatever I can to prevent LSPI.

Peace of mind can be expensive.
My butt Dyno has indicated my truck holds gears better with the 93/87 mix I've been doing for a few weeks.

 

[grampi]

I wouldn't mind vehicles so much that require premium fuel if the price spread between regular and premium wasn't so much...how 'bout we go back the mid grade being 10 cents more than regular, and premium being 10 cents more than the mid grade? Today's price spread is ridiculous...

 

[Triple_Se7en]

The value of 10 cents back then has now risen to qualify the price jump spread now. That 40 cent spread foreach gas grade today is the same value as 10 cent back in the 60s and 70s.

 

[nthach]

I once filled up a older Lexus LS400 with regular, and there was quite a difference. The car knocked if you went beyond 1/8th throttle pulling away and it just felt like it didn't have power. This was a engine designed in the 1980s using Denso's take on Bosch's Motronic engine controls - so timing or ignition could have been pulled back but there was still knock.

I think I put in some premium in the parent's Sienna and I didn't feel anything - while the misfire monitors are always running and the ECU/PCM is always listening to the knock sensors, it might take clearing of the adaptives and a drive on a full tank of premium to get the the hotter timing tables to kick in.


If Honda specified premium in their 1.5T in the Accord/Civic/CR-V from the get-go, they could have avoided the fuel dilution debacle.

 

[Yah-Tah-Hey]

I use the 91 octane because it is the only fuel available without ethanol. Hope my next door neighbor doesn't find out as he works for ADM and they make millions of gallons of grain alcohol.

 

[Patman]

Originally Posted By: grampi
I wouldn't mind vehicles so much that require premium fuel if the price spread between regular and premium wasn't so much...how 'bout we go back the mid grade being 10 cents more than regular, and premium being 10 cents more than the mid grade? Today's price spread is ridiculous...


It's even worse in Ontario, at many stations they charge about 14 cents PER LITER more for midgrade and 22 cents per liter more for premium. Convert that to gallons and that means a 53 cent per gallon price jump for midgrade and an 83 cent per gallon spike for premium. Add that to the already outrageous price we pay at the pumps even for regular, and it's no wonder people up here have a hard time making ends meet....

 

[Jarlaxle]

Originally Posted By: MCompact
When I go car shopping the grade of fuel required is never a consideration; I simply use what the manufacturer recommends and enjoy the drive...


Until you are on a road trip and discover you cannot GET premium, there is none to be had at any price! Been there and done that.

 

[MCompact]

Originally Posted By: Jarlaxle
Originally Posted By: MCompact
When I go car shopping the grade of fuel required is never a consideration; I simply use what the manufacturer recommends and enjoy the drive...


Until you are on a road trip and discover you cannot GET premium, there is none to be had at any price! Been there and done that.


It hasn't happened to me yet; maybe I'm just lucky.

 

[Tahoe4Life]

Originally Posted By: MCompact
Originally Posted By: Jarlaxle
Originally Posted By: MCompact
When I go car shopping the grade of fuel required is never a consideration; I simply use what the manufacturer recommends and enjoy the drive...


Until you are on a road trip and discover you cannot GET premium, there is none to be had at any price! Been there and done that.


It hasn't happened to me yet; maybe I'm just lucky.


In my neck of the woods stations sometimes run out of regular. Never premium. I barely see anyone use premium anymore. My buddy has 6.2 Yukon Denali and a Escalade and both run perfectly fine on 87 regular.

 

[Jarlaxle]

No, not out of premium. I have seen stations that DO NOT SELL IT. Saw one in Alabama on vacation...had 87 octane E10, and 87 octane no ethanol, that's it! Saw two in Maine that had only 87 octane and diesel fuel. Saw many in rural areas of the Midwest with only 87 or 87 and 89.

That was one thing I was concerned about with my Sportster...it calls for (and absolutely requires, especially in hot weather) premium gas.