Super Unleaded test compared to Regular Unleaded:

Alwaysforward · Dec 23, 2014

I concluded phase one of my test. I strictly use Mobil gasoline for this test and thought I would share my findings.

Car: 5.0 Ultimate RWD

Conditions: Sport mode 24/7 in strictly city driving of one full tank of each fuel type (Super Unleaded and Regular Unleaded).

Findings:

Burned 1 full tank in Sport Mode using Mobil Super Unleaded and got the following fuel mileage:

Onboard computer - 18.90 MPG
Calculated mileage - 17.40 MPG

Burned 1 full tank in Sport Mode using Mobil Regular Unleaded and got the following fuel mileage:

Onboard computer - 16.6 MPG
Calculated mileage - 15.22 MPG

I can drive 348 miles on a tank of Super Unleaded -vs- 304.4 miles using Regular Unleaded. This equates to an additional cost of $7.50 more Regular Unleaded fuel to drive the additional 43.6 miles I got with Super Unleaded.

Factor in the added cost per gallon (Super vs Regular) of $7.20 per tankful, I save .30 cents per tank using Super Unleaded -vs- Regular Unleaded.

I just refilled the tank with Super again and will drive using same conditions (Sport Mode 24/7 & city driving) and will report back. Once I complete that test I will do it all over again using ECO mode using both types of fuels to see what the out come is.

OneFunGenesis · Dec 23, 2014

sub'd. This is awesome because nobody believes I get better MPG from Premium even though I have the data to back it up.

Keep up the good work!

Alwaysforward · Dec 23, 2014

Although the savings is minute, the added benefit of the cleaner fuel burning you get with Super Unleaded is what I like most.

DavidA5913 · Dec 23, 2014

I wonder what using mid-grade results would be like?

homeofstone · Dec 23, 2014

Lets see a comparison of 0-60 times with reg. vs. premium. 0-60 is important to me in avoiding accidents in the ATL area. I use premium anyway but it would be good to know the difference.

Alwaysforward · Dec 23, 2014

homeofstone said:
Lets see a comparison of 0-60 times with reg. vs. premium. 0-60 is important to me in avoiding accidents in the ATL area. I use premium anyway but it would be good to know the difference.

Report back your test. I would be interested in that as well.

ksoze · Dec 23, 2014

homeofstone said:
0-60 is important to me in avoiding accidents in the ATL area.

How bad is it in the Peach State that one needs to quickly exit a situation from a standing start - aside from bank robbing or drag racing, can't think of where this would makes sense

PMCErnie · Dec 23, 2014

Even though one of these guys just died, I think the Car Talk guys are more credible on this subject.

http://www.cartalk.com/content/premium-vs-regular-0

Then there is Edmunds...

http://www.edmunds.com/fuel-economy/to-save-money-on-gas-stop-buying-premium.html

Car and Driver knows a few things about cars too.

"Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price."

http://www.caranddriver.com/features/regular-or-premium

homeofstone · Dec 23, 2014

ksoze said:
How bad is it in the Peach State that one needs to quickly exit a situation from a standing start - aside from bank robbing or drag racing, can't think of where this would makes sense

Not so much standing start but from 35 to 70 is important. I have avoided several crashes by accelerating out of the way or pass a car pulling out in front of me with not enough distance to stop.

Schindawg · Dec 23, 2014

I don't have any hard data, but up here in the Northwoods you can get non-oxygenated 91 octane fuel at some stations for boats, snowmobiles, etc. No ethanol at all in this stuff. I filled up GMC Savana conversion van before a long trip and put nearly 500 miles on the tank before needing to refuel. I've never gone that far before on either regular unleaded or super unleaded with ethanol. I think it comes down to there being more energy in petroleum based fuel than in ethanol. I don't have an E85 vehicle, but while the fuel is cheap, the gas mileage drops significantly for the same reason.

homeofstone · Dec 23, 2014

PMCErnie said:
Even though one of these guys just died, I think the Car Talk guys are more credible on this subject.

http://www.cartalk.com/content/premium-vs-regular-0

Then there is Edmunds...

http://www.edmunds.com/fuel-economy/to-save-money-on-gas-stop-buying-premium.html

Here is a good article on octane. http://www.economist.com/blogs/babbage/2012/09/octane-ratings

I question some of the Cartalk myth statements regarding engines that require premium.

Edmunds does not take into account super high performance cars that require 91 or above octane. A lot of premium gas in my area is 92 or 93 octane. The Genesis engines can run fine on regular. My BMW would have a spark knock with regular and my Mercedes also is sluggish and has occasional spark knock. So saying regular is fine for all passenger car engines is not necessarily true.

homeofstone · Dec 23, 2014

PMCErnie said:
Even though one of these guys just died, I think the Car Talk guys are more credible on this subject.

http://www.cartalk.com/content/premium-vs-regular-0

Then there is Edmunds...

http://www.edmunds.com/fuel-economy/to-save-money-on-gas-stop-buying-premium.html

My E63 owners manual states "only refuel with unleaded premium grade gasoline as this avoids damage to catalytic converter" and "only refuel with unleaded premium gasoline with a specified minimum octane of 91" and " to ensure longevity and full performance only premium grade unleaded gasoline must be used"

So I don't think the so called myths apply to all cars.

JBoogie · Dec 23, 2014

DavidA5913 said:
I wonder what using mid-grade results would be like?

+1
I only use the midgrade.

jimb100 · Dec 24, 2014

Thanks for running the test.

I've done this test myself with other cars and have gotten the same results. Better gas mileage with premium has always made up for the extra cost.

The performance benefit is a nice bonus.

Frankly, I don't think there is much of a "cleaner engine" benefit. Its been a long time since I heard of anyone having valve problems that were a result of using regular.

PMCErnie · Dec 24, 2014

I edited my post above to add Car and Driver's thoughts on premium vs regular gas. Basically they say you are wasting money to buy more octane than your engine needs to run smoothly. For most folks, regular does the job at the lowest price per mile.

EXBMWGUY · Dec 24, 2014

jimb100 said:
Thanks for running the test.

I've done this test myself with other cars and have gotten the same results. Better gas mileage with premium has always made up for the extra cost.

The performance benefit is a nice bonus.

Frankly, I don't think there is much of a "cleaner engine" benefit. Its been a long time since I heard of anyone having valve problems that were a result of using regular.

With top tier fuel, I don't believe there is any data that suggests premium fuels are cleaner or run cleaner than regular unleaded. Various marketing promotions want us to believe premium is cleaner, but marketers want us to believe a lot of things.

amartz · Dec 24, 2014

Well, we can believe the so-called "experts", or we can believe real world data. I know which I go with. Thanks Alwaysforward, looking forward to the rest of your test. Even if it costs me $0.30 more a tank instead of less, I think I could live with that!

ep010835 · Dec 24, 2014

Thanks. Excellent discussion by all. The links are especially appreciated.

PMCErnie · Dec 24, 2014

Scientific American thinks it's eccentric to put premium in your tank.

http://www.scientificamerican.com/article/fact-or-fiction-premium-g/

Forbes would agree.

http://www.forbes.com/sites/tombarlow/2011/07/12/do-you-really-need-premium-gas/

homeofstone · Dec 24, 2014

PMCErnie said:
Scientific American thinks it's eccentric to put premium in your tank.

http://www.scientificamerican.com/article/fact-or-fiction-premium-g/

Forbes would agree.

http://www.forbes.com/sites/tombarlow/2011/07/12/do-you-really-need-premium-gas/

I just read the above articles. The two above articles agree that some high performance engines require premium. Its best to read the car's manual and if it says premium recommended then regular is ok. BUT if the manual says premium REQUIRED then that is what it means. Forbes uses the example of the BMW 6 series of premium required. Scientific America states that some high performance sports cars will knock with regular gasoline. I also don't get the fuss over the maybe few hundred dollars a year more spent for premium when the car cost over 40k or maybe over 70k.

Super Unleaded test compared to Regular Unleaded:

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