Regular vs. Premium Unleaded Gasoline.

[stchman]

I had a discussion with someone the other day and we got on the topic of 87 vs. 93 octane gas.

He said that he uses premium in all his cars as the engine will last longer. What a bunch of [censored].

I told that if the manual does not state to use premium, then its use is at best a waste of money.

He said that his cars "feel" better when they run premium. Sounds like the placebo effect has kicked in.

A few months ago I tried running a couple of tanks of 93 in my Silverado and guess what, no change in mileage or power feel. All I did was waste ~$7 a tank.

He did not want to believe me that octane is just a combustion inhibitor. Oh well.

 

[BISCUT]

He's blowing money out the window with no gain! TOOL!

 

[badtlc]

premium gives me better MPGs on my skyactiv but hasn't shown any benefits on my escape. I think it varies by use and vehicle.

 

[fusion0389]

I notice MPG gains on my Fusion Sport when I use premium, nothing ridiculous but its definitely repeatable. My best power\MPG gains are when I use non-ethanol gasoline.

 

[NMBurb02]

Maybe he has ALOT of carbon buildup in the combustion chambers, increasing compression and therefore making something higher than 87 (but maybe not all the way up to 93) necessary/beneficial?

 

[Cujet]

It varies wildly, by vehicle.

My 2003 Jaguar X-Type has horribly uneven acceleration on 87 octane regular. But, performs normally on 93 octane.

The reason is that the knock sensor pulls timing erratically when using 87 octane.

The new Ford Focus ST Ecoboost is rated for regular, as is my 3.5L Ecoboost F150 and my 2009 F150 with 5.4L. All 3 vehicles experience a power boost on 93 octane. Dyno reports show the Focus gains 9HP, and both F150's gain about 10 foot pounds of torque and 20HP on 93.

http://www.f150forum.com/f38/ecoboost-has-385hp-430lb-ft-premium-fuel-201718/

A Prius won't likely gain anything with Premium. Same goes for many vehicles with low compression or modest tuning.

 

[hypervish]

I get more power and better mpg on 93 octane in both my RX300 and ES300. However both car's are tuned for high octane fuel.

I can run lower octane in both and not have a problem, however mpg will suffer along with power.

 

[DB_Cooper]

I would think it would depend on the knock sensors, fuel management systems and how sophisticated the software is. Some will run the timing advance up with high test fuel..and you may feel some improvement in performance/economy.

Had a 2007 Subaru 2.5 with knock sensors that did not care what fuel..the engine just performed the same at the same MPG.

Have and Audi with knock sensors that definitely loves premium fuel..and can run regular too.

Have a 86 Porsche 911..never ran regular fuel in it..no knock sensors.

 

[SwampSurvivor]

I tried to run 93 ethanol free in my Cherokee to see if I got better gas mileage from not having ethanol. Gas mileage went down. Some engines can't take advantage of it.

My parents Focuscape recommends premium. I have been trying to get them to run premium but they won't.

 

[SevenBizzos]

Yes, it varies by car. Our Sonata gets somewhere around 1-1.2mpg better on 89 (after keeping track for 70k miles). Some say you can squeeze a little more for going up more. Our '04 Elantra for sure ran better with a higher octane.

On the flipside the V6 Accords have reduced HP (like 4 or 5) when they run high octane gas.

I used to try to use 89 and above when the price difference was $.10 abov 87, but now it's $.20 - $.2 5(and sometimes more), which makes "premium" $.40 - $.50, so the pricing structure has made me really slow down on it.

I'd say you'd have to run at least 5 tanks of it do even make a guess if it makes a difference on your car.

 

[stchman]

I still maintain that if the manufacturer recommends 87 octane, going to 93 will net you no benefit.

 

[sciphi]

Originally Posted By: stchman
I still maintain that if the manufacturer recommends 87 octane, going to 93 will net you no benefit.


Not exactly true. My turbocharged Cruze recommends 87. It runs noticeably smoother and with better power and MPG on 93 octane. Our Fit does not care either way.

 

[stchman]

Originally Posted By: sciphi
Originally Posted By: stchman
I still maintain that if the manufacturer recommends 87 octane, going to 93 will net you no benefit.


Not exactly true. My turbocharged Cruze recommends 87. It runs noticeably smoother and with better power and MPG on 93 octane. Our Fit does not care either way.


Forced induction engines can have some benefit of using higher octane fuel in hot weather, especially those with small displacement. For naturally aspirated engines, this is not the case.

 

[randomhero439]

Originally Posted By: SevenBizzos


On the flipside the V6 Accords have reduced HP (like 4 or 5) when they run high octane gas.


My V6 Accord runs better on 93 octane. There is even an article written about the engine stating that it makes +10bhp and +10tq on premium fuel instead of regular. The 3.0L is 10.0:1 compression btw.

USA Today discusses new Accord with Honda engineers

Quote:
The V-6 engine storms. It produces less leap at low speed than you get from the thick torque in the Nissan Altima but otherwise is glorious. It revs so fast to the redline that it'll beat your reflexes, leaving you scrambling to shift the manual transmission to the next higher gear in time.
Torque is the key to quick starts from dead stops. Accord's 240-hp V-6 is rated 212 pounds-feet of torque. Altima's 240-hp V-6 is rated 246 lbs.-ft.

The Accord V-6 ratings assume regular-grade fuel, and Honda will market it as a regular-fuel engine. But — pssst — it's good for another 10 hp and 10-plus lbs.-ft. on premium, acknowledges V-6 engineer Asaki.

 

[eljefino]

We need to know the car. Knock sensors have evolved from emergency engine protectors to a regular part of the feedback loop.

For marketing or CAFE reasons they'll recommend 87. Some ads will claim "peak HP" with fine print that it's on 91. (A dodge comes to mind.)

A car in knock retard sure doesn't feel smooth. The real test is a double-blind of having a 3rd party buy fuel for the car and not saying for a month what it is.

 

[mattwithcats]

Gas companies got you coming and going, and they are laughing each way...

Higher octane fuel has fewer calories than lower octane, hence less energy per gallon...

In a car that does not require premium, putting premium in just wastes money and results in lower MPG....

I run 85 octane when I can get it...

 

[SevenBizzos]

Originally Posted By: randomhero439
Originally Posted By: SevenBizzos


On the flipside the V6 Accords have reduced HP (like 4 or 5) when they run high octane gas.


My V6 Accord runs better on 93 octane. There is even an article written about the engine stating that it makes +10bhp and +10tq on premium fuel instead of regular. The 3.0L is 10.0:1 compression btw.

USA Today discusses new Accord with Honda engineers

Quote:
The V-6 engine storms. It produces less leap at low speed than you get from the thick torque in the Nissan Altima but otherwise is glorious. It revs so fast to the redline that it'll beat your reflexes, leaving you scrambling to shift the manual transmission to the next higher gear in time.
Torque is the key to quick starts from dead stops. Accord's 240-hp V-6 is rated 212 pounds-feet of torque. Altima's 240-hp V-6 is rated 246 lbs.-ft.

The Accord V-6 ratings assume regular-grade fuel, and Honda will market it as a regular-fuel engine. But — pssst — it's good for another 10 hp and 10-plus lbs.-ft. on premium, acknowledges V-6 engineer Asaki.



Here's a little data from a source that actually tested the V6:
http://www.caranddriver.com/features/regular-or-premium-test-results-page-2

I think we'll agree C&D has a little cred.
"The Accord took a tiny step backward in power (minus 2.6 percent) and performance (minus 1.5 percent) on premium fuel"

 

[BISCUT]

Originally Posted By: hypervish
I get more power and better mpg on 93 octane in both my RX300 and ES300. However both car's are tuned for high octane fuel.

I can run lower octane in both and not have a problem, however mpg will suffer along with power.


Higher compression ratio than the Prius.

 

[fdcg27]

Originally Posted By: Cujet
It varies wildly, by vehicle.

My 2003 Jaguar X-Type has horribly uneven acceleration on 87 octane regular. But, performs normally on 93 octane.

The reason is that the knock sensor pulls timing erratically when using 87 octane.

The new Ford Focus ST Ecoboost is rated for regular, as is my 3.5L Ecoboost F150 and my 2009 F150 with 5.4L. All 3 vehicles experience a power boost on 93 octane. Dyno reports show the Focus gains 9HP, and both F150's gain about 10 foot pounds of torque and 20HP on 93.

http://www.f150forum.com/f38/ecoboost-has-385hp-430lb-ft-premium-fuel-201718/

A Prius won't likely gain anything with Premium. Same goes for many vehicles with low compression or modest tuning.


I see the same thing with my old BMW.
The car is fine on 87 until you really want to use it, as in two lane passing.
You can then really feel the timing being cycled between retard and advance.
The car might get better mileage with premium, althought the difference isn't great.

 

[y_p_w]

My parents drive a 2001 Camry V6. The owner's manual says that 87 octane is fine, but that the engine will be capable of better performance (and mileage?) with 91 octane. I guess it's all in the way it's marketed.