What grade of gas do you run?

yellow3.8track · May 14, 2011

The salesman told me to just run regular unleaded in my 3.8 coupe.

Does anyone else here run plus or premium? If so do you see any difference in gas mileage or power/responsiveness?

In my previous cars I have seen differences in how the cars run when I run different grades of gas, though in one it made no difference.

My 73 Laguna had to have premium or it lost power and mpg they way I drove it.

My 81 Z28 didn't care what grade I ran in it (or what brand).

My 86 IROC Z28 has to have premium or the mpg drops off and it even particular about the brand of gas (after 2 fill ups on Mobil gas the engine dies when you let up on the gas pedal).

I'm thinking about working my way up through plus to premium in the coupe while watching mpg to see if it makes any difference and was just curious if someone else had done the same.

ifonline · May 14, 2011

Ungh. The grade of fuel in no way enhances performance, horsepower, or fuel economy. That myth really, really needs to be put to rest. Engines are designed to run on a certain grade of fuel. If the engine runs on regular, use regular. Putting premium fuel in an engine designed to run regular won't help.

There are certain exceptions, such as when an engine is capable of identifying the grade of fuel being used, but typically there is absolutely no benefit to increased octane in a regular engine. Only engines designed for higher octane fuels need to run the higher octane fuels. All others... you're wasting money.

homeofstone · May 14, 2011

ifonline said:
Ungh. The grade of fuel in no way enhances performance, horsepower, or fuel economy. That myth really, really needs to be put to rest. Engines are designed to run on a certain grade of fuel. If the engine runs on regular, use regular. Putting premium fuel in an engine designed to run regular won't help.

There are certain exceptions, such as when an engine is capable of identifying the grade of fuel being used, but typically there is absolutely no benefit to increased octane in a regular engine. Only engines designed for higher octane fuels need to run the higher octane fuels. All others... you're wasting money.

Ditto

Vince2 · May 15, 2011

So the eight cyl. Genesis "senses" when premium gasoline is present and adjusts (changes valve timing?) to increase power?

Gurkha · May 15, 2011

Vince2 said:
So the eight cyl. Genesis "senses" when premium gasoline is present and adjusts (changes valve timing?) to increase power?

That is correct as far as I know.
In the 3.8 it should not make a difference as there are no published differences.

mikeyscislo · Jun 7, 2011

There has to be a link between octane and hp, I'm just not a well-versed engineer so I can't tell you what it could be

however, personal preference, the first car I bought with my own money was a 02 WRX, ever since I haven't put anything under 92 in my cars.

jazzypikai · Jun 15, 2011

I have a 3.8 Track and I still just use the regular. With that its about 306 hp. When you use premium, I think the hp jumps to something like 314. Not really a big difference when your driving the car.

yellow3.8track · Jun 15, 2011

Well, I've been running "plus" in my car now for a couple/three weeks and when I filled up this morning the in town gas mileage was 22.9. Not bad for the way I drive.

A few more weeks of "plus" and then I'm going to premium. I just want to make a couple of highway trips first to see how it does there.

yellow3.8track · Jun 22, 2011

Last fill up on "plus" grade unleaded was 23.6 mpg in back and forth to work, shopping, just running around town. Heck, my wife's Ford Fusion with the 2.5 liter 4 cylinder is only getting 24 mpg around town. And it doesn't begin to run like my 3.8 Track.

A few more weeks of "plus" grade and road trip and I'll start the move on up to premium grade gas and see how that works out.

I've got 2400 miles on the car already (in about two months).

snj1013 · Jun 23, 2011

Vince2 said:
So the eight cyl. Genesis "senses" when premium gasoline is present and adjusts (changes valve timing?) to increase power?

Being an engineer, I would assume the opposite to be true. I would assume that the engine would be monitoring "knock sensors" and would retard timing to decrease power when running regular fuel.

As others have noted, run the fuel recommended in your owner's manual. Running premium when the engine isn't designed for it, will get you no more performance (neither MPG, nor HP) and will only lighten your wallet.

yellow3.8track · Jun 24, 2011

filled it up again this morning. 23.6 mpg again. Need to make that road trip here in a week or so to see if the highway mileage goes up as well.

running around town mpg was around 21 using unleaded.

Not bad for a car rated for 17 mpg in town driving.

I'm still happy, especially considering how hard I put my foot in it sometimes.

CWO_Maddog · Jun 28, 2011

I've seen recently where new cars are able to detect knocks in an engine, and in an effort to prevent damage, a small adjustment is made. If the desired results are not achieved, the fuel control will drop down to a low octane "table." This usually happens when an engine which requires premium fuel is now burning a lower octane.

yellow3.8track · Jun 28, 2011

CWO_Maddog said:
I've seen recently where new cars are able to detect knocks in an engine, and in an effort to prevent damage, a small adjustment is made. If the desired results are not achieved, the fuel control will drop down to a low octane "table." This usually happens when an engine which requires premium fuel is now burning a lower octane.

As far back as the early 80's (some) cars had knock sensors in the engine block. When a "knock" condition was detected the computer reduced timing advance to help reduce/get rid of the spark knock.

yellow3.8track · Jul 3, 2011

Well, Friday morning the fill up calculated out to only 22.986 mpg. Off just a little from the previous 2 fill ups. Still way better than the car is rated for.

yellow3.8track · Jul 4, 2011

Filled up this morning and ran it through the carwash. Only 22 mpg this morning.

yellow3.8track · Jul 17, 2011

First road/highway trip with "plus" gas. Even with the car loaded down with my 2 days worth of clothes, my wife's 5 days worth of clothes, and my recreational toys for the weekend in the mountains - and having the cruise control set no less than 72 and no more than 77 mph I got 28.5 mpg on the 260 miles I drove between fill ups on the way back to the house today. Filled up before I left, filled up when I got a couple miles from the house.

Franknspeed · Jul 20, 2011

regular mostly (87), but it does feel a lot quicker with premium.
Gas mileage didn't change, I get between 26 and 28 mpg in daily driving (backroads city mix). Thats not playing around much, though.

yellow3.8track · Jul 30, 2011

Second partial fillup with premium. 104 miles on 4 gallons, or 26 mpg back and forth to work, up to the mall, to the credit union, out for a milk shake, etc.

Right now that's two more mpg than my wife's 2010 Ford Fusion with the 2.5 liter 4 cylinder and 6 spd. automatic.

If it keeps up, I'm a happy camper.

yellow3.8track · Aug 4, 2011

Well, fill up yesterday only got me 21 mpg. Still city driving????

I'm going to put a notebook in the glovebox and start keeping track of the brand of gas and the location of the station as well as the mpg.

When I first got my IROC I noticed if I got gas at one particular station (Chevron near my house) my mpg always dropped from the 20/21 mark down to 17 or 18 mpg. I stopped buying gas there. Don't know what the problem was, I just quit buying gas there. I also found out that the car didn't like Mobil gas. After 3 fill ups in a row from the local Mobil station my IROC would start shutting off when I stopped at stop lights, stop signs and sometimes would even die while going down the road if I let up on the gas suddenly. It took a couple fill ups of Wawa gas with fuel injector cleaner to straighten things out again.

Milkmaster · Aug 13, 2011

The owner's manual says that you can use regular fuel, and my 3.8 runs fine on it.

That being said, the addition of 10% ethanol in a great deal of areas reduces your MPG. Make sure you are buying comparable fuels with or without alchohol added when buying fuel. Look at what the pump actually says when you buy it. Alcohol content will effect your MPG much more than just the octane rating.

Non-alchohol gas cost more, runs my MPG up about 1.5, but is not as readily available in TN. The money works out about the same in the end, so what's the point.

What grade of gas do you run?

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