89, 91 or 93 Octane

[Pahaska]

I run only 87 octane. I drove 258 miles this morning from NE of Dallas to SW of Austin, all limited access at 70 to 80 mph on I-635, I-20 and I-35 with just one stop for breakfast. I know the mileage monitor may read a bit on the high side, but when I stopped at the first traffic light near home, the monitor read 29.9.

This is my 4th trip of any length and the mileage as shown by the monitor has improved each time.

The thing I love most is the instant acceleration when I have to jump into the left lane to get around slow traffic. Just touch the pedal and the speedo jumps.

 

[Bear]

From the manual: 4.6 engine
Your new vehicle is designed to use only
unleaded fuel having a pump octane
number ((R+M)/2) of 87 or higher.

For improved vehicle performance, premium
unleaded fuel with a Pump Octane
Rating of 91 (Research Octane Number
95) or higher is recommended.

I use 91.

 

[Bear]

Postscript: I also don’t get the mileage that everyone else seems to get. Using the odometer and gas receipts, I get 15-16 city driving and 24-25 on the highway. Gentle driving.

 

[Nabber]

In Iowa, 91 octane is used almost exclusively. It's the "cheap stuff" here as it contains 10% ethanol. Corn is of no short supply here.

 

[scottdk]

Postscript: I also don’t get the mileage that everyone else seems to get. Using the odometer and gas receipts, I get 15-16 city driving and 24-25 on the highway. Gentle driving.

Not sure how many miles you have on your car, but I didn't see MPG increases ttle moruntil I had about 8,000 miles or a little more on my car. Best I could do brand new on highway was 26, now my best has been 30.2.

 

[Stwood]

Stwood update (started this thread on 9/9/09):

Have fueled my 4.6 up with 87 since my first fill and have nothing negative to say (no knocks, acceleration problems ...). Just over 1,500 miles on the rig and I average 17-18 in town and 26 on the highway. As stated previously, I was a long time Saab owner and always put 91 to 93 in my cars with a noticeable performance difference and no knock vs knock. Will not start putting higher octane in my 4.6 unless someone convinces me otherwise. All that I've read thus far, leaves me with 87 all the way.

V8 Genesis vs a V4 Turbo Saab 9-5 Aero and mileage is just a tad lower, but the cost saving on the gas more than makes up for it!

Nice work on the V8 Hyundai!

 

[ffb13]

stwood

i am considering getting a v6 or v8

i also own a 2000 saab 9.5 aero which has been great .i use it for trips to florida 4 times per year (hate flying commercial ) and get 30 to 32 mpg at plus 80 mpg in many areas with an overall ave of 69 mph).

considering the v6 due to its lower weight and mpg,but based on what i read here the v8 may be a better engine from a tech point of view. and the mpg is not that bad or different from the v6 ??

anyhow will post elsewhere about some questions that i have

 

[ADEN]

We don't have 93 in CA, you must live somewhere in the East coast. I have been running 87 for 4 months, and thought I would give it a try to 91. I have noticed the engine is smoother, throttle response is better and gas milage slightly improved. Is it a big difference? No.
If I were you I would use 87 or 89 what ever is cheaper and drive it under 4000 rpm for the first 1000 miles. Then I would change the oil to a good synthetic and 93 and then go nuts. (of course if you leased it, go nuts now, it's basically a rental.)

A somewhat related question: does the fuel economy improve after the first few hundred miles? Irrespective of the grade of gas I use, my 2010 V8 (July '09 manufacture) gets around 15 MPG in local diriving. I am at ~ 900 miles now.

thanks,

 

[Mark_888]

A somewhat related question: does the fuel economy improve after the first few hundred miles? Irrespective of the grade of gas I use, my 2010 V8 (July '09 manufacture) gets around 15 MPG in local diriving. I am at ~ 900 miles now.

thanks,

Usually it does improve once the rings are seated. Maybe a few thousand miles.

 

[Mark_888]

stwood

i am considering getting a v6 or v8

i also own a 2000 saab 9.5 aero which has been great .i use it for trips to florida 4 times per year (hate flying commercial ) and get 30 to 32 mpg at plus 80 mpg in many areas with an overall ave of 69 mph).

considering the v6 due to its lower weight and mpg,but based on what i read here the v8 may be a better engine from a tech point of view. and the mpg is not that bad or different from the v6 ??

anyhow will post elsewhere about some questions that i have

The highway mileage difference between V6 and V8 is 2 MPG according to the EPA. I have no reason to question that. Most people get more than the rated mileage on both V6 and V8, probably because the Genesis gets better mileage at 65-70 than it does at 55, due to the fact that both trannys have 2 overdrive gears, and 6th gear is very tall.

The Hyundai Tau V8 is technologically advanced, but it also has a few quirks, probably because it is so new.

Unless you are frequently hauling 4 large adults or other heavy loads, the V6 is plenty of power for just about everyone.

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[wallymn]

In Iowa, 91 octane is used almost exclusively. It's the "cheap stuff" here as it contains 10% ethanol. Corn is of no short supply here.

but it is hard to find 93 when I go down there....

 

[BorregoV8]

I have tried them all 87 89 92. The Borrego's acceleration is sluggish on regular 87 but runs mostly OK. On 92 its a rocket ship but sometimes seems to run a bit rich you can smell it in the exhaust. Eighty Nine mid grade has a bit less pep than the 92 but better than 87 and otherwise runs fine. I think I'm going to run 89 from now on.

 

[rmhockman]

R M Hockman
4.6 silver with black & tech.

This is my second Genesis having had a 3.8 for nearly 2 years. It was an excellent machine but when compared with the V8 it feels and drives like a completely different car!!!!

I have been using mid grade with no discernable loss of power and this engine runs so smooth it amazes me. Changed oil at 2000 miles and using 5w-30 regular grade oil for the present, will move up to synthetic at around 7500 miles.

Have driven a little over 3000 miles and highway mileage, including interstate travel averages in the 30 to 31 mpg range on a consistent basis, around town it is substantally less, of course the 3.8 was a bit more economical.

 

[vegas]

My fuel MPG was NOT hurt by using 87 (R+M/2) Octane. I ran 92 (91-93) for a while, and no difference. (with 87, I can live without the extra 7hp).

What does surprise me though, is that using E10 does not cause me to loose any MPG, compared to non E10. We have a place closeby that advertises Gasoline with NO Ethanol. Costs about 20 to 30 cents more a gallon. I used it for a while, and found no increse in my MPG, so I went back to E10.
In my previous car (an MKZ), using E10 got me 10 to 20% LESS MPG so I'm surprised that there is no decrease with the Genesis.
As I've stated before, the only good thing about E10 (if there is anything good about E10) is that it keeps your injectors and fuel lines clean. No need to get the costly "injection cleaning" done at various places.

There is so much detergent in gasoline that nobody needs to buy injector cleaners, thats an even bigger scam....

Ever pull an injector off any gasoline engine and actually seen the TIP dirty? Doesnt happen.

 

[vegas]

whoops, double post

 

[rmhockman]

Has anyone else compared the differences between 87, 89 or 91 octane and beyond as there must be some advantage to the mid grade over the 87??

For your information my first Genesis was a 3.8 which was driven for nearly 19000 miles and fuel type was not as issue, but let me tell you now that car certainly was no slouch and a first rate interstate cruiser, I traded it solely for the much more powerful V8 upgrade.

The 4.6 that I currently have is of course a much different machine both from a suspension standpoint and with the perfected matched engine transmission combination and surging power.

As for the 4.6 I have tried all of the above mentioned grades over the last 5000 miles or so and really can see no appreciable difference in performance and/or fuel mileage, however it is nearly impossible to make accurate comparisons over the same 230+ miles course that I run on a near weekly basis due to varying weather conditions.

Your comments will be welcomed.

R M Hockman
Du Bois PA
4.6 Genesis With Tech
Silver w/ black

 

[Gambler]

Postscript: I also don’t get the mileage that everyone else seems to get. Using the odometer and gas receipts, I get 15-16 city driving and 24-25 on the highway. Gentle driving.

I get similar numbers to you, comparing "city" and "highway" mileage is highly variable to your location and commute. I actually drive almost completely highway but get 15-16 mpg. Why? My commute is normally bumper to bumper for 20-25 minutes. However, I've gotten as high as 29.9 on 100% road-trip highway driving. So numbers given by others should be taken with a grain of salt.

 

[bradyb]

the ECU is a remarkable unit. It will adapt shift points, timing, etc to adapt to driver as well as environmental factors like heat cold altitude (longitude - latitude HAHAHA) and gasoline oct and fuel quality. very remarkable. now i just wish i could break into it and give it a hot tune and disable the ECS.......

 

[Charlie1982]

Gonna resurrect this thread for a bit, so that I can ask this question: has anyone here dealt with “pinging” (preignition/detonation)? I had it happening recently when I was in second gear, mostly at low RPM/medium-high load conditions, like pulling away from a stop sign. If I would manually shift through the gears, I could keep it from happening by holding in first gear until I got to at least 2000 RPM. (Had a little pinging at high loads in upper gears, but only once or twice.)

The problem seems to have disappeared since my last fill-up, so I suspect it was bad fuel, but I figured I’d ask if anyone else had experienced this problem. And just for the record, I always fill up with clear (non-ethanol) premium, so the octane rating shouldn’t have mattered.

 

[jep604]

My 2014 3.8 is designed for 87 octane and that is all that I use. I use Lucas fuel additive unless I can fill up at a BP station which there is one near my home area and two very close to work.