G37S. Can the MPG improve?

[Looneybomber]

I did a lot of research when buying cars, and figured the G37S, RWD coupe was a good mix of all things I considered – performance, MPG, daily living, kids in the back…yeah it’s a little tight, but they fit.

I’m a conservative driver, and consistently get an average per tank MPG better than the vehicle’s rated HWY MPG. For example, my explorer is rated 18 hwy, I get 20-22 per tank. My friend’s Focus was rated 36 or 38 hwy, I got 43.9, My wife’s old Altima was the same story. I like to think I’m an amateur hypermiler.

So as for my G37, I got the 7AT since it is rated for better mileage than the 6MT. In town, my 30 mile average was 12.7mpg, and my tank average is usually around 23mpg. On the hwy, my best is 27.2mpg and that will include a LOT of driving well under the speed limit, at times doing 40 in a 75 at the tops of hills. My 160 mile, all hwy drive I took, I got 24.5mpg and averaged around 60-65mph...I don't remember the exact speed. What I’m getting at, knowing my history with cars, I expected to get 29-30mpg per tank.

What kind of mods or tuning can be done that guarantees better MPG? I see some folks will put on high flow cats, exhaust, intake, and tune and net a small increase in MPG, maybe 2 or 3. Is this pretty typical? That being said, I was hoping for about a 6-7mpg increase to get me near 30mpg average.

[telcoman]

Have you tried using regular 87 octane?

Telcoman

[Looneybomber]

I've run two tanks of premium and two of regular. No noticeable change, so I've stuck with the cheaper 87 octane.

[telcoman]

That is similar to my one month tests of 91 and 93 after I purchased my previous 06 G35
I saw slightly better results with regular 87 octane.
Outside temperature, humidity and elevation also have an effect on MPG
Keep air filters clean
I replace mine every 8 to 10k miles

Telcoman

[FlipSwitch]

Try an intake. I've noticed 2-3 mpg difference. I'd also stay high octane.

[Looneybomber]

So I've done what I can hypermiling the car. On my way back from work, I pulled out of the gas station and drove 25 miles home. I averaged 27.5mpg at 49.8 mph. It was on roads with 45 or 55mph speed limits. I had two round-abouts, a couple stop signs I ran, and three stop lights in town (still going 45-50mph in town). In all, I came to a complete stop once. I modulated my gas on all the hills - ever so slightly decreasing it as I slowed going up and ever so slightly increasing as gravity pulled me down. I did what I could to keep the MPG bar pegged at 30mpg. It was an exhausting drive and I spent more time looking at the MPG bar than I did the road. On big hills I hit about 70mph at the bottom and 40 at the top, never getting out of 7th gear.

Cruise control on, driving from Lawrence to KC on the interstate at 80mph, I get 20.5mpg on that 30 mile stretch...Maybe its MPG is overrated by a few? seems 14/25 city/hwy is more accurate. I'm around 850ft in altitude, so the air is still fairly dense here. I'd hate to see what my car would get in Denver.

[Kendahl]

I'm about 150 miles north of you in Omaha. My altitude is 1,000 feet and temperatures average 3 degrees colder. I run my 2008 G37S on premium. Lifetime average fuel consumption is 23.6 mpg. Because of the all wheel drive, I would expect your G37 not to do as well.

Temperature has noticeable effect. My best mpg happened during a summer heat wave and the worst during a winter cold snap. On average, winter mpg is a couple lower than summer.

On the highway, speed matters. That best mpg (nearly 30 mpg) occurred during a 350 mile trip on a 90 degree summer night over lightly traveled highways at about 65 mph. Drop the temperature 30 degrees and raise the speed by 10 mph and mpg will drop to 24 or 25.

The rolling resistance of tires matters, too. I have noticed that the car doesn't coast as freely with my current tires, Michelin Pilot Sport Cups, as it did with the OEM Bridgestones. (In every other way, the Michelins are far and I don't regret buying them.)

[Looneybomber]

Yeah, winter gas is pretty crappy. I don't know how they change blends throughout the year, but my MPG always suffers in the winter. I should technically get better performance in the winter since the air is colder and more dense, but the makeup of the gas reigns supreme.

[larsG35]

Since the somewhat debated shift to selling gas by the kilogram (or other weight) hasn't happened yet, you actually get better gas in the winter as well. Generally speaking (as the composition of gasoline will very somewhat), gas purchased at 0 degrees C will have 5% more energy (per volume) than gas purchased at 30 degrees C. (32F vs 86F).

This is due to the increase of density when a liquid is cooled. Since it's stored underground and temperature fluxuations are less extreme, maybe it's more like 2.5% summer vs winter.

Even with this advantage, most people get worse MPG in the winter due to friction. Engines that run richer longer to reach optimum operating temperatures and more viscous lubrication oil (engine drivetrain, and transmission fluid) sap much more than this 2.5% extra.

Moral of the story. Buy your gas in the winter and use it in the summer!

Personally I tend to get very similar MPG in the winter vs summer,

Lars

[Starter]

Yeah, winter gas is pretty crappy. I don't know how they change blends throughout the year, but my MPG always suffers in the winter. I should technically get better performance in the winter since the air is colder and more dense, but the makeup of the gas reigns supreme.

Contrary to the post just above this one, that's not what causes bad gas mileage.
It's the Federally mandated use of more ethanol in the gas. Ethanol yields less energy than gasoline hence it takes more fuel to do the same work. That's why your mileage goes down in winter. To top it off, even when the price was four dollars per gallon, ethanol costs more to produce than gas. You also pay a subsidy to the corn farmers to grow the corn. So every time you fill up you are paying the farmers to produce a non competitive crop and when you pay your income tax you are paying them again with the subsidy.

[larsG35]

Contrary to the post just above this one, that's not what causes bad gas mileage.
It's the Federally mandated use of more ethanol in the gas. Ethanol yields less energy than gasoline hence it takes more fuel to do the same work. That's why your mileage goes down in winter. To top it off, even when the price was four dollars per gallon, ethanol costs more to produce than gas. You also pay a subsidy to the corn farmers to grow the corn. So every time you fill up you are paying the farmers to produce a non competitive crop and when you pay your income tax you are paying them again with the subsidy.

I agree that ethanol (and most other additives) lower total MPG obtained from gasoline. I also agree that the current method of ethanol production for fuel is not sustainable and not economical without subsidy (which shouldn't be sustainable).

I guess I don't know where Starter gets gas, but mine has the same composition (10% ethanol added) year round. Ethanol density changes with temperature similarly to "pure" gasoline.

Ethanol has ~65% the energy density of "pure" gasoline. E10 (the stuff usually at the pump) has 95 or 96% the energy density of "pure" gasoline. So yes, you will lose 1 or 2 MPG straight off, but winter vs summer doesn't change the relative difference. Also, this means don't buy E85 unless it's less than $1.43 right now (based on E10 Nat. avg of $2.03).

[Starter]

Contrary to the post just above this one, that's not what causes bad gas mileage.
It's the Federally mandated use of more ethanol in the gas. Ethanol yields less energy than gasoline hence it takes more fuel to do the same work. That's why your mileage goes down in winter. To top it off, even when the price was four dollars per gallon, ethanol costs more to produce than gas. You also pay a subsidy to the corn farmers to grow the corn. So every time you fill up you are paying the farmers to produce a non competitive crop and when you pay your income tax you are paying them again with the subsidy.

I agree that ethanol (and most other additives) lower total MPG obtained from gasoline. I also agree that the current method of ethanol production for fuel is not sustainable and not economical without subsidy (which shouldn't be sustainable).

I guess I don't know where Starter gets gas, but mine has the same composition (10% ethanol added) year round. Ethanol density changes with temperature similarly to "pure" gasoline.

Ethanol has ~65% the energy density of "pure" gasoline. E10 (the stuff usually at the pump) has 95 or 96% the energy density of "pure" gasoline. So yes, you will lose 1 or 2 MPG straight off, but winter vs summer doesn't change the relative difference. Also, this means don't buy E85 unless it's less than $1.43 right now (based on E10 Nat. avg of $2.03).

It's always possible I'm not up to date on the mix, but my understanding is that the ethanol composition of gas goes up in winter so that it's not the same percentage year round.

[larsG35]

I admit I'm not 100% in the know either. I know there are fuel volitility limits set for certain dates in the year and winter gas is allowed to have a different composition. It was my assumption (perhaps wrongly so) that this increased the ammounts of lighter hydrocarbons. More butane/pentane in winter months, more hexanes/heptanes in summer. Energy density between these are pretty similar.

The EPA limit on ethanol in gas is currently 10% (unless specifically noted to be different) and mine is 10% in the winter and summer. I do know some areas still sell E0 or E5 so it's possible it increases in those areas. Perhaps other additives like MTBE are to blame? I'm pretty curious now; I might have to look into this more.

[Looneybomber]

There are a few stations around here that advertise "10% ethanol" when buying premium fuel, and they tend to be a little cheaper than the surrounding stations for premium. Rarely ever do I see stations advertise they have 10% ethanol mix. I presume they are E0?

[RED_DET]

If you are getting 18-20 city and 25-27 hwy, don't expect anything more....3 years of ownership for a G37, mileage hasn't changed, female driven. My 04 G35 sedan approximately the same mileage.

[Looneybomber]

If you are getting 18-20 city and 25-27 hwy, don't expect anything more....3 years of ownership for a G37, mileage hasn't changed, female driven. My 04 G35 sedan approximately the same mileage.

30 mile cty avg. 12.7mpg. Not on the gas either.
At 80mph it's usually at 20-21mpg. With a strong head wind, doing 50 in a 65, I was getting about 22mpg. This car just sucks gas! I can do about 29-30mpg at 45-48 mph with no wind or slight tail wind.

[RED_DET]

That is horrible. On long trips I run 80 mph with cruise on and average 25 mpg.

[telcoman]

^^^^^^^

You would gain 1 to 2 MPG without cruise control and a full tank of regular 87

Telcoman

[Looneybomber]

That is horrible. On long trips I run 80 mph with cruise on and average 25 mpg.

My 160 mile trip to Wichita, I used cruise for part of it and then let the hills work for me on other parts. 24.5mpg with around a 60-65mph average. I wonder if it's just my car?

[audtatious]

I was getting 25.65 during a mpg test I did a couple years ago in the coupe. 78-80mph w/90% highway. A/C was on and terrain and not flat. That's with all the mods on.

[Checkered Flag]

I drive with a heavy foot, enjoying every minute of the power and torque. Around town my mileage stinks. And I could care less!!

[audtatious]

I don't care around town either but do a lot of highway.

[Fezzik]

You can use uprev and create a lean profile. I have this on mine but hardly ever use it. It will not get you much and you cant be aggressive.

[Looneybomber]

It was 70 degrees today. Filled up in Wichita and drove to Lawrence. Not much for "city" driving; came to a stop maybe 10-12 times. Drove 173 miles, nearly all hwy, and kept the speed between 55-65 for the most part (speed limit 75), depending on how big the hills were. Had a 7-10mph tailwind about 65% of the drive. I did my best to keep the orange MPG bar on the 30 the whole way, which meant NO cruise and constantly modulating the peddle through the Flint Hills.

Parked in my driveway:
29.8 mpg, Avg speed = 54mph. Again, probably 6 of those 174 miles could count as "city" miles and I never had a headwind. Right before getting into Lawrence, I was at 30.1 MPG on the tank. Three stops brought be down to 29.8.

*edit*
My friend just sent me a pic of her Chevy Cruise ECO. She got 45.2mpg on the same drive and smoked me home. Typically she drives 76-78mph in a 75.

[larsG35]

I drive with a heavy foot, enjoying every minute of the power and torque. Around town my mileage stinks. And I could care less!!

I suppose this mostly matches my sentiments. I think it's great that you managed nearly 30 mpg with around 325 hp at the tap.

To be honest, even if that Chevy Cruze got 100 mpg, I'd still take a G35 over it. Just a personal choice at this time in my life; it might be different later. Also bad luck with Chevys.

[Looneybomber]

I think with the warmer temps, the gasoline blend is changing, plus the tail wind helped a lot!

Couple years ago I was on the market for a Cruise eco, but didn't end up buying one due to divorce. While I'd love to get the MPG of the cruise eco, as a single guy, I just couldn't do it. I also couldn't do the Jag XK like I really wanted since I do still have to fit kids in the car.

[telcoman]

There are a few stations around here that advertise "10% ethanol" when buying premium fuel, and they tend to be a little cheaper than the surrounding stations for premium. Rarely ever do I see stations advertise they have 10% ethanol mix. I presume they are E0?

Perhaps its time to end the ethanol rip off?

http://www.nytimes.com/2015/03/10/opini ... ef=opinion

Telcoman