2014 Nissan Titan Mileage, 5.6L V8 (don't laugh too hard!)

[MetroMPG]

Originally Posted by ghengis86

Re temp; why is that and why so dramatic? Cold tranny fluid and increased driveline resistance? Too much engine cooling and reduced combustion efficiency? I thought that winter gas blends had less energy per liter than summer too.

/curious

All of the above...

- increased time spent below normal operating temp (= fuel enrichment)
- auto transmissions hold lower gears longer while in warm-up mode
- increased fluid viscosity (engine, transmission, bearing grease)
- increased tire rolling resistance, even at the same PSI
- increased electrical loads (heater blower, lights, defrosters, seat heaters, wipers)
- slightly increased aero drag from higher air density
- and of course driving in more wet/slush/snow

[JRMichler]

I wish I knew exactly why the temperature has such a dramatic effect on my MPG. I do know that the air is about 30% more dense on a cold winter day compared to a hot summer day in Northern Wisconsin. When the air is 30% more dense, air drag increases 30%. Engine power also increases proportional to air density, and fuel consumption increased with engine power.

I have experimented with low viscosity and synthetic lubricants, and never saw a significant change. Now, I just put in whatever oil the manufacturer recommends.

I do know that my truck's rolling resistance increases a lot in cold weather. I suspect that much of that increase is from seal drag. Modern vehicles have many seals keeping oil and grease in, and dirt out. They all have friction. My hypothesis is that the seals shrink in cold weather, increasing drag. Someday I intend to borrow a thermal camera and look into it.

[MetroMPG]

Originally Posted by JRMichler

I do know that the air is about 30% more dense on a cold winter day compared to a hot summer day in Northern Wisconsin.

30%! What temperature range? http://en.wikipedia.org/wiki/Density_of_air

[user removed]

From the freezing to boiling point of water, atmospheric density drops by 25%.

Atmospheric density drops by 50% at 18k feet.

regards
mech

[JRMichler]

From ASHRAE Psychrometric Chart #1: At 100 deg F and 80 deg F dew point, the air density is 14.7 cubic feet per pound. I've seen hotter, but not by much.

From ASHRAE Psychrometric Chart #2: At -30 deg F, the air density is 10.8 cubic feet per pound regardless of humidity. That's about the coldest we normally see, but there was the day that I drove to work at -46 deg F.

14.7 / 10.8 = 36% difference.

[Eastwood]

Hey ghengis. You're not alone! And yeah, that little turbo diesel ram gets great mileage! I know some guys who have it.

I'm currently in North Dakota (only one more week and I get back to my Cruze!!!!) driving a 2011 Dodge Ram 1500 4x4 with a 5.7L V8 Hemi. It has a leveling kit on it so it sits up a bit. Necessary for the job.

I do a lot of highway driving up here and when I'm not fighting constant headwinds of 40 mph for 8 days straight, I can get tank averages in the 18 - 24 mpg range driving 60. I am lucky because it does drop down to 4 cylinders when cruising, even has a little "ECO" that comes on on the dash display lol.

I've been driving this truck for almost 4 months now and have had plenty of time to experiment. 60 seems to be the sweet spot on it. Either that or 45. 50 - 60 is okay, but cruising at 45 and 60 are the best spots for my truck.

You can check out my Fuelly log for my truck:

Christopher (Ram 1500) | Fuelly

The weather and wind up here do not help at all, but sticking to 60 has really helped. And I also run the highest octane I can get my hands on, which is sometimes only 89, but I usually try to put 91 in it. I have not seen any 93 up here near the Canadian border.

My advice would be up your tire pressure to what you're comfortable with (I keep mine around 50) and take your time to try out a tank where you don't go above 60 or 65.

[MetroMPG]

Originally Posted by JRMichler

14.7 / 10.8 = 36% difference.

Thanks for clarifying -- I wasn't sure if you were describing a *typical* difference, or the extremes.

[CAPTAIN CHAOS]

Originally Posted by MetroMPG

Thanks for clarifying -- I wasn't sure if you were describing a *typical* difference, or the extremes.

Sounds pretty extreme to me.

We have similar extremes around here but typically winter morning lows (Jan/Feb) will be single digits (deg F) and summer highs will be low 90's. A 50deg swing in a period of 1-2days is not uncommon either.

Man, I'm getting depressed just talking about this.
My mileage is already down 1-2mpg (3-5%) from the stinkin' cold and wind. Last winter had me down to 36mpg's at times (from 40-41).

[kafer65]

Chaos, you and me both are suffering greatly on climate induced mpg declination! What about, since engines are air pumps (in essence) and the higher density has to be compensated for with fuel to maintain its A/F ratio and timing its shooting forin its maps. Hows that for an explaination for the eco-interuptus?

[ghengis86]

Bad tank; 15.8. Lots of city driving and super cold temps! Ugh, that was a bad one. Oh well.

Thanks for all that info. Wish I had the cylinder deactivation of the Ram; or the turbo diesel!
Nissan is definitely behind the big three for fuel economy tech. But the lower sticker price makes up for it for a few years.

I did notice though this week that I couldn't get the transmission to drop into top gear at the usually 45mph in the mornings, which would usually be ~1,000rpm. Definitely held gears longer. It does have a transmission temp gauge, which I noticed was solidly in the "C".

I will say, when you need to merge or change lanes and have to step on it, this engine is pretty peppy! I try not to use the boost button often, but its fun!