Gas Milage Chart 2010 Double Cab V6

the snow [edit: and 4wd] would affect the mileage negatively, however, cold weather is good for the engine. it allows it to run more efficiently since an engine runs as a thermodynamic cycle. i dont remember details or formulas now but could look them up if curious

 

Why did upgrade to a 2012 from a 2010?

Good to see I'm not alone in tracking every fill up.

 

30K mile average was 18.6 mpg.

 

i upgraded to the 2012 for two reasons...

1) i put just over 30k miles on the 2010 in about 14 months. i contacted the dealer out of curiousity to see how much decrease in value i had in that short time. the dealer offered me a trade that i couldn't turn down. i gave him the 2010 and $5900 and he gave me a new 2012 (not bad for a 30k-mile vehicle and a 2 year upgrade imo).

2) i had this transmition issue in the 2010 that annoyed the sh!t out of me. the shift points seemed totally off between about 5-20mph and it would do this hard up-downshifting, engine reving, especially in colder weather, i would slow down around a corner, then hit gas again and the engine would rev to high RPM's, then catch, and take off... it was just really wierd. i posted a couple posts on this forum about it. some said it was normal, some didn't know what was up.

long story short, the $$$ differnce in the trade was a small price to pay, in my opinion, in order to be happy with a truck i plan to drive for the next 15 years... (in addition to the fact that i got an additional 30k miles).

 

and i should add... the 2012 does NOT have the transmition problem that i encountered in the 2010. the '12 drives perfectly... night and day difference. hard to believe it's even the same engine because they drive so differently. i really do think something was wrong with the 2010, but no dealer could find anything wrong with it- just said "that's normal". NO, it's not, i would reply... anyway, i'm happy now. love the 2012.

 

Sounds good, glad you are liking the 2012.

 

Looks like ur averaging bout 18mpg. I'm getting bout 19 but I'm in Houston,Texas and we don't have any snow, ice, hills or long grades here. Also you did not mention what speeds you normally drive at. I drive 70/75 hiway and mostly 30/40 city.
Have u used synthetic fluids in the drive train? Would like to know if you did or do.

 

Cold air is more dense and requires more fuel to maintain the same air-to-fuel ratio. AKA: less efficient, but more powerful.

Fuel also burns more efficiently at higher temps, and your truck will run rich for a few miles until it's up to operating temps.

 

yea the fact that the air is denser makes sense. i don't know how applicable what i'm thinking of is to the real world after all i just remember hearing it. i'll look in my thermo book/notes and see what i find. i was assuming the engine was warmed up to operating temperature though which only takes my truck ~5 miles on a cold morning.

 

so i started looking in my thermo book and remembered what i was thinking of. now i'm going to keep it simple considering i'm just writing with no pictures/diagrams to use.

-all engines are in their basics heat engines. which transfer heat from hot to cold and do work inbetween. (side note: the opposite is called a refrigeration or heat pump cycle)
-the carnot cycle (a heat engine cycle) according the 2nd law of thermodynamics states no cycle can be more efficient than the carnot cycle (i always joked carnot is awesome basically).
-a car engine can be modeled as a carnot power cycle.
-the efficiency (eff) of the carnot power cycle is: eff=1-(Tcold/Thot)

Tcold is outside temp and Thot is engine operating temp/combustion temp (not sure but as long as i'm consistent it doesn't really matter to make my point)

if Tcold= 273 Kelvin (0 Celcius/32 Fahrenheit) and Thot=365 K (91C/197F), then eff=25.2%

if Tcold= 298 Kelvin (25 Celcius/77 Fahrenheit) and Thot=365 K (91C/197F), then eff=18.4%%


A general power cycle eff=Wcyle/Qin which equals 1-Qout/Qin. If Qout is going from the hot cylinder to the cold outside. The colder outside it is, the more heat energy (Q) can escape easier due to heat transfer which always increases with a bigger delta temperature.

an otto cycle best represents and engine but it gets more complicated and its eff. formula doesn't relate well simply with external and internal temperatures so i'll leave it alone.

this somewhat theoretical b/c efficiency is lost in many other places but u get my point.

 

Yes, I too have taken physics and thermodynamics.

The maximum efficiency of a heat engine is simply based off of temperature, sadly it does not take into account the mechanics of the engine or the manner in which the fuel burns. It's a basic guide which can lead you to believe that a cold engine CAN be more efficient. But in the real world, what I stated in my previous post holds true.

 

Yes, colder air is more dense and the ECU will compensate by adding fuel to maintain the proper A/F mixture, but remember this is comparison assumes the same throttle position. It will make more power yes, but think about this. During the summer you have to crack the throttle 20% to go 60mph. During the winter at 20% you will make a bit more power so you would go, say, 62-63mph. In order to maintain speed of 60 you will adjust the throttle to, say, 18%, representing an adjustment on your part. So in the winter both you and the computer adjust to the more dense air, with the computer adding fuel and you taking away. It will still take the same HP to push your truck at 60mph, assuming the same mechanical resistance. Same HP means same fuel usage.

Additionally, dont overlook the benefit of the colder air simply being colder. A colder air charge will allow for more timing because the cooler air-fuel charge is less likely to cause detonation. You can use less fuel if you are less likely to detonate. Additionally, with modern engines, more timing can be added. More timing is more efficient, which means less fuel for the same HP.

These are all part of basic engine tuning (and especially important to understand for forced induction applications).

All that being said, my point is that engines should be more efficient in the winter. However, winter blends with ethanol will really drop your mpg, since as discussed earlier it contains less energy and therefore requires more fuel. This inefficiency greatly outweighs any benefit you get from the colder dense air.

 

That reduction in throttle position for a given power output with colder air drops the manifold pressure. That is a (big) part of your mileage loss in the winter. Remember, the best hypothetical mileage scenario for an otto cycle is to have ambient pressure in the manifold, but of course we could never do that completely. Some (Honda R18, anything Atkinson) do try to come closer. Diesels succeed (no throttle bodies on diesels).

It's the same reason a higher gear gets better mileage, and the auto v6 better than the 6 speed. The throttle is open wider under the same conditions. The energy going down the driveshaft is the same either way but the energy needed to run the entire system is different.

The only time cold is good for efficiency is as discussed before, either ambient manifold pressure situations (full throttle) or the little boost in timing advance.

There's a reason why some eco-modders with speed density systems run tubes from their intake down to the exhaust manifolds or catalytic converters in the winter.

Easy way to think about it, the air going in goes out the exhaust pipe. The end of the exhaust pipe is at atmospheric pressure. In general, the greater the difference in pressure from the back side of the throttle plate to the end of that exhaust pipe, the more energy that is expended to move airflow in that direction.

Of course, once you add cold oils, cold metal clearance...

 

everyone seems to make valid statements.

I hope to take a tech elective on engine design and get to the bottom of this in the near future

 

Iroh, you're right, I forgot about the additional effect of lower pressure in the intake manifold caused by the increase in restriction from the throttle plate! This of course will require more work from the engine and lower the efficiency.

 

I totally missed 81shark's graph... that's a LOT of tanks to keep a record of!!!

 

177 data points to date

 

no, i haven't used synthetics. just went in for my 5000K service and the dealer said he would NOT recommend synthetic. he said there are some engines that will run on synthetics, but it would say on the oil-fill cap. mine didn't say to use synthetic (thanks for asking... i'm gonna research this a little more). i don't know much about engines, etc... (i'm a drop it off at the dealer and do what needs to be done kind of guy). but if there is an advantage to running synthetics, i'm open to it.

 

i'm at 75-80 on the highway (interstate) and probably 30-35 in town.