Winter fuel mileage...I have concerns !

[MustardTiger]

What's people getting for fuel economy in the cold/winter? Below is my average for a 6 hour drive. No head winds, no cargo, just me in the truck, and the only potentially effecting mod is 285/70r17 SL tires.

-Temperature -21c (about -6f)
-110km/h (~68mph) cruising speed, flat prairie
-15.8L/100km (~14.8 mpg US)...it actually landed at 16.1L/100 when I got home
-Maximum safe driving range...only 350km (~218 miles) !!
-Fuel used is 87, top tier

My old 2nd gen 5.7 Tundra got the same gas mileage in conditions like this, and that was a real truck with a real motor!!

I realize fuel economy drops in the winter...wasn't born yesterday. But like I said above...this is v8 half-ton territory...possibly worse

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[Kjc]

It has alot to do with the tires... My mileage is worse than last year when I had the stock tires... Now running 285 70 17 also and avg 14 mpg.... Temps have been between 0°-20°f....so I'm usually warming up the truck for at least 10 mins.... Mostly short trips 10-20mi at a time

 

[scythanith]

I am the same or worse, 15-20l/100 km in the winter. Still on factory rubber.

 

[Will721]

I was actually pointing out the issue in the main fuel economy thread. It's all down to the software, and more specifically, how the ecu is controlling the transmission to maintain temperatures. It seems even with shutters these trucks struggle to maintain temperatures in the cold. The ecu has very aggressive controls to try and maintain those temperatures too. The truck hangs at higher rpm in low gears until set points in coolant, engine oil temp, and trans temp are reached. Even when switched to "manual mode" you cannot force a shift into higher gears unless those temps are maintained. Torque converter lock up seems all but impossible to achieve below 20*F. Another observation is that at very low temperatures the trucks will actually start cooling back down as if the thermostats are bypassing too much coolant.

It's almost as if the cooling systems work too well, but funnily enough the trans still had a tendency to overheat in the summer months. What I'd really like to know is how the guys with aftermarket trans coolers are doing in the winter months. A direct comparison to a stock truck would be nice.

 

[MT-Taco]

My gen 2 tundra 5.7 was about 10-12 mpg in below 0F temps, LT305/70r17’s My Tacoma is 15-17 below 0F mpg, SL285/70r17’s.

 

[MustardTiger]

@Will721 good points. And given that the T24A in hybrid variant achieves up to 41% thermal efficiency...engine cooling efficiency is quite a balancing act, especially in extreme cold operating conditions from what I can see. In addition to that, with burning extra fuel in cold operating conditions, combined with low tension piston rings...this is a recipe for oil dilution, which I'm experiencing. After my 6 hour drive today, my dipstick is now 1/2 inch above the full mark!! I'm estimating that additional 1/2 inch is about 300ml...which equates to 5% dilution. So with 0w20 oil..and that amount of gas in the oil, it shears way below the 20 weight viscosity grade.

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