Transfer Case and front Differential Lubricants for severe cold weather.

I drive a 2nd Gen (2013) Tacoma in Northern Canada and notice a severe drop in fuel mileage during the cold winter months. I suspect it is due to the excess drag on the cold lubricant in the transfer case and differentials. There is a very noticeable rolling resistance when accelerating from a stop. I investigated installing manual locking front hubs to by-pass this problem but found none were available for the Tacoma.
Has anyone else experienced this problem in severe cold weather operations (below -20 degrees)? Is it wise to replace transfer case and differential lubricants with lower viscosity oils to allow the drive system to "roll" with less resistance and thereby not rob fuel mileage?
Your comments are appreciated.
Dean A

 

Your owners manual mentions no difference in gear oil for lower temps. 75W 90 synthetic is pretty slippery anyways.

https://www.toyota.com/owners/resources/warranty-owners-manuals/tacoma/2013

Also, it's just me, but I never worry about fuel mileage-it's a truck-sort of. I worry even less in the winter when you add in winter blends and lots of 4wd use.

 

pretty sure bad mileage in winter is cause of the winter blend or whatever.

my truck drives the same in +20 or -50. machines dont get cold.

 

What oil are you using now? Difficult to find anything commonly available thinner than 75Wxx.

You can also experiment with 0W30 engine oil to see if you get better mileage, but don't use 0W20.

Make sure your tire pressures are appropriate for -20 deg. Low tire pressure will kill your mileage more than any lubricant.

 

Transfer case and Differential lubricant is OEM, Engine oil is 5W30 as spec'd, tire pressures are good.
Most driving is "city" just short runs around town, very little highway. Summer mileage is approx. 300 miles until the gas light comes on, winter it drops to about 160 miles until light comes on! That's about a 45% drop in mileage!! That seems a little too much. If I take it on a highway trip it seems the gear oils warm up enough after 15 or so minutes at highway speed and my mileage improves tremendously! I agree that "winter blend" fuel is not great and have experimented running premium grade fuel but I only see about 15% improvement in mileage. I am curious if this problem is specific to my Tacoma or do others experience the same problem?

 

Damn, 8 years on original factory fill? Must be like molasses in there. Factory fill in 2nd gen isn't synthetic, typically 85W90 or even straight SAE 90. You'll probably notice some gains switching to 75W90 synthetic gear oil.

 

I’ve used bulk synthetic

$29 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 for years all across Alaska and the Yukon. Cheap Walmart Supertech or Chevron Delo 75w-90 gear lube has never let me down in over half a million miles. Your driving habits are going to contribute to your MPGs way more than gear oil viscosities. As stated about the engine, I personally used 0w-30 for easier winter startups.

 

I run 75w90 Amsoil in diffs/transfer case and amsoil 5w30, This winter has not been cold (Edmonton which is the largest most northern city in North America) typically we get stretches -20 to -30C but so far this year maybe 2 days were -20, weather forecast for next week its heading towards -20

 

Run a synthetic

$29 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 and don’t worry about it

 

Not only do we have to deal with winter blend fuel, but engines run richer when cold. I doubt changing your gear oil viscosity will help much. I could be wrong.

FYI, Toyota and GM offer 75w85 synthetic gear oils. You might try that viscosity and see if it helps.

 

Quick question...... is your -20 in Celsius or Fahrenheit?

Either way, the gear oil is likely not the impact on fuel as you assume.

Do you idle after start up to "warm" the truck before driving? If you do, this is a big consumer of your fuel. Suggest to start the truck, scrape the windshield (if needed), buckle up, drive. Go easy on the gogo pedal until you see the Engine Temperature gauge move off "C". Then the truck will be "warm", this will only require 2-3 mile (3-5 km).

In truth, the engine doesn't respond to cold like humans. Yes, the oil will get thicker, but the multi-viscosity oils negate this effect. Yes, the fuel mix will be richer, because the fuel doesn't vaporize easily at cold temps. Once your engine oil is at pressure, you can drive. The engine only needs a few seconds to build oil pressure. When the "genie" lamp goes off, you have oil pressure.

 

Winter gas and letting in warm up in the morning is why your mpg has suffered.

 

I used 75W90 synthetic year round in Alaska. Most of the fuel loss I saw in the winter was from being in 4HI for 6 months , winter gas and warming the truck up so it would actually drive places.

 

Thanks for all your replies. To answer a few questions; -20 celsius, no extended warm ups (start it, clean the windows, and go!), my climate in Northern Ontario is on par with Edmonton. I will definitely change out the gear oil for 75w90 synthetic as this seems to be a common comment and is overdue for my truck with 116,000 km on it.
When the temp drops to -20C and below the first 10 to 15 minutes of driving feels like i'm pulling a trailer with flat tires!! Anything to improve on this is worth a try.
Thanks.

 

Fuel efficiency is always a slippery snake in the winter.

Things to check.
Tires: Correct pressure? Winter tires? Chains?
Drive Train: U-joints lubed or binding? 4WD? Tranny fluid?
Engine: Tuned Up? MAF & Throttle body clean? Spark plugs? Air filter? Serp belt?
Cargo: Hauling any extra weight? Bed full of snow/ice?

Any of these or combinations will impact fuel efficiency.

Initial driving after cold start up its normal for the truck to "feel" stiff.

 

Very well said. It is far more likely to be incremental losses amongst many different things.

The maintenance items you describe are critical for ALL climates - and very much so in climate extremes.