MPG vs. MPH

2016 TRD-OR DCSB Automatic trans

I travel every week for work. For the last 5-6 weeks I have been driving about 200 miles one-way to a small town in central Arkansas well off the interstate highway system. The signage at the Arkansas state line states: "Speed limits strictly enforced--no tolerance".

I have burned about 9 tanks of fuel while driving mostly 55-65 mph on two lane highways. My fuel economy has averaged in the high 21's and low 22's.

Previously, I drove similar distances for several weeks in succession back and forth to the DFW metroplex, cruising at about 75-80 on Interstate 20. That type of driving consistently gave me fuel economy in the mid to high 18's.

Hard to believe, but slowing down about 15 miles per hour has netted me about 3 miles per gallon, about a 16-17% increase.

 

Welcome to Tacoma. It's an even steeper dropoff in MPG for those of us with a Manual Transmission. It's made me a right lane guy for sure.

 

Makes sense. The faster you go, the harder it is to move through the air.

 

Not at all.

What's hard to believe is you weren't aware of MPG/MPH coorelation previously. From any vehicle.

Depending on gearing and coefficient of drag, the variance will be different of course. But it's always different.

 

65 mph with no change in elevation seems to give the best results. I frequently see 24.5mpg on my trip info when I'm able to make it the entire way to work @65mph with no traffic.

What really kills this truck is change in elevation and long and slight inclines where there's either high load in 6th or it downshifts to to 5th/4th and stays there until after the hill is crested

 

The truck is like a brick traveling through the air.

have you ever driven in slow traffic? When I get into 20-30mph traffic, the truck gets 30mpg average

 

Its a truck

 

I have also previously noted a 1 mpg reduction for every 5 mph above 65mph (i.e. 3mpg for 15mph). It alo works with a headwind....if you have a 5mph headwind, you lose 1mpg.

This is not a Tacoma thing, its simple physics. The power required to overcome wind resistance increases with a cubed function!

 

it's not a cube, it's some exponential function with a varying base

 

Not hard to believe, unfortunately. Heavy ass truck, tiny engine, crap aerodynamics, lots of work required to keep the speed up.

If I remember correctly, EPA fuel economy estimates are done at 45MPH. Anything above that is a coin toss. Useless in the real world of course, but that's what it is.

On my truck I've found that as soon as I exceed 110kph, I may as well start looking for a gas station.

 

I've noticed that on tanks of gas where I'm super easy on the throttle at take off, there isn't much difference than when I accelerate spiritedly.

 

Any time you go over 50-55 mph your fuel efficiency decreases. There is a whole group of people that do what's called hypermileing:

http://www.washingtonpost.com/wp-dyn/content/article/2006/08/03/AR2006080301403.html

I've used some of these principles when driving after reading the above article.

 

I get 19 at a steady 45 mph I get 22 at 55 and can get 23.8 at 60 if I have a 100 miles pretty steady speed but after 60 I start at 20 and go down down there as the speeds increase. I didn't get anything close to this before the Rev 1 update on the automatic.

 

A guy I used to carpool with told me once that the overhead expressway signs that estimated your travel time to a couple of locations were pretty accurate unless he went faster, then it took less time.
No connection to this thread, but I wanted to pass it on.

 

Cruise set at 39 gets about 27

 

Same here. Average speed of travel makes a lot more difference to my fuel economy than acceleration.

 

39mph? Might as well walk and get infinite MPG

 

Distance = rate x time.

Time = distance / rate

Did the public school system in your area fail you?

 

It wasn't me it was the guy I carpooled with and was meant as a humorous story about a clueless guy.

 

This is particularly noticeable in high MPG cars. When I had my 2016 Prius, the MPG difference between cruise set at 55 and cruise set at 65 was 15-20 mpg. Since it's all percentages, I figure that's about the same with the Tacoma.