Is it normal for MPG to greatly decrease after 70+ mph

If I drive 60-70 mph, I get 18-19 mpg. But when I drive over 70 mph, I get 15 mpg. Is that normal?

Truck is totally stock. I was expecting 20-23 at highway speeds but I never get near that. I use cruise control.

 

Yes
Over 2000 rpm is no bueno

 

Aerodynamics come into play big time over 55-60mph in trucks/suvs. The faster you drive a truck (basically a brick moving through the air) the harder it is and more work the engine is going to have to do. This is even more true with a lifted truck since it has more surface area so keep that in mind. Gotta pay to play

 

Wind resistance is exponential. As you go faster the resistance keeps getting higher at a higher and higher rate.

More resistance = less mpg.

 

Where are you that highway speeds are over 70?

They exist, just not in a lot of places

 

Any interstate around here people are usually rolling at 75-80mph regardless of the posted speed limit.

I drive 80mi a day mostly interstate and average 18-19mpg with varied speeds of 70-75mph.

Edit- OP, try not using cruise, I’ve found I get far worse mpg with it on.

 

In a word, yes. Higher RPM's, more wind resistance, etc play in. That's exactly why I stick to 70.

 

Plenty of the Southwest has 70+ speed limits. We've got 70 and 75mph speed limits within 10 minutes of Reno on 2 different freeways for instance and quite a few in Cali and AZ too.
As soon as we hit Utah on I80 it bumps all the way up to 80mph. Gets sketchy when towing a rig on a car trailer with most trailer tires rated at 75mph or less and semi trucks are blowing by in the left lane at 85+ mph.

 

U don't do over the speed limit in a 65?

 

Most of the interstates in OK outside the urban areas are 75 posted. People roll at 80 to 85 routinely. And yes the mpg sucks on these trucks 65+.

 

We recently moved to Montana and practically the whole interstate system is 80. Although I can go that fast if really needed, for all intents and purposes I literally cannot do the speed limit. Seems like a huge mistake to have all this truck and be prevented from doing one of a vehicles most basic tasks.

 

There are lots of threads about mpg on these trucks. For a stock Tacoma the mpg you are getting is not normal imo. Have you made modifications? Lift or more aggressive tires?

 

If I did over 20% of my driving at interstate speeds I would drive something else.

 

Cubed...

 

Yep, higher speeds take more fuel, Nascar and Truckers know this well.

 

Auto or manual? I have the 6 speed and best I got was 20mpg doing about 65-70 the full tank.

Edit: I have a 2nd gen, just realize this was for the 3rd...

 

The sweet spot on my Lexus ES350 is about 70 at 29 mpg. At 80 it drops to about 28mpg so ok....

 

Mostly West Texas, Interstate 10 has some parts with a speed limit of 80 MPH.

 

Out west. Montana for one.

 

Over 80 with the AC and 3,500 rpm will kill MPG