High speed gas mileage

IH 10 between Houston and San Antonio sees the onset of Texas speed limit denial, which only gets progressively faster WEST of San Antonio. Traffic runs 85-90 in moving parking lots of brain-dead cars riding in the left lane (a bump draft offense back in the old days before airbags when bumpers were still chrome and had rubber protectors), those that ride hard are over 90 pushing 95 and sometimes close to 100 when safe AND clear of traffic. West of San Antonio and Abilene the distances become so great that if you don't run those speeds you can't get there from here.
With this as a backdrop I drove out of these deep East Texas forests and went across Texas to San Antonio this week. I got pretty good gas mileage for pushing the Taco as I did. 85-90 running 87 yielded 18.8mpg. Then I filled up with 91 (or was it 89...I forget) on top of a quarter tank of 87. Speed increased to 90+ the farther west to stay with the traffic and surprisingly gas mileage went up to 19.6! These mpgs included short burst of WOT to drive strategically which should have eroded the averages. Then on the return I put in 87 in a virtually empty tank and got only 17.8mpg as the speeds reduced coming into Houston. Which starts half way to San Antonio now. What is up with that? Better gas mileage at higher speeds? Is it all downhill to SA from Houston or what?

I don't know if the ECM is designed to relearn and reprogram if it sees a significant deviation of driving style, but I am well impressed with how this thing downshifts to fourth and accelerates. Yes, it downshifts way to much, but I like its pep. It seemed to run better the longer I ran it hard. I'm satisfied with my Taco!

 

Nothing is downhill from Houston.

 

Headwind

 

Was there a tail wind/headwind? Makes a huge difference...

 

Now that I think about it, there was a tailwind going. A quartering tailwind, but a tailwind none the less. Might have been a little headwind coming back too, but not much. Logical explanation though.

 

At those speeds, wind direction makes a big difference. Say land speed is 85. Plus minus 7 makes it 78 and 92. Wind resistance at that speed is no longer linear and is approaching exponential.

 

In 2005 I ran my Trans Am at the Big Bend Open Road race. We drove out there, getting a little over 25mpg, averaging ~75 on the highway. On the 118 mile course, averaging 125mph, it got just under 7mpg.

In 2008 we trailered it out there, but with an average speed of 143mph, was in the low 5.x mpg range.

When it comes to fuel economy, speed kills.

 

Unless it’s a diesel, they run better gas mileage at higher speed to a certain extent. 52 MPGs in my TDI @80 all day long down the garden state parkway

 

Shake my head lol.
For a vehicle, anything over around 45 mph will result in declining efficiency due to higher HP requirement. The faster you go the more power is required. No vehicle ever will get better mpg the faster it goes. Even with a strong tailwind you will still get less mpg the faster you go.

This is simple physics.

FYI, our stock trucks take around 57 hp at 70 mph on level ground with no wind.

 

In my casual investigation of gas mileage, the stock 2.7 automatic seems to do its best between 45 and 60 on nearly flat ground. I suppose w/ a scan tool, I could zero in on the best speed for efficiency a lot faster.

 

Not sure why my TDI likes higher RPMs, i get better gas mileage in sport mode reving to 3k, and shifting than the automatic low rpm shifter gets - weird

 

in my 2016 Tacoma, i took a trip to Salt Lake from Irvine, Ca......approx 783 miles.....temp was around 98F......87 octane Shell gas......speed was 68-72mph.......averaged 27.8mpg.......at 65mph it was nearing 29.4mpg.......this trip had hills in San Bernadino, flat desert and steep upgrade from Vegas to St Georges and the plateau to Salt Lake......i love this truck.....it has learned my driving habits and i am some what light-footed......around town and some freeway (75-25) i average 23.7mpg......plenty of get up and go for me.....no jack rabbit starts and constant accelerations......I want to look at the new 2020 but just don't know if I want to go thru all the headaches again of a new truck......however, i would like to have the leather seats.........but i can get Katskins or Classio......i am a happy camper now.......i am approaching 30k.......i can do everything except change brake fluid.....dealer wants $179.......where else can i go and get it done and know its right

 

I wouldn't worry about changing it until it is 8 or 10 years old. Most cars go their whole life on the factory fill of brake fluid.

And nice fuel economy. These trucks respond to a light right foot.

 

There is a '93 4Runner not ten feet from here with 413,000 on the odometer. Original brake fluid. I cannot remember replacing any of the brake components except pads/shoes.

 

WOW......

 

Is the brake fluid still water clear?

 

yes......just a very slight tint of yellow

 

To quote a Klingon, "impressive".

 

You can do everything but bleed the brakes? That's one of the easiest DIY maintenance items there is...does not compute

Any shop can do that for you and for probably half of what the dealer wants for it...nothing special or unique about doing a Tacoma brake bleed. Just take it to any decently rated mechanic.

 

i don't have the pressure bleeder the dealer uses......i can just use pressure on the pedal and monitor the fluid level in the reservoir, but i thought that it requires a pressure vacuum pump.....if all it takes is a bleeding pump and speed blenders I can do that....(did it to my BMW motorcycle with ABS)......but that would require allowing air into the system when putting in the speed bleeders......and i would be hoping to get ALL the air out when I pump pedal and [ump in new fluid.......thats why I said except brakes.....but I'll check around for a good shop and see what they use and what they charge........thanks for the reply

edit: does that also bleed the ABS module