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

I hear you. Let me be specific though, since I travel east to west for work: M-59. If anyone is familiar with the area, they will understand. It's like NASCAR on certain legs.

 

Oh, good. I thought it was just me.

 

True on the hilly terrain vs flat since you can not work the engine so hard on the uphills and just recover the lost speed on the downhills. I will state though that I HATE those who cannot maintain a steady speed, heck I had a dodge car that couldn't maintain + or - 2mph WITH cruise and it drove me insane.

I agree that on a steady drive it should be about the same but I always expect CC to be more smooth then I can be and thus less throttle movement. In the drive for better fuel economy I would also somewhat expect the manufactures to know when in cruise and be less aggressive on throttle response and fueling on tip in. I don't know that to be true but it seems like something that could be done.

 

I live in the Grand Rapids area currently. While it isn't metro Detroit, it certainly also has it's share of traffic like that on 131. But even still I have no problem holding down the right lane at 70 MPH. Let everyone else drive like an asshat and I'll save gas in the meantime. In the summer my truck is known to get 23 and 24 at 70 MPH from time to time although 21-23 is more typical. That's for a 90 mile round-trip commute

 

yeah it's going to drop because of the gearing/RPMs

 

While I thought about that, I really didn't think about that.

 

Surprised there hasn't been a move to reduce speed limits to cut down on CO2 emissions and fuel consumption as was done during the oil embargo back in the 70s. Cheap and effective.

 

Lol I hear ya

 

Drag increases exponentially with speed. Below about 60ish rolling resistance and mechanical friction dominates losses, after 60 drag has it’s way with fuel consumption.

 

that is a really good point. I will be honest, I like EVs, but it’s hypocritical of the government to go about banning gas vehicles over emissions when they won’t, as you say lower speed limits, or even retime traffic lights to make ALL vehicles more efficient.
Dont ask what we can do, not when we can tell you what you have to do

 

The best mpg I've ever seen in my truck with my winter E-rated General Grabber Arctic LTs in 265/75R16 is 11.2L/100km so roughly 20.5mpg. With my summer E-rated Cooper ST MAXX in 255/85R16 drops significantly lower, and the best I will ever see is 13.5-14L/100km so 17mpg. Bear in mind this is long trips at steady speeds, steady rpm in town between 50-70km/hr and only calculated per trip, not over-all.

I'm not sure what perfect conditions people drive in for ever seeing 24+mpg. I've never seen it even with the stock Goodyears and an 8 hour highway trip.

 

my AT has 4.30 gears

 

This image is from an access cab on another thread. I think youll find all your answers here.
https://www.tacomaworld.com/threads/mpg-vs-speed.315165/

 

He is referring to V6 Tacoma's.

 

that's not what he said

 

I get 28 mpg going 5mph. Just drive slow OP.

 

Something to ponder.

My 1GR-FE (4.0L, naturally aspirated) made in '06 averages 19-20 mpg (over 1 year).
My wife's car has a 1.5L Turbo made in '19 it averages 30-32 mpg (over 1 year)

The point to ponder.........
14 years of engine advancement and less than half of the displacement netted an increase of about 10 mpg.

BTW, this isn't to trigger the EV hawkers.


but this will......
1 lb of battery holds less energy than 1 lb of gasoline.

 

Yes: I had seen a few posts from folks in here here about the gas mileage with a V6 when driving at speeds above 70 mph: poor. My truck has the V-6. I did several extended trips to central Maine, New Hampshire and Vermont this summer after seeing these posts and decided to test it out. Long, steady runs with the cruise on and pushing the speed up only occasionally for whatever reason. Keeping my speed between 65-68 as best I could delivered 34 mpg on one of the Maine runs. Later, I went on a round trip of about 100 miles and went along with everyone else at 70-75... sometimes plus. I didn't even have to calculate the MPG: I could tell the MPGs were taking a big dive at those speeds just by looking at the gas gauge and the odometer: mid 20's or less...no question. I confirmed it on the last 50 miles. My truck does better than that on short trips around town if I show restraint on the gas pedal and let the smart transmission adjust itself to "economy mode". I can get 22 avg mpg easily. It's hard though: the six is an awful lot of fun to drive when you put the pedal down, and the trucks' "settling in and hunkering down" sweet spot speed seems to be 75 or thereabouts. It just feels solid there and the complex front suspension seems to wander a lot less at that speed: way less steering-wheel corrections there. YMMV

 

Yes all 4cyl get 4.30 gears.

I was referring to v6 tacos.

 

I saw a red Tesla pulled over today.