Huge difference, large mpg loss 65 mph to 70 mph. Any idea what may be causing it, my gears?

TXGREEK · October 12, 2019

I wonder if I did get new gears, they’d help ?

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Wiggums · October 12, 2019

Maybe it's the grade.. go to Google Earth, put your mouse on top of where you were and the place you went, Even going up 1,000 ft can be a 15% reduction in fuel economy.

TXGREEK · October 12, 2019

Maybe it's the grade.. go to Google Earth, put your mouse on top of where you were and the place you went, Even going up 1,000 ft can be a 15% reduction in fuel economy.

I’d agree but I’m returning on the same exact road. Only thing I believe it would be is the wind like huntr1117 mentioned

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muddkatt · October 13, 2019

Run the same route again, but this time run 70 in the direction you ran 65 and run 65 in the direction you ran 70.

Edited October 13, 2019 by muddkatt
typonese

TXGREEK · October 13, 2019

Run the same route again, but this time run 70 in the direction you ran 65 and run 65 in the direction you ran 70.

Heading back next week, on the way to Pasadena

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TXGREEK · October 13, 2019

Ok, I believe I’ve figured it out, it’s definitely the wind cause today I was heading beck on the same road and low and behold

This was yesterday coming back

and this is today coming back

ITS THE WIND! It’s got to be, WOW! Yesterday I did notice it was very windy and today not as much, some great ideas though, huntr1117 nailed it!

It’s crazy to think a good strong head wind would affect me so much. I wonder, getting new gears would help? I do typically drive 75-80 outskirts of town. Would new gears help or decrease mpg’s? I don’t want to sacrifice mpg’s for get up and go cause it’s very quick with just 323’s and a tune.

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Snowcamo · October 13, 2019

Ok, I believe I’ve figured it out, it’s definitely the wind cause today I was heading beck on the same road and low and behold

This was yesterday coming back

and this is today coming back

ITS THE WIND! It’s got to be, WOW! Yesterday I did notice it was very windy and today not as much, some great ideas though, huntr1117 nailed it!

It’s crazy to think a good strong head wind would affect me so much. I wonder, getting new gears would help? I do typically drive 75-80 outskirts of town. Would new gears help or decrease mpg’s? I don’t want to sacrifice mpg’s for get up and go cause it’s very quick with just 323’s and a tune.

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I hear you guys are under a " wind advisory on that side of tx" likely your issue.

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dieselfan1 · October 13, 2019

Just leave it and drive it. You can afford the gas .

A few weeks ago I towed my smaller 6x14 enclosed cargo trailer on a 240 mile round trip.

I filled up in Buffalo MN at the Murphy's at Walmart. I got around 10 mpg and used almost the whole tank.

A week later I did the same run same trailer with about 700 more lbs. this time.

I filled up at BP this time and got almost 14 mpg. Same conditions light wind around 70 degrees.

So obviously the gas is the difference in this case and what a difference.

CadillacLuke24 · October 15, 2019

The wind can be insane. I live in Casper, WY, and the wind can get atrocious. Back in October of 16 we had 70 mph gusts out of the SW. WY 220 heads southwest out of town, so I drove that for 50 miles, stopped, and returned. On the way out I got 15.4 MPG, and on the way back I got 36.4 MPG.

KARNUT · October 15, 2019

Even with my Camry, the difference between 72 and 75 MPH is 2-3 mpg depending on added wind.

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flyingfool · October 15, 2019

dont waste your time getting new gears, get another rear diff and swap it in or out until you find the right combo. you'd be surprised after bolting on speed parts that you'll find out the stock set up was best.

People just need to learn to drive slower these days 65mph!!!. when civilians and grandmas can buy a 300hp Toyota Camry, that was the end of calm decent drivers. I miss the old days when hondas only made 90hp , you could blow the doors off of 90% of the drivers on the road. now old ladies leave me in the dust!

Edited October 15, 2019 by flyingfool

swathdiver · October 15, 2019

The gears would make fuel usage more consistent, the truck better able to maintain speed. It would bring your one way averages closer together. Is that really necessary? To each his own.

TXGREEK · October 15, 2019

The gears would make fuel usage more consistent, the truck better able to maintain speed. It would bring your one way averages closer together. Is that really necessary? To each his own.

It’s amazing just how much mpg’s change with a 5 mph difference. I’m not stressing over it and I’m keeping my trucks gears as is.

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BB&Chiveon · October 16, 2019

According to studies backed by the department of energy, the average car will be at its advertised MPG at 55 mph. But as the speed increases:

- 3% less efficient at 60 mph
- 8% less efficient at 65 mph
- 17% less efficient at 70 mph
- 23% less efficient at 75 mph
- 28% less efficient at 80 mph

flyingfool · October 16, 2019

2 hours ago, BB&Chiveon said:

According to studies backed by the department of energy, the average car will be at its advertised MPG at 55 mph. But as the speed increases:

- 3% less efficient at 60 mph
- 8% less efficient at 65 mph
- 17% less efficient at 70 mph
- 23% less efficient at 75 mph
- 28% less efficient at 80 mph

yeah and headwind is not calculated, this is all ground speed. doing 60mph with a 15 mph headwind puts you close to 25% efficiency loss.. holy smokes!

Edited October 16, 2019 by flyingfool