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Discussion Starter #1
I have mentioned this a few times. People say after 60mph or so MPG drop significantly.

I have noted at 75 mph I am not in boost if cruising on flat ground. When slight hills using cruise control, you can hear the turbos spooling but I still am only seeing a few pounds of boost, still in 6th.

@ 75 MPH I am about 2100 rpm, no boost flat ground. This is factory 4.10s and 32 inch tall tires with cruise control on. Those of you with other gear ratios, are you in boost in this same situation?

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I have mentioned this a few times. People say after 60mph or so MPG drop significantly.

I have noted at 75 mph I am not in boost if cruising on flat ground. When slight hills using cruise control, you can hear the turbos spooling but I still am only seeing a few pounds of boost, still in 6th.

@ 75 MPH I am about 2100 rpm, no boost flat ground. This is factory 4.10s and 32 inch tall tires with cruise control on. Those of you with other gear ratios, are you in boost in this same situation?

View attachment 163894
You have factory 4:10’s? Wow that is a unicorn in itself.


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Wow, that thing must tow like a beast!

I'm on the opposite side the gears world, 3.31. I can't say what my boost is, no gauge. I can say once it gets above 65 the mpg drops like a rock. 65 on flat ground is easily mid 20s, 70 is low 20s, 75 is high teens. With a smaller trailer this drops exponentially.

What are you getting for mpg at those speeds?
 

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When I'm at 75, flat ground, I'm just shy of 2000 rpms and 1/2 a pound or so of boost. 3.55 2.7

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It's not that you will cruise in boosted form at lower RPM's but the changes in load put you in and out of boost much more frequently with larger variations around 1600 RPM's . I have 3.73 gears, 6 speed, a 2.7, turning 31.5 inch tall tires. I get better mileage cruising at 2000 than 1600 and a more consistent vacuum reading. Recently did a 500 mile trip with a custom street 93 octane tune averaging 25.5 MPG. At less than 60 MPH I will lock out the top gear(s) as needed to stay above 2000RPM, boost only comes on when I use more throtle including 70 MPH in 6th. KM
 

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I thought only tremor's got 4.10's? At any rate when i dropped from my usual cruise speed of 120kmh to 100ish i got another L per 100k so 11.9 instead of high 12's which is just under 20 mpg. Its a 18 2.7 with 3.73's. I'm guessing that with my altitude thats as good as she gets
 

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Woo does have a tremor which is why he has the 4.10's . Sorry I have nothing else to add to this


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I always see “boost” but only because of elevation. Even just cruising at 55 i am seeing ~1lb or so. This is with 3.73’s.
 

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I'll add that my mileage does drop like a rock after 70. I struggle to maintain 20 mpg at 75. It seems a mpg or two worse after my new tires, which are the same size as stock but heavier, and with a more aggressive tread.

I've also made several other changes to the truck that may slightly affect mileage, such as 2.5 inch lift in the front and 1.5 in the rear, and removal of the front air dam. It's impossible to say what pieces of the puzzle have caused the change, but I'd suspect all of it with an emphasis on the tire weight/tread. It has never done all that well at 75-80 though.

We recently took a trip to Myrtle Beach and left late both going and coming, so I spent a lot of time driving 75-80 where I could. I wound up at almost 21 round trip, but there were periods of slower driving through towns and whatnot.

I've had trips before where I stayed under 70 and netted solid mid 20s.

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Discussion Starter #10
Basically, what I am wondering, is the gearing causing lose of fuel mileage due to being in boost to maintain 75mph. With a 3.31 for example, it is more load and less mechanical advantage, are you boosting to maintain the MPH causing the fuel drink?

That being said, rpm can factor in here too. With 4.10, it will be higher rpm, although 2100 is not that bad considering. With me, I am running n/a here, which really helps mpg.

This is considering everyone here has stock wheels and tires. Heavier wheels and tires and taller tires can change these factors.

4.10s are also optional on raptors I believe.
 

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I'm almost certain that's true. I've seen that hold water in the super duty world.

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I've kicked the idea of regearing my truck to 3:73 to match the towing power of the 2.7 3:73 trucks, and Jason at stage 3 recommended I just jump straight to 4:10. Seems to think I wouldn't lose a lot of mileage, and might even do a tick better in town. Especially if I ever want to go up in a tire size at all.

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Basically, what I am wondering, is the gearing causing lose of fuel mileage due to being in boost to maintain 75mph. With a 3.31 for example, it is more load and less mechanical advantage, are you boosting to maintain the MPH causing the fuel drink?

That being said, rpm can factor in here too. With 4.10, it will be higher rpm, although 2100 is not that bad considering. With me, I am running n/a here, which really helps mpg.

This is considering everyone here has stock wheels and tires. Heavier wheels and tires and taller tires can change these factors.

4.10s are also optional on raptors I believe.
But you are almost never NA. Even when you are cruising and seeing vacuum to the manifold, its probably still less vacuum then it would be without the turbos. Or the throttle body of the NA engine would be wider open to provide the same load.

I have a very hard time believing that even a little boost somehow causes the mileage to exponentially drop vs a motor that was running purely NA. In that condition the wastegates are barely operating, the turbos are basically just freewheeling and providing a tad bit more air then the engine would naturally consume, hense the small boost. Its eliminating pumping losses by feeding air to the cylinder by using exhaust heat that is produced whether you have turbos or not. In that condition the turbines should be providing almost zero back pressure.

Where the Ecoboosts **** the bed is when you go to high boost and are drawing a huge amount of power. Then the engine needs to run rich to maintain EGT's and what not.

I do believe that the higher numerical gears are beneficial in some cases. Someone towing a lot or someone who is constantly climbing and decending hills might see a benefit.
 

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Basically, what I am wondering, is the gearing causing lose of fuel mileage due to being in boost to maintain 75mph. With a 3.31 for example, it is more load and less mechanical advantage, are you boosting to maintain the MPH causing the fuel drink?

That being said, rpm can factor in here too. With 4.10, it will be higher rpm, although 2100 is not that bad considering. With me, I am running n/a here, which really helps mpg.

This is considering everyone here has stock wheels and tires. Heavier wheels and tires and taller tires can change these factors.

4.10s are also optional on raptors I believe.
Actually 4:10s are the only ratio on Gen 2 Raptors.

My '13 XLT SCrew with 3:55s gets 22+ at around 55 to 60. Bump to 65 and it gets 20 to 21, at 75 usually 19.5 to 20. Over 75 is goes down significantly. Don't remember the exact RPMs but I know at 75 it's definitely in the 2000 range.

Headed out on a trip on my '19 Raptor tomorrow and will see how it does on the highway. Have only done a couple of short trips so far and it's getting close to 20 at 60 mph.
 
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