Today I drove my truck to the dealership for the A/C seat TSB to be done. They gave me a 2015 Lariat, and I wasn't half a mile out of the dealership when I started wondering what engine it had since it didn't accelerate quite like mine. As it turned out, it was a 3.5L EB but with 3.31 gears as opposed to my 3.55 gears. Other than that, both are Supercrews, 4wd, etc. Mine has 6,400 miles and the Lariat has 5,600 miles. And, mine has more options, like the sun roof, A/C'd & vibrating seats, etc so should be slightly heavier.

Here are some differences I noted of the Lariat from mine:

• It seemed to accelerate less rapidly off the line when driven the same way as mine.
• It was slower to go into 6th, or maybe I should say it went into 6th later and at a higher speed.
• It needed to downshift more than mine when accelerating lightly, but didn't do it quickly so the truck frequently seemed to be in the wrong gear
• It seemed quieter. Dunno if it was the tires or the engine, but it just seemed quieter.
• It ran faster than mine. Or, maybe I should say if I didn't watch it closely I'd be running almost 5 MPH faster than I thought I was.
• It rode better than mine. Not sure if it was the smaller wheels on the Lariat or the higher tire pressures I'm running (although my ride didn't change much when I upped the pressures), but it handled bumps better.

The bottom line is that I'm surprised how much difference the gearing seemed to make.

And now for another surprise - MPG. The Lariat was sitting at an average of 19.1 MPG on Trip 1 650 miles when I picked it up, and I was impressed with that as who knows how it had been driven to that point. So, I took it easy on it and never used the cruise to maximize its mileage. And I got it up to 19.5 MPG on the LoM by the end of my time with it. Pretty good I thought, much better than mine which has been turning in hand-calculated 17.5 MPG (18.1 on the LoM) pretty consistently, but I had always used cruise.

Now for mine. I'd filled it up with 91 octane gas this morning and had aired up the tires to 38/42 yesterday. So, on a lark I didn't put it on cruise at all today, but drove it exactly as I did the Lariat. At the end of the round-trip of 72.7 miles the LoM is sitting on 20.0.

No, I'm not saying my truck really got better MPG than the Lariat as the latter had a number of miles on its tank that was holding its average MPG down. And, the LoM's aren't that accurate anyway. But, what I am saying is that my truck did better today than it has ever done, and yet it was driven on the same roads it has been for many other tanks. But there were three differences:

1. 91 octane ethanol-blended gas instead of 87 octane pure gas
2. Tire pressure of 38/42 instead of 33/33
3. Driving with the throttle instead of cruise

Anyone want to hazard a guess as to which one of them is mainly responsible?

 

On Fords that Ive owned, the higher gears do better on fuel economy. Thats why on my next Ford Im am getting 3.31s... I drive with a light foot and I hypermile. Ive gotten 16-17 with my 6.2..... but I plan to daily drive my next Ford.

 

I noticed a similar difference between my 2012 ecoboost max tow and my 2015 max tow, 2012 had 3.73 and the 2015 has 3.55. The 12 felt a little quicker and was in sixth gear at about 40 mph, felt like it towed a little better also, the 15 is in sixth at about 45 and sometimes seems reluctant to drop a gear when the go peddle is pressed a little to lightly, to the point that you know the engine is being lugged. The upside is that the fuel economy is about 2 to 3 mpg better doing the same kind of driving, I was not on fuelly before and I don't know how accurate the old trucks fuel economy lie-o-meter was, the current truck is reading about 5 or 6% higher than hand calculated. With regards to the 2012, tha trans would shift wierdly at times, like it was confused, the new trucks trans has not skipped a beat, very consistent operation compared to the old truck, and the old truck was not bad.

 

When the CC is used, the PCM will do what ever it takes to maintain your desired speed no matter the terrain. CC doesn't have the ability to hypermile or anticipate ascending a hill or descending one. Basically, I never use my CC unless my foot is just tired. The traffic is typically too heavy anyway.

 

Yes, higher/taller gears are better for MPG, but aren't as good for towing. As in everything, there's a trade off. I just didn't expect to be able to feel the difference as easily as I did.

But, no one commented on the big jump in MPG on my truck - unless Tim is attributing the majority of it to cruise control? I'd like to find it is due to fuel as I'm lazy and like to use cruise. But, I'm seriously doubting it has much to do with fuel, so guess I'll try doing without cruise a bunch more to see.

Yes, cruise cannot anticipate. And I learned how to drive in order to achieve max economy long before the term "hypermiling" came into existence. I loved to read the write ups on the Mobilgas Economy Runs, and they frequently would relate the driver's tips. Dad had a '54 Plymouth and Mom and I took it on a road trip and had a competition for MPG. I won.

This upcoming trip pulling the boat is an excellent time to forego cruise. The first 120 miles or so will be on Oklahoma's very first turnpike, and it is full of steep hills. Cruise would power up and probably downshift going down. I'll let the speed drop maybe 5 MPH going up, as long as I'm not creating a hazard, and roll to whatever going down. Should prove interesting.

 

Are you sure that the truck you had as a loaner really had 3.15 gears? I did not think that a 4x4 F150 could have anything taller than 3.31s...

 

Good question. The window sticker was in the glove box, but the bit that gave the axle ratio was torn off. So I went to the owner's manual and in the towing section found that the 3.5 EB came in 3.15, 3.55, and 3.73. But, I forgot to see if it was 4x4. So, I've now looked and you are right - nothing higher/taller than 3.31 for a 4x4.

Thanks for the correction. I'll change my original post. But, that means the difference between 3.31's and 3.55's is easily noticed. Significant even. I can't imagine what 3.15's would feel like. My truck felt like it was in Tow/Haul mode in comparison.

 

These are excellent points to consider. Now I'm even more confused. I currently have 3.73's and was certain I wanted the 3.31 in my next truck. You now have me thinking I might be better off with the 3.55. I like the way my truck responds but mpg suffers. To further complicate things I know the final overdrive ratio will be different on the 10 speed compared to mine. More to consider now.

 

Don't miss that I was wrong about what gears the Lariat had. Since it is a 4x4 it must have been 3.31's. If I were you I'd drive trucks with the different gearing you are considering as I think there's a big difference. I'm not saying one is better than the other since how you use it and what feels "right" to you will be different than to me. But the gearing makes a much bigger difference than I expected.

 

Very interesting, Gary.

I test drove trucks with 3.31 and 3.55 and don't recall that much of a difference, but of course I didn't put more than a few miles on each. I remember the EB truck with 3.31s wanted to spin the tires up the on-ramp in second gear, which really impressed me. My current truck with 3.55s doesn't do that, but I suspect the PCM limits power to avoid that, which is just fine with me. Rubber is expensive!

I wouldn't mind better fuel economy in exchange for more shifting around, but so far my truck has kept me happy with its fuel economy. It's a good 1-2 MPG better than my Max Tow '13 would get with 3.73s, so I can live with that. I'd be very interested in a more long-term MPG report with the same driver under the same conditions, but of course that's tough to do.

 

OK, appreciate the clarification. In my test drives I perceived less of a difference between the 3.31 and 3.55 gears in the Ecoboosts than in the 5.0L. I attribute this to the flatter torque curve with the turbo-charged engines. Since the 5.0 needs to rev to make power, the difference between gear sets is more noticeable in the normally-aspirated engine.

My 5.0 with 3.31s is wonderful on the highway, and less so around town. If I had to buy again, I might go with the 3.55s as a compromise, but might even seek out the 3.73s and sacrifice a few MPGs overall. That said, the 5.0 with 3.31s is a rocketship compared to the 5.4L Triton 2-valve in my '03 Expedition.

 

I was really surprised at how much difference there was, and still can't believe that it is only the delta between 3.31 and 3.55. But, doing the math that is a 7% change in torque to the rear wheels for the same throttle setting, and that's pretty significant. I assumed it was the non-EB six, but then spotted the boost gauge, so then guessed it was the 2.7L. Nope.

But, how much "learning" does the computer do of driving style? Might someone have been driving the Lariat around that never asked it to downshift? It seemed reluctant to do that, so was frequently slow to respond to my gently requests.

 

My 3.5L EB is very reluctant to downshift. I find it doing 1100 RPM climbing the mountain; especially if I have to let off the throttle. If I try to give it a little gas, it sounds as if it's lugging until all of a sudden, the boost comes on, _AND_ it downshifts, and we're off to the races! The missus asks me "Why did you do that?!?!" To which I respond, "I have no clue."

If I put the tranny in tow mode, then the same scenario starts at 1500 RPM, and neither the downshift, nor the sudden boost come on, and I accelerate gently through the climbing curve.

 

Interesting. That's kinda what I was finding with the Lariat yesterday. Nothing, nothing, and then I got both the downshift and boost. And you have 3.31's?

 

I've never owned a 3.73 geared truck so I have no comparative comments on that note. My truck feels like a rocket to me, is there really a faster ecoboost F-150 stock? That would be amazing! If I bought my truck for towing or for work, I'd go for the 3.73's and grumble about the MPG's but, I'd have a machine built for the task.

One thing I found kind of funny was back when Ford was using the 6.4L diesel, I was comparing trucks on the lot one day. IIRC, the 3.31 truck that I looked at had the same GCWR as the 3.73 geared truck. I attributed that to the enormous power of the diesel. Maybe I'm wrong or mistaken but I wasn't high or drunk.

Gary, you mentioned that the Lariat that you drove as a loaner had smaller tires than your rig. That says a lot. My truck came from the factory with OE 235-70-17 and I upgraded last year to the 265-70-17 and I lost about 1 MPG. I also went from a bologna skin tire to a more aggressive all Terrain tire. The ecoboost engine is just that fussy.

Hope this helps.