Around here, diesel is usually 30-40% more expensive than 87 octane gas, so bear that in mind also. If buying a 3.5 EcoBoost 4x4 and leaving the stock tires on it, you can expect about 19-20 average if you run highway about 60-70% of the time. At least that's what mine averaged with the stock Goodyears for the first 40k miles. Some tanks were 20.5-21mpg. I lost about 2mpg going to 34" E-rated all terrains. If going diesel in a new half ton pickup, it's going to have to average around 24-25mpg to break even on the fuel costs versus regular unleaded gasoline.
One thing I didn't know at the time, with the 3.5tt you're not making peak power unless using 93 octane. With 87 you're losing about 20rwhp and 12lb ft compared to 93. Car and Driver did the dyno testing and 0-60 (5.3 vs 5.9 seconds 93 vs 87). And Ford recommends 91 or better for towing or hot conditions. So there goes the cheaper fuel discount.
Loving the F150 Lariat though, just wish it got better mileage. Had I known this before, might have gone with the AT4 despite the inferior interior (and poor dealership experience)
