Hello there,
Went to the dealer to order my new F-150 4x2 Lariat. I wanted to spec the 3.55 limited slip rear end, but the dealer only had 3.73 limited slip on the lot. Went to another dealer, they had the 3.55 limited slip. I drove both trucks and with the cruise control set at 70, the trip meter was reading 14.9mpg on both trucks. (5.4 V8 in both) I am confused, how can the milage be the same on both trucks at the same speed, when there are two different gear ratios. I called FoMoCo's customer service dept. and they did not have a clue...keep talking about the EPA milage ratings..So I decided to post here, and get an answer from the real experts!! Thank you in advance for your help. Rotorman

= reaction to Ford Customer Care

= reaction to dealers...

 

It's only the computer reading you were looking at which is basically a guesstimate.

Did you get a chance to see what rpm's both engines were turning, that's the real guage.

 

Yes I note the RPM on the 3.55 was right at 1975 RPM at 70MPH..but I did not, or can't remember the RPM on the 3.73. I agree that the RPM is the real number, however the fuel flow is quite acurate, at least from prior experiance. Thanks for your input. Rotorman

 

What about tire sizes? Were they the same?