I just got back from a big trip. Ouch! I was average 15 MPG on the highway cruising at 80. Is this right? I feel like my Disco did better.

 

Hard to judge driving habits. Assuming you used premium and did you best to not pass people or accelerate much, that seems a little low. I can get 18mpg highway no problem and if I try really hard, getting over 20 is possible even in hilly terrain. My best average was 22 on a four hour trip but 20 is normal for me. I have a MAF that is a year or so old, new plugs, new O2s etc.

 

I was running 87. I wasn't being aggressive, but I was going 80.

 

The fuel was probably the issue then, combined with a steady 80. I usually drive 72-75. Always best to run the recommended fuel. Unless you have the V6? I know the V8 requires premium, not sure on the other engine.

 

I think 80mph is too much to expect max MPG from these bricks
Next road trip, try 70mph on premium gas

If it's still low, maybe something else needs attention

 

Assuming V8, 15 is low, but 80mph in a brick is a lot of resistance. I just did a round trip of pure highway and averaged 20.2 at between 70-75 (and a motorcycle on the hitch hauler on the back). I only run premium.

 

Get 20 out of the 07 regular gas running 70.

The key I have found is not crossing the 2000 rpm threshold while cruising, I can get 16 out of the kitted out 06 on 33" tires doing that.