Okay so I keep hearing that Bonnevilles (including the SSEI) is supposed to get over
24mpg. I am only getting about 20-22mpg even when I granny drive it for an entire tank. What gives? I have new spark plugs the wires and coils are fine I do need to change the tranny fluid and the supercharger oil. Woud changing those fluids help my gas mileage any?(I know the tranny fluid would help a little, but enough to get above 24mpg?)

I get 20-22mpg around town here (most of the roads are 45-55mph). I get almost 30mpg on the highway. This seems to be the normal experience.

Day to day ops I get about 25-26. I haven't been able to hit 30, but that'* because when on the highway I drive 70, not 65.

Yea this is in town for about 10 min. everyday and about 40-60 min on the highway at 60-65mph everyday out of the week(accept when I feel a little giddy LOL).

That mileage is about in line with city driving, maybe even a little on the real good side. I get about 24 or so HWY driving, 19 or so average. Lower then that if my evil right foot comes along for the ride.

Check your air filter, make sure it'* not dirty. Check your tire pressure, make sure it'* not to full, not to low.

I run 35 PSI in my tires, seems to be perfect for me.

I get around 20 to 25 mpg...until Dan'* evil right foot possesses mine!

I really hate it when that happens.

Your mileage sounds just fine for the driving you do.

I average 21-23mpg..Didn't reset my average for about 2-3k miles last time and it was right under 22mpg average.

Now if it is just a highway trip and I reset my average mileage I obviously do better.

Easter weekend did a 300 mile trip..all interstate (290 miles of it at least) and I reset my average mileage when I left..

Had the cruise set at 78mph...averaged 29mpg on that trip...havent reset it since then and my average is right down around 23mpg now with all the city driving, spirited driving etc..