I have nothing to complain about my Mini at mostly 50K and it drives sharp with no problem. It gets older but always been serviced at the dealer from new so I imagine they know what to do.

Since the last 6 months, I noticed my MPG is dropping to about 30 on the freeway from what was in the upper 32. Should I add an additive to clean the injectors?

My driving has also changed. During the week, I drive 5 miles to go to work but on t the weekends about 150 miles on the freeway at about 60MPH.

My feeling is the engine may not have enough time to warm up properly during the week and the injectors getting dirty.

 

*cruising off boost is where the majority of our carbon buildup occurs .. unfortunately for those of us that daily our JCW.. it means the buildup gets bad fairly quickly. You can try the injector cleaner.. it may feel 'sort of' better for a day or two. I run Seafoam through my intake, gas and oil every other oil change, along with a tank of 100oct; oil changes at 3-5k mi.. even then in ~15k mi of city driving with occasional long weekend freeway trip and I can tell my valves need to be cleaned already. MAF readings are down from ~205g/s to ~185g/s now.

typically fuel trim and MPG are effected/controlled by the O2 sensors.. if you continue to see your MPG fall, you may think about replacing the secondary O2.

 

The on board computer is confusing about the data. This morning, I reset before I left for a 120 miles trip through the mountain roads at about 65 MPH. I got 36 MPG. I will do the same test for next week for only in town driving but I can already figure it should drop close to 22-24. This should explain why my average MPG is low.