Sixto,
I sometimes feel sorry for these people that can only say "impossible","your lying", "can't be", etc. In how many cases does it happen that if they has said "I don't understand how that can be, could you tell me more?" If they would they may learn something from others that have spent a lifetime learning things. I have been working on cars for about 50 years now, and I believe I have learned at least something. My 500SEL has gotten 28.9 average mileage going from NC to Flordia. This was 99.9% hiway, cruse set at 80 most of the time, with extensive tuning for MPG only. It had a very poor idle, and little low speed power. It ran like gang busters above about 50. 0 to 60 was probably 15 sec which is terrible for a 500SEL. I sense have tuned it back for overall drivablity and it is a joy to drive. Same trip to Fl after seting it back to (Normal) got 22.1 which is still good in my opion.
If people would just listen to others and ask how, they may learn something useful.
When I was 16 my Father was probably the dumbest man I knew. When I was 50 he knew more than i will ever know. When he passed away, he was the smartest man ever. Actually, he was always the smartest man ever and over those many years one thing he taught me was "listen, you may learn something" and he was right as usual.
Now if there is anyone that would like to know how to get 29+ MPG from a 500SEL or probably most any car, let me know and maybe I will give away some of the knowledge I have gained over the years. But if you say "Stop lying" or something to that effect, forget it.

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84 500 SEL (307,xxx miles)