ghbogen

I own Lexus ES 300 2001 with 79000 miles on the odometer, I observed sudden and rapid change in its fuel consumption.In the past the fuel consumption was 20-22 miles/gal and it became 12 miles/gal/The car had a tuneup 2 months ago(600miles). What is the most likely cause responsible for this sudden change?.My friend who is knowledgeable about the cars suggested that it is probably due to the problem with an oxygen sensor.Is it possible to determine which sensor is at fault or one should replace all of them.? I notice that there is a very considerable(100-300%) price difference between sensors manufactured by various companies(Bosch,Denso,Walker,Replacement,Beck/Arney).Could any oxygen sensor described as suitable for my car model be used or is it essential that one uses the OEM parts?. How many sensors are installed in Lexus ES 300?

I own Lexus es 300 2001 which has 42000. miles Just few days ago I noticed that I felt even the slightest bump and the ride became very rough.I checked my tires and the pressure both of which were good.My mechanic checked the car and advised me that he did not see any problemsAny ideas and suggestions?