millennm

My stock Rx7 is in good shape. It has 34k miles on it and barely uses any oil. Well it gets around 11.5 mpg around town. Rx7 owners on forums like this one say to just replace your oxygen sensor.



First of all, what happens when an oxygen sensor goes bad? Does it refuse to work in a closed-loop mode and therefore makes the ECU send more fuel to the engine?



I thought the stock oxygen sensors were supposed to last well over 50k miles.



Second, is there any maintenance that should be done to my fuel injectors that would improve the fuel mileage?



Finally, I change my oil every 3000k miles or once a year. I also drive the car year round in New Jersey, including the winter, using 10w-40. Is 10w-40 too thick for the winter? Should I avoid driving the car in the winter to avoid "cold starting" the engine?



Thanks for your time,

Sorry about all the scientific questions,



Keith

millennm

Well Dave Barninger of KDR Performance, http://www.kdrotary.com/, thoroughly answered the above oxygen senser - fuel mileage question.



"Hey Kieth…hope the following helps in some form…the factory o2 is usually a fairly good product and normally last about 70K before getting tired…the most important thing to understand about mazda rx7 closed loop system is that it doesn’t do much at all…you only have closed loop at warm idle..and cruising between 2000-2700 with throttle at a steady 12-18%...you also need to be in fifth gear..as soon as you move the throttle or increase boost pressure it is out of closed loop…now in closed loop on the highway we have had customers average between 22-26 mpg…in town during the winter…forget about it…with colder air temps and longer warmup periods the fuel mileage drops out the bottom…if you are doing short trips with stop and go traffic it hurts it even more…if you are constantly going into boost it lowers fuel mileage again…to really check your mileage fill the car up to the top..get on the highway and cruise for 30-40 miles…stop and refill…then do the math and see what ya really got…hope this helps..holler with any questions…dave@KDR"



Thanks Dave!