Poor mileage on Maxima 2004

[nim]

My Maxima has 69k miles on it, do regular services and oil change with multipoint inspection from Nissan. Everything is perfect as per report but still I am getting 13 mpg in city so re-checked tire pressure, air filter, driving habits but still nothing worked. FYI... I use mid grade gas... please help me on this issue

[maxhopper]

I belive all the Maximas recommend using Premium. If you are using a lower grade of fuel, it's going to cause spark knock, once the knock is detected by the knock sensor, the computer will retard the timing until the knock is no longer present (affecting engine perfromance).

[nim]

I understand... but what about mileage... will it make significant difference in mileage say If I get premium?

[maxhopper]

It should make a difference. How big a difference...only one way to find out.

[nim]

Thanks! I was thinking to go for Fuel Injector cleaning also as 13 mpg is not expected from Maxima with 69k mileage. Initially I added Techron fuel system cleaner to my car`s tank to see if it works...

[sstroudwku]

I will double check the wire diagram tomorrow, however we are having success providing the MAF sensor a secondary ground I've seen gains of 4mpg on the FX50 sport 6-8 on the Max. Our earlier ecm's were experience voltage drop on the ground side for the MAF, it's a 5v ref signal and any drop can hinder this and create a rich environment. Also get some MAF cleaner. Over time deposits build up and can cause the same issue. Make sure it's cleaner specifically designed for mass airflow sensors. Other solvents can destroy the sensor.

Now, I work for Nissan, and I have seen this work. However, this modification is not associated or proven true through Nissan NA. This is just off basic electrical knowledge on how the sensors work and how voltage drop can affect the readings and the interpretation especially on 5v systems.