My 2003 Dodge Grand Caravan MPG has decrease. Could it be the corn the refineries are adding to the gasoline? I have a 3.3 engine. I now have over 113000 miles on this vehicle. I have changed the spark plugs and wires, air filter, gas filter, PCV valve, check trans fluid; check tire pressure. I change the oil & filter every 3000 miles.
What do you think is the problem with my decrease MPG?

 

Ethanol will kill your mileage.

Oxygen Sensor is another good idea.
Since you have 100K miles.
I believe they recommend 80K for its lifespan.
It will continue to work for a long time before it trips a check engine light.

I caught my error code by only doing the following.
Start the engine.
Idle it.
Than race it about 2500 rpms for 5-10 sec's.
Idle it again.
Put on the A/C high and the high beams.
Put the van in each gear:P, R,N,D,1,2.etc.
Return the engine to Park
Turn off the A/C.
Shut it down.
Now run the ignition key diag test..
On, Off, On, Off, On.
Check for error codes.


How bad is your mileage?

 

I thank you very much for the information. I will try your recommendations tomorrow. The highest MPG I have ever reach with this 3.3 engine is 24 MPG on the highway. I would always average city/Hwy
20 to 22 from 2003 to 2008. I am now down to 18.5 MPG average city?Hwy.