I know gas loss is a common issue and I have been unable to find an answer. But mine is pretty severe. I'm hoping someone has a fix.

I have a 2009 Odyssey with 130k. We bought it 2+ years ago with 99k on it. Worked great first year. 18/25 mpg. Sept of 2017 it dropped, overnight it seemed to 15/21. I immediately changed the plugs and ran several cleaner through the gas tank. By end of winter it was down to 14/19 mpg.

In Spring I cleaned intake and changed mass air flow sensor.

By end of summer it was down to 13.5 in the city. I changed the downstream O2 sensor (the one closest to the front of the van).

Last month I took it to the dealer. They found no issues. They suggested a fuel system cleanse which I did. They also mentioned back brakes were getting low. The cleanse did not improve gas mileage.

Upon changing rear brakes, found a glide pin was stuck, so I replaced rear calipers as well as the brakes and rotors. Mechanic just gave front brakes clean bill of health at inspection.

Fill up today showed mpg in the city at 12.8.

I'm at my witts end. Can't keep throwing money at parts, can't afford a new van at this time but losing 100 miles each tank of gas is not very economical either. Any help is greatly appreciated.

 

Throwing money away on unneeded parts is never a good thing. particularly when scan-data is available to easily tell you if said parts are needed. FE(fuel economy) directly correlates to fuel trim data. If fuel trim is good, the loss of FE is not because of a sensor or calculation error,but rather it is a mechanical problem.

I suggest taking the vehicle to a competent repair shop(I said competent,which in most cases is NOT the dealer) and have the scan data analyzed for any issues.

If your poor FE is the result of a senor or other electronic issue,it is usually easy to spot in the data. If, on the other hand,the issue is mechanical, those types of problems are typically much harder to pin down.

 

Yeah, the dealer was my third mechanic stop. No one has found an issue. No lights have ever come on. Scanning brings up no codes.

 

Siggghhhh,such is the way of automotive repair nowdays.

Todays vehicles are insanely complex,but the availability of trained technicians are at the lowest levels they have ever been. It can be hard to find a good,competent shop. Try Google or Yelp.


I didn't say to scan for codes. I said to analyze the data-stream. Codes play a very minor role in scan-data, and it is much more important to utilize a full functioning scan tool to diagnose todays vehicles, rather than a simple code reader.....

 

Besides the low mpg, any engine performance issues? Does the engine burn oil excessively? Did you consider compression testing the cylinders?