Hope this is appropriate to post this question here. I bought a used 2014 CX-9 Grand Touring AWD with 3.7l two weeks ago and it's only getting 10 mpg. I haven't been on the freeway much but I'm not heavy on the gas. Air filter is new, oil and coolant are clean and the car idles so smooth I almost can't tell it's running from inside. If injectors were bad I figure it would run rough and I might get an engine light but there is nothing so I'm not ready to take it to a mechanic just yet. It has 65k miles on the odometer and I have a lengthy Car Fax showing many dealer services. Any advice where I should start?

 

Is the odometer showing accurate mileage?
Does it have the original size tires?
Any chance of a gasoline leak? (Big fire hazard if it is in the engine compartment)
Are you using miles driven divided by gallons you put into the tank for your check? Not the drop of the gas gauge.

 

Thanks for the reply PTguy

I'll check GPS next time I'm out.
Yes
No smell, don't see any leaks.
Using miles driven divided by gallons at fill up. I also see matching MPG on the information display while driving.

 

same boat here with a 2016 cx9. Ever get this figured out?

 

Linden, try cleaning the engine internals. For the fuel system use a cleaning product that contains PEA, polyether amine. Two suggested are Gumout® All-In-One® Complete Fuel System Cleaner or Chevron Techron ® Concentrate Plus; follow the label instructions. (Be sure to get the right product...each of these companies has a half-dozen or more similar sounding products.) For the crankcase I've had good results with Auto-Rx which does a great job of gently cleaning the oil-side of the engine, including the piston rings, without solvents. What is the recommended spark plug change interval? And in the end, you might have a mechanic connect their scanner to look for any codes that indicate a poorly performing electronic part that may not yet be bad enough to illuminate the check engine light..

 

Thank you for the tips PTguy, still getting terrible mileage in my Mazda. I recently bought a 2020 diesel truck and it out performs my Mazda by a long way. I need to make time to figure this out because I plan to keep the CX9 for awhile but this is too costly. I'll look at all you suggestions and also follow some suspicions I have. Sometimes I can smell gas when I get out after I shut the car off so I'm thinking about a rich mixture. Also I'm suspicious of the front drive train causing drag. I found some info about servicing and front oil change but I need to make time to look into it more. My wife's 2012 6 cyl Honda Accord has a lot more spunk and get's way better MPG.

 

That would show as sooty tail pipe and sooty spark plugs. If one of the electronic gizmos in this system is failing it should shows on a scan device.
If that's the case it is destroying itself, and you'd likely hear something unusual. Do the oil change here and look for either dark burnt oil or sparkly bits of metal in the oil. But, it's unlikely that this is dragging and hurting oil consumption.