2011 MDX with poor gas mileage
 

Hi all - I have a 2011 MDX which has always gotten anywhere from 18-20 mpg. The past few months, however, that has been decreasing and I'm to the point that I'm only getting about 12-14 mpg. I've had it into the dealership twice. The first time (about 6 months ago) my oil light was also coming on. They replaced the O2 sensor and said that should help with the mileage. It did not. I had it back today and everything checks out mechanically. While I have only used premium (91 or 93) gasoline, they suggested that I switch to a "top tier" provider. I'm not sure why - the places I have gone for gas (usually Costco or wawa) have not changed at all in the 8 years I've had the car.

Anyone had this issue? I've searched the forum and it seems like they have ruled out the "usual" suspects (sensors, spark plugs, fuel injector, filters, fuel line, etc).

Thanks!

If regular stuff has been check then check the not so regular stuff: Tires, Brakes, Oils, etc..
-Old Tires can Increase their rolling resistance with time.
-Caliper pins can get stuck and increase friction in the brake pads.
-SH-AWD oil and Transfer fluid can be old enough to cause extra drivetrain loss..
-Check engine compression, etc. etc. etc.

Isn't it the other way round?
Old tires become hard and lose grip resulting in lower rolling resistance.

As the tire ages it also loses OD so the metal weave in the tire gets closer and closer to the ground which allows it to heat up as it rolls.. When the tire is not moving sure its super hard but as it rolls it becomes too hot so the tire becomes extra soft.
The lost traction is due to lower thread pattern.

Hmm I have observed a drop in mileage after getting new tires in both my 2008 Accord V6 and the MDX.

Again this is on east coast where summer is short

Agreed, I've always experienced fuel economy improve as tires age.

Monitor your oil level closely.

If oil is getting past the piston's oil control-ring, it will end up in the exhaust.
It will be detected before the (dirty) exhaust gets to the catalytic converter, by the upstream O2 sensor.
The CPU will increase the fuel to each injector to compensate (for the "rich" burn).
Sending more fuel to each injector results in about 20% lower MPG.

Eventually, the upstream O2 sensor will need to be replaced and if you continue to burn oil, your catalytic converter will need to be replaced.
Back in the 50s and 60s, when engines started burning oil you could just continue to pollute the environment and nobody cared, but now you'll fail an emissions test.

I also have 2011 MDX with only 23,500 miles on it and I get 14-16 MPG on premium 93 octane gas from Kwik Fill-United Oil gas. It used to get about 18-21 MPG when it was new (2,000 miles)and before the dealer re-programmed the six speed auto-Trans per an Acura recall for lubrication issues with those transmissions.

The gas mileage is awful and I've discussed it with Acura service, but there doesn't seem to be a fix. I like the MDX very much and will probably hang on to it for awhile.

Costco gas is rated Top Tier.

Also as tires wear, their diameter gets slightly smaller. With each revolution you're covering less distance compared to a brand new set. But the ecu reads the wheel speed at the hub so it only counts axle revolutions, and cannot factor in for tire wear (or different size tires). It does not know the exact miles traveled (because that depends on the tire diameter), so it's always slightly off. With smaller tires it's going to think you traveled more miles than you actually did. That's why MPG increases after tires are 50% worn compared to new ones.