frank_a_c

Hoping this is the correct place to post this, I didn't see a separate thread: New owner here, I purchased a '13 RDX AWD (no tech package0) last month with 80k miles on it. The car is in great shape, and the previous owner had all the service records, which were corroborated by carfax as everything seemed to have been done at the Acura dealer. They followed the recommended service schedule.

However, it is coming up short of the estimated MPGs in city driving. By my calculations I am getting around 16.5 mpg in the city with conservative driving. I haven't done a highway trip yet so I would say that is in mostly city driving with about 20% on the freeway. I was hoping to be closer to the 19mpg estimate especially since I've been accelerating slowly, etc. For what its worth, I am running the AC as it is really hot here in CO. I do not know if the VCM has been disabled and don't know how I could find out about that but would be interested to see. It seems like there is some kind of engine "braking" going on around 10-30mph, almost as if the tranmission is kind of shifting downward a bit early. Anyway. Was curious to see if anyone had insights.

PS: for what it is worth to everyone, my previous car was an early 00s Volvo and having just come out of a Volvo forum I can say the differnce is stark. You should see the waterfall of maintenance mysteries on the threads there. Happy to be in something that will presumably have fewer difficult to solve maintenance issues.

altair47

On my RDX, the VCM works in the range of 30-70 miles per hour. It turns on during cruise control or while holding the speed, always turns off during acceleration. Is the engine air filter clean? No misfires? Premium gas?

frank_a_c

Thanks, yep the air filter is brand new, no misfires that I can sense, and am using premium fuel.

Chargersix

We have owned the identical model since we bought it in 2013. 116K miles and we have averaged 23.5 +/- .5 mpg over the lifetime of the vehicle. And we do not drive with a light foot, we like the power of the V6. We also run the air conditioner nearly constantly. Also, we have always run it on regular gas, 87 octane, premium is only recommended, not required. Again, why we like the naturally aspirated V6. Regardless, your mpg is pretty low. Interested to hear what others say.

altair47

I did an experiment, and it turns out that with regular gas you drive less miles per gallon, the cost per mile is the same as with a premium, but you drive more often to the gas station and waste your time.

altair47

Is the car normal to roll in neutral? Parking brake or caliper not jamming? One my customer was driving with the parking brake on.

Chargersix

I was just reporting to the OP my long term results. There was a debate about the merits, or lack thereof, in using premium over regular gas in cars in another sub forum. They may be interested in your experiment there.

altair47

I also read with a scanner in the summer on a hot engine, during the first acceleration, voltage appears on the knock sensor, to this advance the ignition goes from 23-25 degrees to 17-19 degrees. It turns out that driving on regular gasoline in the summer with the RDX software turned out to be harmful for the J35Z2 engine with a compression ratio of 10.5, and you need to reflash the ECU in early ignition so that there is no detonation.I apologize for being literate because I am writing through a translator)

frank_a_c

Good to know, thanks for sharing those numbers. I will keep looking into it. At the moment, its kind of an expensive mystery. to the other posters, I will check that there is no brake drag in neutral. the pbrake is off.

kaehlin

16.5 seems low, but also consider that city driving, idling, etc. will bring the mileage down. Fuelly shows an average of 22.6 for the 2013 RDX. Our 2014 averages around 21, but we've had plenty of tanks in the teens when city driving.

Alex Medeiros

I average 20-23 MPG while driving a lot of city and highway. I tend to rev out my car a lot, so I am very happy with my gas mileage lol. I only use premium too.

egads

I suggest you try & get an Acura dealer if available (or a Honda dealer if not) and have the transmission software updated. The abrupt downshift is one
of the things that addresses.
Otherwise, try to set the tire pressures higher. This can make a big difference in fuel mileage. If someone set the pressures while the tires are hot, they will be too low when cold.
Tire pressures should be with stone cold tires. It is worth having a compressor at home for this. Essential if air is only available miles away.
There is also a learning curve when driving a Honda. Accelerating briskly and backing off, almost coasting can yield better mileage than trying to take it easy.
I think having the VCM in the 2013-2015 engines muzzled is worth any small mileage hit. Especially if you plan to keep it for years.

samiam_68

Take the car on a very level highway, no hills, steady on the accelerator with very light pressure on the pedal, A/C on automatic, pick a day with light or calm wind. At a steady 70 MPH your instant MPG meter in the dash should be reading between low to mid 30's. If it is, that means everything is working fine. If it isn't reaching 30's, that means something is not right. Could be your VCM is not engaging for some reason. That would result in poor mileage in the city and steady light throttle highway cruising.

I have a 2015 AWD, no mods whatsoever, and the car has averaged 23.4 MPG since brand new, with an approximate mix of 50/50 city/highway driving. The lowest individual tank result I ever got was 18.6 in the dead of winter when the car was just a month old. The lowest 5-tank average (more accurate) was 19.8. These numbers are actual calculations - miles driven / gallons to fill, usually about 1 MPG lower than the computer. I live in a NYC metro area suburb to give you an idea what kind of driving I mostly do - lots of traffic congestion, many short trips, and some occasional longer trips. Hot summers and cold winters, winter gas blend from November through April. I use premium gas only - 93 octane.