In the past 8 months or so I've notice my indicated fuel economy decrease by 20% or so. There hasn't been anything new or usual about the car such as warning lights or anything. I do hear the slightest of clicks when I turn the wheel full lock to the right. This leads me to believe the front driver's side axle is on its way out. So I've scheduled a service at a local, well-rated indy to perform the following services: driver and passenger side axle replacement, front diff (transaxle) fluid change, and rear diff fluid change.

I don't typically like this approach to solving a problem but there isn't anything else glaringly wrong. Also the diff fluids have never been changed and I'm approaching 78k miles on the car.

If this maintenance doesn't improve the mileage my next move would be to change the spark plugs. Has anyone else had this happen on their car? Thanks


Pic for clicks

 

^
Just curious, is your well-rated indy guy going with low cost aftermarket drive axles or higher end OEM's below?

 

I am not sure. They are next to a Carquest so I imagine their parts are from there. I'll call them.

 

DonPatrizio - If the transmission and differential fluid haven't been changed in 78k miles, are you keeping up with other maintenance like air, oil & filter change? Have you owned the vehicle since new? I have 142k miles on my 2017 RDX and still average 23+ mpg (based on the computer). I'm not an automotive expert but replacing the axles seems overkill for the "slightest of click" I would have your mechanic check the suspension first before replacing anything. Reading through these forums, I haven't seen any issues with the axles.

I would start with the basic maintenance things first. Maybe disconnect the battery so the transmission re-learns your driving (this worked for me; i bought my RDX used). If he does change the transmission fluid, have him stick to HOnda fluid. These transmissions can be touchy.

Good luck.

 

I am extremely skeptical that differential fluid changes will have any effect on gas mileage. That said both are past-due with that mileage anyways so good idea to get them done.

If you've ever changed your own oil, you can do these too - they are just as easy, and you'll save a considerable amount of $$$ with a DIY job vs having the shop do it.

 

I got the car with 20k miles and change the oil every 6k at the dealer (full synthetic coupon). I did the trans fluid change around 30k miles and had it reflashed because it is a fairly clunky transmission. Thankfully I've not had any problems there (yet), but the fluid change and reflash haven't affected the shifting.

I called the shop to ask them to see what's wrong, if anything, once they have it on the lift before throwing parts at it.

DIY is somewhat out for me now that I'm in my mid 30s w/ bad back. To be in my teens again...

 

If you think your 30's are bad, ait until your 50's........lol

That sounds like better strategy. I use the "maintenance minder" for reminders about maintenance but it sounds like you are doing everything. The problem with loss mpg is there are many things that could be wrong. If you had a "check engine" light, it would be much easier. I had a dragging caliper on a 2015 Camry. It didn't come to light until I had a service performed at the dealer and the service manager mentioned needed rear brakes. I remembered that my pad thickness was twice as thick the last service. He confimed it from the last service and had them check the calipers. After dealing with two Syracuse NY winters (aka Salt City), I needed my rear calipers cleaned and lubed. And this was affecting my mpg. I just blamed it on the hilly roads.

Good luck.

 

I picked my car up today and they couldn't duplicate the clicking axle so no change. They did the two diffs and the oil change. Price was $330 for everything so very reasonable. They did forget to put the anti squeal fluid on the back of the pads (which is what I asked them to do. I guess it was lost in translation because the tech said 'we checked your pads and they're fine.' 'Yeah they're brand new...I just needed the anti squeal goop on them.' 'Oh.') so I'll have to make another appointment with them next week.

I may just have to live with the loss of MPG. I'll do the spark plug service probably some time in November. It won't likely help but it's still maintenance.

 

I took a road trip up to Howe Caverns and Cooperstown, NY this weekend then headed south to Bethel NY to visit the Woodstock monument. On the long downhill sweepers I had the car in S5 and cruise set at 50mph. Under normal circumstances the descent and engine braking alone would hold the car at a steady speed, but I could feel the engine applying throttle to counter abnormal drag which caused a surging-like effect. So, something is definitely causing additional drag and it might not be mechanical. Now I want to schedule an alignment even though it tracks straight.

 

I would check if the calipers are dragging a bit. Sounds like you live in the northern tier where you get true winter weather and use salt on the roads. Two winters in Syracuse did it to my Camry.

Good luck

 

I agree, it's probably dragging brakes. On a slight downhill, put the car in neutral, and see if it starts rolling down easily on its own. If it doesn't, then it's likely brake related.

 

@DonPatrizio I know you said DIY is out, but if you have a floor jack and jack stands or even the OEM jack to change a flat tire, you can test each corner of your RDX. Simply jack up a corner of your vehicle and spin the wheel. Does it spin freely? How quickly does it slow down? Do you hear any rubbing or grinding? You will need be careful checking the front axle wheels as you will need put the car in neutral and use the emergency brake on the rear axle to spin the front wheels. Just a thought to be able to check for dragging brakes.

 

Just a suggestion to check for any possible brake related problems. Get yourself an infrared thermometer and after a drive just check the rotor temperature for each wheel, if there's any problem you'll see a distinct difference in the rotor temperatures, front temps should be similar with each other and higher than the rear rotor temps, rear temps should be similar with each other. I've used the infrared thermometer whenever I do a brake job just to see if the rotor temperatures all look balanced and reasonable. A very useful tool to check brakes, AC diagnosis, coolant flow and temp checks and other checks. Doesn't have to be expensive either.

 

Update: It was the tires. I bit the bullet and ordered the OEM Michelin Primacy MXM4s after debating for months about the car. I did a deep dive into size profiles, weight, rolling resistance, and way too much reading for simply a set of tires. What I found was the MXM4s are one of the lightest tires for the car which is what contributes to the way it drives from the factory. The Michelin website lists them at 27lbs, and the second lightest is the CrossClimate2s at 29lbs. The Sumitomos I had on the car are ~32lbs and the first set of replacement tires I had, Vredestein HiTracs, were about the same. Long story short, this review sealed the deal for me to get the MXM4s:


In summary, in trying to save a few bucks on non-Michelins, I ended up where I should have been all along. The car drives so much better with these tires.