fogdoctor

I decided to run three tanks of 93 octane to see if there was any performance difference that I could feel or any improvement in fuel economy that I could measure. 1) I could not feel any performance difference. 2) My fuel economy is worse on 93 (23.0mpg) than on 87 (24.9mpg) after 2 full tanks and I'm on the third, which is at 22.9mpg as well. That's enough of the higher octane stuff for me so I'm just going to run the Sunoco or Wara 87. Same drive, same speeds, mostly cruise control at 60-70mph, and flooring it once a day.

Consultantmom

Thanks for posting. Good to know. I have been wondering about trying 93 octane, but other Acura owners and my salesperson all told me to use 87.

I have read where using Top Tier gas was more important than increasing octane #. I've been using Top Tier 87 so far....getting about 20 mpg around town and a long trip averaged about 25-26 mpg (going 75-80 mph mostly).

Madd Dog

I have gone around this bend many times. I have found no advantage to using 93/91 in my everyday driving. At most, it has been 1-2 mpg, but that is on the highway. It seems that Sunoco works best for me, but again, a minuscule amount.

I never floor the thing, and don’t live in the 3500+ rev range. If you do, then YMMV.

Cuzz

Well, I finally found the source of the low mileage in my RDX... it's me.
Under normal driving (60-70mph) on the highway I easily get 22+ mpg, but with all this COVID-19 madness there's been nobody on the roads so my daily commute is much, much closer to triple digits and my mileage quickly drops to around 16-17mpg. Glad I got that figured out. The lower mileage is much more fun.

Midwestuser1

So pilot driving style choice causes mpg shifts? Who knew

horseshoez

iTrader: (2)

Interesting, my mileage went way up when the COVID-19 thing hit; I made it all of the way from Washington DC to New Hampshire on a single tank of gas; hell, the only time I needed to come off Cruise Control was crossing the George Washington Bridge and then the Cross Bronx expressway. Since I got back from that trip (8 weeks ago to the day), I have yet to use a half tank of gas. Hmmm, guess that means I'm getting about 1-WPG (Weeks Per Gallon).

fogdoctor

Since I’m not allowed to go to work, I’ve been doing a lot of suburbia driving: 20mpg. It’s what I expected.

I drove in Philly last week and that was around 15-16mpg, also about what I expected.

If I were to rate the fuel economy of the 2020 AWD Advance based on my experience: 14-16mpg city and 22-25mpg highway are achievable by most.

DJA123

Assuming Comfort/Sport modes, I'm maybe a bit higher on the city side, but this is still a very realistic range that potential (AWD) buyers should take into consideration.

leomio85

Higher octane fuel shouldn't give any improvement in mileage, unless you're mashing the go-pedal quite often. Even then, I'd think most manufacturers are pulling timing rather than dumping more fuel for lower octane trims. Higher octane prevents knock which allows for more timing, vis a vis, power. That's IT. It's not cleaner. It's not more efficient. It's not some holy water bullshit. It's to generate more power and that's all.

dsc888

I've been averaging 17.5 MPG after about 800 miles on mine with mostly local driving with very light traffic and only about 10% highway miles. I'm a "spirited" driver but keep the car in the default Sport Mode most of the time. I fill up with Regular after one fill up with Premium and have not noticed any differences. I do have an A-Spec so my heavier wheels probably contribute to the lower MPG. But I expected this as the RDX is not light and is a high sitting CUV with poorer aerodynamics than my BMW 340ix.

Speaking of my BMW 340ix, it gets about 21.0 MPG with about 40% highway miles and weights about 150 lbs lighter than the RDX. I do drive it much more aggressively than the RDX but it does have superior aerodynamics as a sedan and it is lowered from factory height by about 1.25 inches with aftermarket springs, which helps even more.

My Honda Odyssey gets about 18 MPG with mixed driving with about 30% highways miles. But is is naturally aspirated and only FWD but does weight over about 300 lbs more than the RDX. And of course, it's driven the most gentle being that its a van.

Overall, I am OK with the RDX's fuel economy. I was hoping for slightly better numbers being that it does have a 10 speed AT but i do know that my driving style and physics does work against it. I don't put many miles on the RDX as it is my 3rd car in our household and we are not going out much due to the pandemic. The only saving grace is that gas is last century cheap and I only fill up once every 4 weeks so the cost of fuel is not a concern at the moment.

ESHBG

How many miles are on the vehicle(s)? These numbers definitely sound realistic but well under the 21 MPG city [AWD] that Acura touts (and yes I know that these numbers aren't always real world comparable but I have found with Honda/Acura products they are usually right in the ballpark).

fogdoctor

I'm getting close to 4k miles. I am happy with my combined mpg but the city fuel economy is quite low in my hands. My combined (when I am not on Philly) on my daily commute + errands is 24-26mpg.

When I have fewer errands and other short trips I have been at 26-27mpg for an entire tank in my AWD Advance.

hans471

I have hit as high as 35 MPG for over 150 mile run with my Advance AWD, but that is not common by any means. I have never gotten "terrible" economy like some say they get but then driving style (as in right foot) has a lot to do that. I drive "normally", not like an old lady nor like a hot rodding kid. After reading the wide range or numbers people were presenting I started paying closer attention and I was surprised at the results: I am actually getting pretty much exactly what Acura posted on the form in the window. Sometimes I drop a little down (playing with the car...its so much fun) and a few times I have gotten higher than rated, but that was under special conditions. All-in-all I can not fault the car as I seem to pretty much duplicate the ratings on the EPA label.

DMV703

How are you still feeling about your RDX now? I just purchased one and I am also shocked at that I’m averaging 18MPG. I used to drive a Honda Accord Coupe V6 and only had to fill up twice a month lol. I have to get used to this because I’m not used to going to the gas station often or blowing money on fuel.

NooYawkuh

Check out post #6 in this thread:

https://acurazine.com/forums/third-g.../#post16712583

I did that ECU reset procedure a couple weeks ago. I noticed an improvement in throttle behavior as I was hoping for. But I also noticed a significant improvement in gas mileage. At least 2 mpg. Except for long trips, I consistently get about 23 mpg in my overall driving. After my last fillup, I switched to the trip display on the MID and I was surprised to discover the previous tankfull came in over 25 mpg. The current tank is running even higher; closer to 26. No change in driving pattern over this time. Just to and from work and local errands.

Worth a try.

DJA123

I may try this for shits and giggles, but I'll be surprised if I see your result. This car will be my last 4-cyl Turbo. For me, it has the negatives of a powerful engine with none of the benefit of a small displacement engine. I don't hate it, I just don't see the point of it. My recent 600 mile trip, on mostly level terrain, with ACC set ≤72, with temps in the 60s, returned 25 out and 22 back. I had an old Honda Element -- which had the aerodynamic profile of a toaster oven -- that returned 27+ in similar situations. I'm not really surprised considering this is a 2-ton vehicle with AWD being pulled around by a 122ci engine. I like the RDX, but the engine choice doesn't suit me.

russianDude

The official numbers for sh-awd aspec:

21 City | 26 Highway | 23 Combined

On long highway rides I am able to get 26 mpg, but its around 20-21 in city.

Agreed, Its not a great fuel economy, but it surprises me that people only start looking at MPG numbers after they buy the car.

Waetherman

I get 28-29 on the highway as long as I'm not pushing 80, and the traffic is flowing. Around the city I haven't really measured but it seems bad.

I'm actually considering a Hondata tune not just for the performance but because someone actually reported better MPGs in regular use - more HP at lower RPM means better MPG, right?

DJA123

As we know, EPA-stated MPG ratings on the window sticker are usually not in sync with real-world driving. Like most people, I didn't expect great gas mileage with the RDX, but it's clearly worse than expected in my case. I also wonder why there are consistent discrepancies between owner reports. Obviously the way we drive impacts mileage, but often we see large differences with highway mileage when cruise control is typically doing the driving. For me to see a 23.5 average over 600 easy highway miles (flat terrain, modest speed, and little AC impact), while others report significantly higher mileage seems odd. One of the common threads I find in this forum is a great variety of owner experiences in many areas. It's very common to see some problem or behavior that is unique to a relatively small group -- more so than other car forums I've followed. The same seems true with gas mileage; with similar variables -- as best as can be determined -- some people just seem to get significantly lower mileage than others.

russianDude

It depends at what speed you drive on highway. The EPA highway numbers are for steady driving around 60 MPH, doing 80+ MPH will lower MPG.
I run 93 octane and was able to get close to EPA sticker on highway with 65 MPH using cruise control

NooYawkuh

I've always gotten slightly better mileage than the EPA sticker on all my cars. I don't have a lead foot but I'm not an egg timer either.

russianDude

When you measure at highway, drive 60 mph with cruise control as much as possible. Also, reset trip computer when you are on highway to take a measurement while on highway, so it does not include driving to highway. I bet most people will get what the sticker says.

JB in AZ

Yes, this is accurate. If one wants to test their car's Highway MPG this is the way to do it.

Routinely driving at 60 mph on the highways (at least here in here in AZ) will cause disruptions to the traffic flow and is probably unsafe. Highway speed limits here are generally 75, and the highways are generally two lanes in each direction. Even big rigs drive over 75 mph most of the time.

sonyfever

The sweet spot in terms of fuel economy for RDX is 40-65mph. You can go up to 70mph without too much hit, above 75+ mpg starts to drop significantly. The trick you can play is to slipstream behind other cars, this moves the mpg closer to 70mph. Stop-n-go, using lower 4 gears all the time kills mpg.

NooYawkuh

I find the sweet spot to be around 65, where you can stay in 10th gear comfortably and still be able to accelerate moderately if you need to. Below 60, you're likely to drop out of 10th if you give it any gas. I've broken 33 mpg over about a 40 mile stretch keeping it in 10th the whole way @65-68 mph. No cruise control. Normally, on the open road, I'm going >70.

hans471

I just completed a ten day road trip from Louisville, KY to the Outer Banks. During the trip I used the "B" odometer to track the total distance for that trip and the over all average MPG. The "A" odometer was set to check each tank of fuel which would better reflect the MPG under the vastly different driving conditions encountered on the trip. I covered nearly 2,000 miles on this trip and the over all average was around 25 MPG. The worst mileage, as expected, was the trip on I-64 through the mountains of West Virginia. Traffic averaged 65-75 MPH including the uphill sections. On the uphill climbs 22-23 MPG was common. Of course the down hill sections were much higher than that. Once at the Outer Banks traffic was on flat roads at sea level and speeds were more in the 50-60 MPH range. Under these conditions 28 MPG (and sometimes even a bit more) were common.

My former 2017 CR-V would average (over all) 28 MPG or so on this same trip (which it did several times). On the flat roads of the Outer Banks it would easily hit 32 MPG. I can live with losing a few MPG between the miserly CR-V and the very spirited driving of the RDX. The RDX performance (and handling) shine in the mountains and its far too easy to let that turbo engine flex its muscle. Of course doing so sucks the gasoline. Its the price of admission to a higher level of performance compared to the CR-V. To be honest my '17 CR-V Touring was no slouch but was not the equal to the RDX.

After two years and thousands of miles of driving across the US, both East and West I have learned that how you drive that RDX is the biggest factor in its fuel economy. If you want to hot dog it though the mountains or around town it will keep "Big Oil" in business. If you can slow down a bit, go easy on the pedal, and drive smoothly you can likely match, or at least come lose, the EPA sticker on the window. Your right foot is the biggest factor. Now some miss the V-6 engine and I can't deny I was a fan. I know many got decent mileage from their V-6's and question why they changed to the inline small displace four cylinders. Acura was not the only company to make that switch. In fact its common. Engineers live through fads too and currently the group think is that boosted small engines are the way to the future, or at least a cost effective solution. I still like a V-6, but I am old fashion in this..

Showkey

Similar to HANS471.......Replaced a 2017 CRV touring 38k miles with ‘21 RDX. Lost about 4-5 MPG in the swap.
CRV would see 28-32 MPG with a the best might see 34 MPG highway under the right conditions.
4000 Miles on the RDX my wife gets 22-23 MPG in mix driving.

Just completed a 1700 mile trip Wisconsin to South Texas avg speed 74-78 MPH avg each tank was 21-24.5 MPG. Thing wind direction was major reason for the fluctuation.

To me, there was no surprise in MPG.

I have 2019 Honda a Ridgeline 36k miles. It gets the about the same MPG as the RDX. That is also no surprise given they similar power.

Baldeagle

This thread concerned me. For the first time, I looked at my computer’s average MPG figure. My FWD RDX just passed 1,000 miles, all mixed driving during the break-in period. My average fuel economy was 27.8 mpg. My previous car was a 2010 Toyota RAV4, AWD V6. It averaged 23-24 mpg in the same environment.

Out of curiosity, I took a short trip today and reset the “B” trip monitor. I live in suburban NJ. Flat roads but many traffic lights. In the 10-mile round trip to my Costco, I hit no fewer than 10 lights and travelled no faster than 50 mph. When accelerating, I kept up with traffic, 2,500 rpm shift points mostly. Once I hit the gas a little harder and it shifted out of second gear at 4,500 rpm. But mostly “light” driving. I averaged 30.5 mpg on that trip.

What the heck is happening? I am not seeing dismal fuel economy. Next week I will travel from NJ to Tennessee and back. I usually travel at 80 mph on the highway. On a recent trip from Florida, I even got a frickin speeding ticket for 82 mph near Rowland, NC. It was a lovely speed trap heading north on 95 just over the SC state border. The police officer was very clear that in NC, speeding more than 10 mph over the posted limit is a felony offense. Anyway, I’ll be sure to check my fuel economy on this upcoming trip and report back. But so far, I’m not hating the fuel economy of my RDX.

Madd Dog

I am averaging a good 5mpg below that which I was getting in my 535.

Showkey

Think if you stay under 50 MPH in flowing traffic 27-30 MPG is very possible and not surprise. Especially with auto stop at the lights.

I am in South TEXAS heat with bumper to bumper traffic on 40mile (20 out 20back witha 5 minute stop in the middle )commute........I am at 17.0 MPG........which also possible and no a huge surprise. Most of mine auto stop is not stopping because of the heat and climate control is not stratified on most of the trip.

Baldeagle

Although I don’t use auto stop, your theory may explain it. Based on my readings, when comparing a V6 and turbo 4 of similar power, under light load (very low boost), the turbo will deliver better fuel economy. Under moderate load the V6 and Turbo are equal. But under heavy load, the turbo delivers worse fuel economy. My understanding is that under boost, cylinder temps spike. To control that rapid increase in temperature, the ECU is programmed to over inject fuel to cool the cylinder. Under boost, a turbo uses a far richer fuel mixture than the stoichiometric ratio would require and in turn destroys fuel economy. Perhaps the next question regards the point at which the Acura 2.0T starts to over inject fuel. If that threshold is very low, that could explain it.

But even at 80 mph, the RDX should require no more than 30 hp to maintain that speed. You’d think that would be considered light load and below any threshold that requires a rich fuel mixture. At 2,300 rpm (about 80 mph), that implies only 68 pound-feet of torque and therefore low boost. It seems very odd to me that a 2.0T Corsair (very similar weight and drag) and even a powerful 535 are significantly more fuel efficient.

JB in AZ

Well, I am just back from a round trip in my '21 Corsair 2.0T from Tucson to Riverside, CA . I mostly drove at 5 over posted speeds, which in CA would be me driving at ~75 mph, and in AZ driving at 80 mph...with occasional bursts of higher speeds to pass, and a few significant grades. With three adults and luggage, AC blasting the whole time, Also, outbound we had a large stretch of stop and go traffic in a construction area in CA..30 minutes of this. I averaged over 31 mpg for the trip (I don't have individual fill up data) Regular gas, My sadly departed RDX would never get that high...period. Looking back through my RDX mpg records for a similar trip (but only two adults) shows three fill-ups at 26.5, 26.7, 28.5.

Madd Dog

Around town, the 535 got 24-25. On the highway, at generally 10 over, I got 29.

I’m lucky to get 20 around town, and often less. I never got more than 24, doing less than 10 over on the hiway.

Baldeagle

31+ mpg is great. Congrats! I just took a 30-mile trip, 100% highway at 75-80 mph. My RDX’s fuel economy was 27.2 mpg, clearly less than the Corsair’s 31+ mpg.

Why the difference? I find it hard to believe that Ford makes a more efficient engine than Honda. The 252 hp 2.0T in the 3,450-pound Accord Touring gets 35 mpg at 75 mph. Granted the Accord has less drag, but enough to explain an 8-mpg difference? Both the RDX and Corsair are very similar in size, weight and shape. What other variable could explain the Corsair’s superior fuel economy? I have a potential theory and welcome any feedback.

I looked a Car and Driver comparison test of the BMW X3 and Mercedes GLC 300. At 75 mph the BMW X3 delivered 31 mpg and the Mercedes GLC 300 delivered 25 mpg. Then I looked at the tires. The X3 uses Pirelli Cinturato P7s and the GLC300 uses Pirelli Scorpion Verdes. According to the Tirerack, the Cinturato P7 is a low-rolling-resistance passenger car tire and the Scorpion is a light truck/SUV tire. My RDX uses Continental CrossContact LX Sport tires, also categorized as a light truck/SUV tire. I believe the OEM tire on the Corsair is the Michelin Primacy Touring A/S, which is considered a passenger tire.

Is it simply coincidence that the two SUVs with passenger tires achieved 30+ mpg at 75 mph and the two SUVs with light-truck tires achieved 25-27 mpg? Could tires make that much of a difference? If the RDX had passenger car tires, would the fuel economy be more like the X3 and Corsair? I'm leaning toward a yes to that question, but its just a theory.

hand-filer

Currently averaging averaging just over 20 mpg city and have exceeded 28 mpg hwy with my Nautilus. Powered by the 2.7 twin turbo 335 HP/ 380 Torque and rolling on Continental CrossContact LX Sport 245/50R20 rubber. The vehicle weighs around 4,300 pounds. I don't think it's the tires.

hans471

1) Extra fuel injected into a cylinder can lower its temperature but it will increase HC emission and can exceed EPA regulated limits. Rick mixtures are not the best way to cool an engine, a good cooling system is.

2) After about 25 MPH the biggest consumer of a vehicles engine power is aerodynamic drag. Weight is only a large factor during acceleration, once at a steady speed on a level road its drag that sucks up the power (and fuel) BUT, drag increases with the square of the speed. This is why fuel mileage drops so quickly with "small" increases in speed. So, the big users of power (fuel) are increasing the acceleration rate and driving fast. I have said many times; the biggest controlling factor on fuel economy in a vehicle is the drivers right foot, how quickly they accelerate and how fast they drive. . Also, the Coefficient of Drag of the vehicle is a large factor. I don't have the numbers handy but I don't believe the body design and ride height of the RDX give it the lowest C of D in its class.

Showkey

1. Your confusing peak cylinder temperature where NOX is created with cooling system temperature. They are NOT using a rich mixture to control NOX.

When comparing Accord and CRV fuel economy to RDX the two things that stick out is weight and four wheel drive system.
RDX is 500-700 pound heavier right out of the box.
Accord the drag has better drag number and 20 HP less.
CRV is lighter and far less power ( night and day difference on the power and drive line).
A quick trip in the ‘19 Ridgeline as a direct comparison the RDX is much quieter on the highway but the Ridgeline gets 24 MPG a with no problem with mud/snow rated tires.
The Ridgeline and RDX are closer in weight. That quiet ride of the RDX is compromise on weight.

Not sure what he other manufacturers are does .........but clearly they are better than the RDX.

I did my return trip from Texas to Wisconsin. I was in the 21 mpg most of the 1700 mile trip. head wind and speed near 80 was a factor. Carrying 1000 pounds of cargo and two place bike rack on the high is also factor.
There is one section where I leave the interstate for 70 miles where two lane speed speeds is close to 60 MPH. Mpg immediately jump to 25 MPG in this slow section.

Baldeagle

​​​First, thanks. Second, your observation lead to a quick internet search.

https://tirereviewsandmore.com/top-1...ficient-tires/

Look at the seventh tire on this list:

“7) Continental CrossContact LX20 with EcoPlus Technology

Here’s our top choice in a fuel efficient tire for pickups, SUV’s and crossovers. The Continental CrossContact LX20 remains true to breed, providing another aesthetically pleasing design done deliberately to invoke better performance from your vehicle. The silane infused tread improves traction and handling, while the grooves increase performance on snow.

The LX20 from Continental not only features an eco-friendly design, but its unique tread compound lowers rolling resistance and enhances fuel efficiency as well. Dry, wet and snow traction is excellent on this model, and the ride is very comfortable and quiet. Treadwear is exceptional for a tire in this class, and is backed with a 70,000 mile warranty.”

So much for my theory. Even if there is a difference between this “top” light-truck tire and a “top” passenger car tire, I doubt it would account for more than 1-2 mpg and the delta between the RDX and an X3/Corsair is about 4-5 mpg. Thanks again.


I agree that a rich fuel mixture increases emissions. But over-injecting fuel is what modern turbo charged engines do under heavy load to cool the cylinders and control knock. That is the primary reason turbo charged engines get worse fuel economy than a larger naturally aspirated engine of equal power when load increases.

And without question driving technique has a massive impact on a car’s fuel economy and aerodynamic drag increases exponentially with speed. I believe the RDX has a drag coefficient of .32 and a frontal surface area around 34 ft². That is pretty standard for a mid-sized SUV and should not work against it. It also implies that the power required to overcome drag at 40 mph is about 4 hp. At 60 mph it is about 13 hp and at 80 mph is about 32 hp. But again, that is no more than other modern SUVs that deliver better fuel economy than the RDX.

Baldeagle

Yesterday, my wife and I took our first road trip in our RDX. Started the trip with 1,281 miles on the new car. Travelled from New Jersey to Tennessee to see family. Took the PA Turnpike West to I81 South. Drove 737 miles in total. Drove 75 mph for the first 400 miles and about 72 mph for the last 337 miles. Maintained even speed up and down all the hills/mountains. Used the A/C for the last two hours when we hit Tennessee. My average fuel economy for the trip was 30.8 mpg. When I hand-calculated the second fill-up (slower average speed), it was 31.55 mpg. My old 2010 V6 AWD RAV4 would average no more than 26 mpg on the same trip. I had concerns about fuel economy, but no complaints from me.

Moving on, I loved driving the RDX! The suspension was firm and well controlled but never harsh. Zero highway float. Minimal body roll in corners. The steering was well weighted, very exact and gave great feedback. Very easy to hold a line. There were a few blasts up to 90+mph and the RDX felt amazingly well composed. The seats were extremely comfortable. So glad I bought it.

tecwerks

Looks good to me, so what's everyone bitching about?