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Acura RDX Real World MPG

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  • c_hunterc_hunter Posts: 4,487
    Oops, in my quest to be a smartie-pants I messed up my numbers (noticed on the way home). The RDX engine spins at 2400rpm at 70 mph, which is about 300rpm lower than my last 4-cyl car. It runs around 2050rpm at 60mph. In 5th gear, it spins 35rpm per every mph, not the 27 I quoted.
  • oncrankoncrank Posts: 8
    We're looking for ways to improve the mileage for people who obviously aren't as adept at driving for mileage. You know how the car works and clearly are able to use that to your advantage to get decent mpg, others aren't so lucky. That's why we're here nitpicking ideas.

    Yes, a 6 speed is often used just for shifting performance. It COULD be used to provide a better gear ratio for cruising on the highway while not sacrificing smooth performance in the other gears. While it is already low, it could be lower.

    Acura 4.533 and 0.612 X3 Man. 3.73 and 0.85 X3 Auto 4.44 and 0.67

    The BMW does come standard with 17's as opposed to Acura's 18's, but has an option for them. Now I get confused with how this works out in terms of best gear ratio for low rpm highway cruise. If I figure this right, the X3 has a smaller tire which doesn't help gearing yet it still gets 26mpg. This would effectively be the gearing if I understand the numbers correctly doin most of the work for mpg. If you compare the RDX's with the Auto gearing as the manual doesn't really apply here, the numbers are close but there is still room. If a sixth gear was put in that dropped it a hair above/below(not sure which way the #'s need to go) what the bmw's is, that would probably make for a pretty good cruisin suv mileage wise. Trimmin some body weight to boot, and you have something very sweet for both worlds.

    Lemme know if I'm way off on this cuz I always had trouble understanding gearing principles.
  • sb55sb55 On an Island in VermontPosts: 184
    Larger RIM diameters do not mean that the tire is larger in daimater. Usually the 18" option will be a lower aspect ratio to make the diameter the same as the 17".

    2007 Miata, 2010 BMW 535xiT, 2014 Chevy Silverado LT Ext. cab, 2006 Subaru Legacy Wagon

  • c_hunterc_hunter Posts: 4,487
    The gearing gets complicated, but there's a good explanation here:

    http://en.wikipedia.org/wiki/Gear_ratio

    Their equations at the end are somewhat misleading because they don't note a lot of unit conversion is needed to make it work. Here's the equation I follow:

    V = C*RPM / (Gt*Gd*1056)

    V = vehicle speed in mph
    C = tire rolling circumference in inches
    RPM = engine RPM
    Gt = gear ratio of a particular gear in transmission
    Gd = gear ratio of differential

    You can estimate the rolling circumference as:

    C = 2 * Pi * (D/2 + W*AR/25.4)

    D = rim diameter in inches (ie, 18)
    W = tire width in mm (ie, 235)
    AR = tire aspect ratio (ie, 0.55)

    To get an accurate circumference you really need to measure one full revolution of the tire on the ground, but I think the estimation (which uses a nominal tire size) is OK for comparison.

    I am sure the BMW 17" and 18" options have the same (or nearly the same) outer diameter (and hence circumference) so there is not likely a gearing difference there. You can compare the BMW and RDX nominal tire sizes with the equations to get a real comparison of the overall gearing.

    The only thing I can say relative to gas mileage is that I tend to drive with a light foot on the throttle, rarely mashing it. Even when traveling at 70-75mph on the highway, I am pretty easy on the throttle. That gives me 25mpg on trips, or 21-23mpg in mixed driving. I am sure I would be in the teens with more city driving.

    When considering the RDX, I was alarmed by low MPG reports and paid attention to the trip meter during test drives. What I found was numbers of 14-16mpg when driving on city streets around the dealership with a reset trip meter. That climbed into the upper 20s on the highway, and settled out around 22-23mpg over a 12 mile test drive. If I only looked at the 14-16 aspect, I would have been turned off.

    I also repeated the same test loop with my old car, also with a reset trip meter, and noticed very similar trends. It too got MPG in the mid teens in the city and then climbed into the 20s on the highway. That car never made it higher than the low to mid 20s and settled out around 20mpg.

    I think I mentioned earlier that my previous car was very similar to the RDX in power and also had a turbo 4. But it weighed about 350 lbs less. Considering that, I think the RDX is doing pretty good if it returns similar or slightly better MPG under the same driving conditions.
  • oncrankoncrank Posts: 8
    For sb55, if I remember correctly, both companies sites list the same exact tire except for the rim size. I might be wrong, but I checked it yesterday, acura site to seems to be spazzing on me right now. I'm not comparing BMW's sport package as they do use a different tire to make up for the size difference in rims.

    Thanks for the link hunter, thats good info. Yea, I think alot of people just dont feather the throttle enough on the highway. I live in a hilly area so I might have more of a hard time getting decent mileage combined everyday. Part of the reason why I'm so adamant about suggestions for improvements. I'll be in the market for a new car within the year and I REEEEEEALLY like this suv, but some improvement in mpg aside from some minor interior improvements would be great and really put me over the edge in getting it. Right now, I'm still on the fence.
  • c_hunterc_hunter Posts: 4,487
    I don't know if this helps any, but I took my RDX on a lot of ski trips this past winter, and it got great gas mileage even with mountain driving thrown into the mix. These trips had about 180 miles of highway driving (with a few long hills) and then about 60 miles of backroad mountain driving (crossig about 4 major mountain ranges). I was still seeing 21-22mpg for these trips. The mpg did drop into the 18-19mpg range when I filled up in the mountains with a reset trip meter, and then climbed into the low 20s once I hit the flat lands.

    I would say that you should worry about MPG if you did a lot of city driving , or all city driving. If you do highway driving or back road driving, the RDX should be OK. At 45-55mph on country roads, the MPG soars into the mid 20s -- that seems to be the sweet spot..

    I was really on the fence about the RDX, in fact if you look at some of my posts from last fall, I was not too thrilled with the RDX. But it gradually grew on me; I love the interior and handling, and I felt better about the MPG after many test drives. Finally, the drop in street price to invoice or lower (I paid $30300 for my base RDX) sealed the deal. After 5 months of ownership and about 6800 miles, I am real pleased with the RDX. It's a very comfortable ride for my commute and on the many ski trips I take.
  • oncrankoncrank Posts: 8
    See, those are responses I like to see. My daily commute is about 50-50 highway/city. The city part in the morning is about 50-60mph with minimal lights til I hit the highway which is 75-80mph the rest of the way. Coming back, almost the same highway, maybe 10-15mph less. City, turns to alot of stop and go cuz of more traffic. Good to know it does get into that sweet spot around that speed.

    This has nothing to do with our discussion, but I agree with some of the complaints listed in the shorter reviews. For $30,000, your passenger seat should move for you. My wife and I ride together alot so it would see alot of use. All other base Acura's have bluetooth standard on them. I was told by the dealership I test drove at that first year outs dont get that. Huh?! If you want a car to sell, you hit it out of the ballpark the first time. You dont nitpick stupid crap like that.

    Anyway, back to the topic. Well, it does seem if you pay attention to what you're doing and adjust your driving habits a little bit, you can do well with this suv. For the sake of people that have a little trouble changing, an extra gear and a little less weight would go a looooong way in making this suv the exception and not the rule.

    Thanks for your inputs c_hunter, really appreciated the responses.
  • stathisstathis Posts: 32
    I have realized that as the real MPG improves in my RDX, so does the accuracy of the reported MPG.

    I gradually have seen the accuracy of the reported MPG improving. (I kept detailed records at fill-ups). The 1st month the onboard computer overstated MPG by 4.8%, the second month by 4.1%, and by the 4th month by only 3.4%.

    My overall MPG is now around 18. This is all good news.
    In my tests I have reached up to 25 mpg in freeway driving at 65 mph at 2000 rpm, with no AC, no load, and without invoking the turbo like when passing other cars. I guess it's the downtown traffic that brings down my average.
  • mtairyordgemtairyordge Posts: 144
    Another Wife/MPG report.

    After 2500 miles of mostly driving in country settings with LOTS of rolling hills and average mpg of 22.7

    We are traveling from Md to NMB South Carolina in a few weeks and I am looking forward to see how it does once we get past Wash DC traffic.
    Problem is we are leaving at 2pm and should be lucky enough to hit rush hour. Oh the joy. Maybe the real time traffic will help.
  • mjo1mjo1 Posts: 16
    For anyone interested..........I'm just about at 1200 miles on my RDX base package. So far I've been averaging @ 23 mpg - a combination of city and highway driving. On long highway trips I've been getting @ 26 mpg. My "city" driving involves a 2 mile roundtrip to work and an occasional trip to the store. The onboard computer MPG is pretty accurate, as it matches up with my own calculations.

    I don't do alot of stop and go driving, no quick accelerations, and I haven't used the paddle shifters.
  • Do you normally leave you AC on? Curious if those numbers are mostly with AC on or off.

    Rich
  • johnny98johnny98 Posts: 88
    I just got back from a 3000 mile road trip through the Rocky Mountains and Pacific Northwest. Terrain was varied (up and down mountains, winding coastal roads, 80mph freeways, etc.), but very little city driving. I averaged 24mpg for the whole trip. A couple of times, I got 27mpg (average for a full tank). I never got less than 21mpg (for a full tank).

    People that are getting 15mpg must be doing lots of cold starts and stop-and-go driving. No gasoline engine is efficient in those situations (though maybe electric might be). I think the RDX's MPG is great (for a 2 ton vehicle) on the open road.
  • newdriver2newdriver2 Posts: 68
    Does anyone live in Manhatton, NY and have the actual MPG want to share? Or any people only use the RDX for city use only and have the actual MPG. I travel a lot in NY City and want to know the MPG before buying it, thanks.
  • baldeglbaldegl Posts: 16
    If Downtown Chicago (Water Tower Place) works, we average about 20.5 in mixed driving.
  • I just bought my RDX three months ago, I only do city driving in downtown Chicago. I was more than disapointed to learn my average MPG is 10.4. However, this has been during some of the worst continuously hot weather we have seen in years, so the AC is always on. I would not say that I drive crazy fast, just trying to keep up with traffic. Other than the low MPG, i love the car, much better than my 03 discovery
  • carlitos92carlitos92 Posts: 458
    WOW. You either need to take that thing in for service immediately, or find a new way of calculating MPG. Even Hummer owners who race off-road would balk at 10.4. :surprise:
  • 10.4 is the lowest I've heard... must be computer error or you are doing wrong maths.
  • After drive my 08 RDX w/tech for one week with 143miles (delivery with 4 miles). just refill the full tank with 9.11 gal

    143/9.11 = 15.7mpg (Trip Computer Show 15.8mpg)

    Location, 95% local drive 5% highway in the Bay area CA.

    I drive it very easy and slow since it's still breaking in..... but 15.7 doesn't sounds good. what do you think ?
  • I bought my RDX a month ago and already got 3K miles on it (sounds like a greyhound).

    80% highway and 20% city in varied terrain of pacific northwest. I think 20mpg is probably the average depends on the driving habit. I don't hammer the gas and use cruise control on highway. And open window/roof instead of AC in local.
  • Just returned from a 3 day trip from Irvine, CA to Paso Robles, CA and back. Got 20.8 mpg overall which was about 80% highway/interstate. About 10% was on narrow, hilly roads connecting the various vineyards in Paso. At home I'm getting 17+ mpg in suburban driving. The car is only about 3 weeks old and had about 500 mi at the start of the trip. My only complaint so far is that the tires generate considerable cabin noise, especially on concrete highways. The noise seems to interfere with the voice recognition system.
  • rickpoolerickpoole Posts: 27
    We've had an RDX three times when one of our cars was in the shop. We were surprised the mileage was so low the first time we had one so the next time we did an experiment. We filled it up, reset the mileage and drove it conservatively like we do our TLs. Then we filled it up again and drove it fairly aggressively. Then we filled it up again and drove it on the highway. Each drive was at least 20 miles, which was plenty of time to get a stabilized reading. Our results (as displayed by the computer) were 19 mpg city driving very conservatively (almost never letting the turbo kick in), 15 mpg driving aggressively, and a very surprising 23 mpg highway at only 65 mph. Actual computed mileage (miles / gallons) was slightly lower, 5-10%. When we reported this to the dealer they said the reason was "we always put regular in our loaners, you'll get much better mileage with premium". Then we told them we specifically got a loaner that was near empty and filled it up with premium so we could see what the best mileage the RDX could deliver. We definitely could tell a difference in performance and mileage compared to the prior loaners so the premium did make a difference. With gas up over 50% and continuing to rise since we did these tests the RDX is out of the running now for replacing our 1999 TL due to unacceptable mileage.
  • mtairyordgemtairyordge Posts: 144
    Additional Wife /MPG report. She now has 11700 miles on her 2007 RDX recently switched to regular, about 500 miles ago. Mileage at 23 mpg, computed by hand. I do the calculations myself as I fill it up. I wish I could get that kind of mileage.
  • I'm getting very poor results on the RDX. With conservative driving (minimal turbo kicking in) I'm getting about 14.8mpg. With more aggressive driving and turbo kicking in more often its 10.8-11.4 mpg. This is a 4 cylinder car, not a hummer or escalade! Every time I look at the gas gauge I cant believe how quickly it goes. I only do city driving, so it is all stop & go, and short trips. But I never got above 15mpg. :mad:
  • johnny98johnny98 Posts: 88
    15mpg with minimal use of the turbo is really terrible. Is this on the highway or on stop-and-go city streets? I regularly get 24mpg or more on long distance highway trips. Half-city and half-highway is around 20mpg. If you're getting much less than 20mph on the highway, I would get the car checked out. Obviously, you're going to get much lower gas mileage at slow speeds with lots of cold starts.
  • ubercheapubercheap Posts: 9
    Driving an '07 RDX with about 8K miles. Trip through NY, PA, MD with a lot of highway but with a fair amount small speed-trap towns and 2-lane roads and hills. Driving mainly gently with a lot of cruise control, but I'm not a hypermiler and I'm willing to spool up the turbo to climb hills and pass dunces.

    Result" I got 25+ out of the first tank and 26.5 out of the second. Pumping the tires to about 40psi was the only thing I really did for trip prep. This might be the point where I really started to love the RDX again.
  • Its all city driving, like stated, so its stop & go every couple blocks. I did take it to the dealer, and they said its "normal" to have variances between sticker and actual due to the way you drive. Of course it is, but I have an RDX and not a hummer, so these poor results are ticking me off. I wouldn't have gotten such a small SUV had I known it was such a gas guzzler. I was in my friends Mercedes ML350, and I saw her monitor display 17.9mpg. I was astonished. We drive the same places, same city driving, and she's getting much much better mileage on a 6 cylinder much heavier SUV. I got this nice turbo that is sucking me dry. If you guys would buy again, would you get the RDX due to this mileage trouble?
  • depdep Posts: 79
    We are getting 20mpg after 500 miles in 50/50 stop and go + 70mph express way driving.
  • sciguysciguy Posts: 5
    On 9/20/08 I got 24.0 mpg on a 134 mile trip from Irvine, CA to Santa Barbara at an average speed of 67 mph. Light traffic, little or no wind, 3 adults, overnight luggage, roof rack, but nothing on it. All numbers from the trip computer. This car was purchased Dec 2008 and had about 8000 mi on the odometer at the time. My only real complaint about this car is the quirky voice recognition system in the Tech package.
  • novicenovice Posts: 64
    I have a new 2008 RDX, base (owned for 3 weeks). It's Black/Black and shines up beautifully (using Klasse). Early mpg says 24 plus on the highway. 15 plus exclusively stop and go local driving. I expect that once it has 10,000 miles on it, mpg will be slightly better by then. Other than the not-so-great mpg, this car is fabulous, and I view the mpg as one small compromise in exchange for a great drive.
  • dgorrelldgorrell Posts: 1
    On a recent trip between Park City, UT and Sun Valley, ID on mostly (80%) freeway at 75-80 (75 speed limit) my mileage was 23.7 by hand and 22.8 on the tech computer. I use the paddle shifters for almost all deceleration, used no A/C with windows closed and do not do any special tricks to enhance mileage. Fuel used is 91 octane.
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