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SUVs Acura RDX Acura RDX Real World MPG
189 messages, Last post on Nov 08, 2009 at 3:44 PM
You are in the Acura RDX Forum. Your Hosts are steve_ & tidester
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Replying to: oncrank (May 15, 2007 2:47 am) |
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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. |
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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.
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Replying to: oncrank (May 16, 2007 3:26 am) 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.
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Replying to: c_hunter (May 16, 2007 5:41 pm) 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. |
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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. |
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Replying to: wkrd09 (May 12, 2007 8:28 pm) 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.
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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.
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Replying to: mjo1 (Jun 21, 2007 11:02 am) Rich |
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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. |
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