Join Date: Feb 2019
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Like most of you, I have complained about the mpg of my new 2019 QX50 Essential Sensory being so far off from the promiseof the EPA’s 24/30, combined 26 mpg ratings. The Consumer Report study some of you cite says those numbers are inflated by 15%, using their track simulations test process. But what should I expect to get in the real world? Some facts:
What is the EPA test? Their web site says:
“The "city" program is designed to replicate an urban rush-hour driving experience in which the vehicle is started with the engine cold and is driven in stop-and-go traffic with frequent idling. The car or truck is driven for 11 miles and makes 23 stops over the course of 31 minutes, with an average speed of 20 mph and a top speed of 56mph. The "highway" program, on the other hand, is created to emulate rural and interstate freeway driving with a warmed-up engine, making no stops(both of which ensure maximum fuel economy). The vehicle is driven for 10 milesover a period of 12.5 minutes with an average speed of 48 mph and a top speedof 60 mph. Both fuel economy tests are performed with the vehicle's airconditioning and other accessories turned off.” It further says the combined rating is the weighted average of 55% cityand 45% highway.
I must say that my “city” driving is not that slow/stop and go, so the typical 22 mpg I get is maybe not so comparable (although it is far far better than the CR report’s 15 mpg measurement!!) A better test for me is my recent extended highway trip. I went 250 miles with cruise control on 65 mph in one direction, and then returned doing 75 mph in the other. The trip included going over a 3000 ft mountain and foothills, so not a flat ride for about a third of the trip. And the air conditioner was on. On the first leg I got 29.8 mpg, and on the return I got 26.1, as measure by the car. When I did the actual calculation, it was actually 7-9% lower (another disappointment, but that’s another story) at 28mpg (9% below the predicted 30) and 25 (17% below 30).
I then researched the effect of speed on mpg. I found several studies saying that versus driving at 50 mph (the EPA’s test speed), driving at 60 mph decreases mpg by 3-7%, 65 decreases it by 8-15%, 70 by 17-24%, 75 by 23-34%, and 80 by 28-42%. A lot. My experience was at the low end of or below those ranges.
Then I compared the QX50 EPA ratings to those of 6 competitors: Audi Q5, Acura RDX, Volvo XC60, Mercedes GLC300, Lexus NX300 and BMW X3. All had ratings a good 8-12% worse than the QX50, and presumably they too actually perform a least a bit below their ratings (CR says so, too). And of course they should be similarly impacted by driving speed. But my actually performance was about what their ratings are even though I was driving a lot faster!
My conclusion is that the QX50 indeed delivering on the EPA mpg ratings promise when you include the impact of speed, and it is doing at least a bit better than its competition. Now if I could just get myself to drive as slowly as those EPA tests!! Meanwhile, I will quit complaining now.