I have a Mazda - 323 S V (BA) - 1.8 i 16V (114 Hp) and the data sheet for it says:
Fuel consumption (economy) - combined 7.9 l/100 km.
How is this calculated and under what driving conditions?
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asked Feb 12 '15 at 7:49
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Great question... In short the claimed figures are almost never reproducible under real driving conditions – Zaid Feb 12 '15 at 9:30
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This is an average of the figures for constant speed (highway) driving in top gear and city/traffic driving with lots of gear shifts. The ratio is usually 50/50 so they'll measure e.g. 100 miles of highway driving, then 100miles of city driving, add the figures together and divide by two to get the combined average.
Though to get those same figures, you're going to have to be niggardly with the accelerator pedal. I had a car with a claimed highway consumption figure of 8l/100km and 15l/100km city figure. I managed to improve those figures slightly, but I never went above 2000RPM and I coasted as much as possible and never sped up unless absolutely necessary. If I even momentarily had some fun with the car, the figures went up to 12l/100km and 22l/100km respectively.
So basically the combined figures is the theoretical best figure you'll get if you drive like your grandmother. Though if you drive like a normal person, you can probably add about 20% onto the claimed figure.
answered Feb 12 '15 at 9:49
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1Here recently in the US (last couple of years) there was a change made where US car manufacturers needed to be more accurate what the window sticker said with city/highway driving mileage. I don't know if it is more accurate now than it was, but I believe there are watchdog departments of the government (or EPA) which are checking into the estimates. More of the "truth in advertising" type thing. I believe before it was based on if the engine size is this and the car weighs this much, it should get this mileage. – Pᴀᴜʟsᴛᴇʀ2♦ Feb 12 '15 at 13:16
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I've always been able to replicate or even exceed the claimed figures, but then again I've never owned an American car, so I can't say whether their figures are harder to replicate. – Captain Kenpachi Feb 12 '15 at 13:32
