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Thread: economy for diesel CX5 manual

  1. #1
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    cx5

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    economy for diesel CX5 manual

    I assume that to get the best economy from a CX5, you want steady speeds and minimal braking. But what speed is best for a diesel manual version to get that economy? Is it cruising at 70mph (ie up and down motorways) or going at 50-60mph (rural inter-city roads) or perhaps going at 30-40mph (suburban roads)? Has anybody published figures? Or has anybody experimented with this?

  2. #2
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    2013 Mazda CX-5 Sport FWD Auto

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    You lose fuel economy at speeds over 55-60 mph. Steady as possible at 55 mph with a light touch on the accelerator. Air starts to drag on the car and reduce mpg at speeds higher than that. Accelerate slowly from stops. Think big toe on an egg type acceleration. Engine break as much as possible. Brake dust is lost fuel economy. You can do better than cruise control as you can anticipate slight drops or rises. Cruise control accelerates too harshly up hills and it canít anticipate drops either.

    Thatís about all there is to it. Look up hypermilling if youíd like to learn more. Itís not much fun but itís absolute best case scenario if maximum mpg is your goal.

    Credentials: used to do this in my 98 diesel Jetta. Best I got was 60 mpg over a tank. 55 mpg if I was trying somewhat. 45-50 mpg if I didnít care.
    Last edited by ruthrj; 05-07-2019 at 11:19 AM.

  3. #3
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    Most cars get their absolute best mileage in the range of a steady 40-45 mph. This is the "crossover point" where the increase in drag overcomes the inherent losses of the engine running at very low power levels. It's also the point where most cars will shift to their highest gear and you want the engine turning as few RPMs as possible for a given speed to get the best mileage. But the peak is very flat, so anything between 30-mph and 55 mph will be very close..... it is only when you start going over 55-mph or so that drag starts to rise enough to seriously affect mileage.

    As previous poster mentions, the big key is to avoid using brakes and accelerate lightly so the car stays in a high gear without having to downshift. If terrain is rolling, then letting your speed bleed off up hill and speed up downhill is better than trying to maintain a steady speed. Again, avoid braking at all costs.

    - Mark
    Last edited by markjenn; 05-08-2019 at 02:37 PM.

  4. #4
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    was 175ps Mazda CX-5 Auto AWD Sport Nav, now 190ps DSG Tiguan 4M

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    It also helps if the car has an eco mode which can disconnect the gear box, effectively running in neutral at tick over.
    And having extra gears so the engine is always running at its most efficient.

    Speed wise ironically I've found an average higher speed (but still low) can return better economy, my car has an app which shows each journey (VW).

  5. #5
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    I get the best mileage when I use radar cruise. I'm guessing its smarter about matching the shifting to the desired speed, and also assume it uses engine braking over friction when practical.

  6. #6
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    13' CX-5 and 16' Mazda6 both Touring w/Tech/Bose

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    Quote Originally Posted by markjenn View Post
    Most cars get their absolute best mileage in the range of a steady 40-45 mph.

    - Mark
    Quote Originally Posted by murky View Post
    I get the best mileage when I use radar cruise. I'm guessing its smarter about matching the shifting to the desired speed, and also assume it uses engine braking over friction when practical.
    My cars tend to like cruise control at 52mph in terms of max mpgs to real world usable speed ratio.

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