Is it worth replacing a car engine with a more fuel efficient one?

Discussion in 'Odds & Ends' started by Overdrive, Jul 11, 2013.

  1. Overdrive

    Overdrive Legend

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    I'm not very educated in how automobiles run, but is it worth replacing a car engine (i.e. classic car) with a more fuel efficient engine (i.e Honda Civic Hybrid)? Is it even possible?

    Car afficionados, your welcome to chime in. If it is possible, it sounds like a $4500+ job.
     
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  2. Chico

    Chico Banned

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    Replacing regular engine with hybrid?????

    No.
     
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  3. Overdrive

    Overdrive Legend

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    Ah, that was a bad example. Just replacing a car engine that had 15-20 mpg with an engine that has 30+ mpg.
     
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  4. McLovin

    McLovin Hall of Fame

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    A quick Google search yields an estimated cost of engine replacement of $5K.

    Assuming 15K mi/year and an average of $3.50/gal fuel costs (assuming gas doesn't change much), your annual cost to operate is:
    old engine (20MPG): $2,625
    new engine (30MPG): $1,750

    This results in a savings of $875/yr in fuel costs, which means it will take you approx 5yr 10mo just to recoup the costs of the new engine. So you would have to drive it for at least 6 years to see any cost benefit.

    Now, realistically, it is unlikely you could just 'swap engines' and see that kind of increase in fuel economy. The best example I could see is replacing the engine w/ a diesel engine (compare VW Toureg V6 w/ V6 Toureg TDi), but that would require a change in a ton of other items as well.
     
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  5. ollinger

    ollinger Legend

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    One doesn't just swap engines in and out of today's highly engineered and and highly computerized cars. You would have to know that the engine fits and is compatible with the mounts locations, would likely have to replace the transmission as well since it's engineered for the specs of the engine, and on and on. The cost and engineering problems would likely be prohibitive.
     
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  6. Overdrive

    Overdrive Legend

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    Ah man.... That sounds like just a waste of money then.

    $875 sounds like a decent bundle to save. But diesel fuel? I always see it at gas stations, and it's around $3.85 here. :neutral:
     
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  7. Tamiya

    Tamiya Semi-Pro

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    There are greenie geeks who retrofit their old jalopy with electric drivetrains, if you're after a DIY electric car.

    Or if you have something like an old Merc or BMW that was offered with many different engines, it's not impossible to refit a smaller CC engine off the same model.

    Engine "repower" quite common in poorer countries with cheap wages
    and decent supply of junkers. But if you're paying First World labour
    rates, usually be cheaper to buy another car.
     
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  8. diredesire

    diredesire Super Moderator

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    #1 thing you can do to save money in a car is: fix your right foot. Regulate your speed via the throttle -- brake less (aka read the road more). If you drive a manual, coast in neutral (pulse and glide). You can also inflate your tires more (at the cost of rubber durability). You can easily get 3-5 MPG with very minor driving habits, and that is way cheaper than buying a new/different car/engine/etc. You can also get into the REALLY EXTREME hypermiling techniques such as dimpling your car, installing wind resistance baffles (fins, etc), and 'drafting' (aka tailgating) cars to take advantage of their slipstream (using them as wind resistance baffles). I don't generally recommend any of that, though... Swapping engines is generally very time consuming (labor), difficult (specialized skills), and requires custom fabrication -- unless it's an engine swap in a similar chassis by the same manufacturer (and even this is not always guaranteed).

    As far as diesel fuel, it generally costs more (most) at a station, but if you can achieve gains of 50% MPG with a cost increase of 10% -- it's a no brainer. My TDi Golf has a historical (paper/odometer calculated -- not ECU) average MPG of 46 [This is HWY/City]. So -- If you're forced to buy a different car/engine -- diesel is actually pretty awesome ;)

    I'll also state that diesel vehicles are fun to drive because they have oodles of torque and low RPMs. You are generally driving/cruising at low RPM, which means you've got a ton of pull up hills without having to slam the throttle.

    It should be noted, though, that it's very rarely cost effective to replace a car and expect to save over the 'long haul' just by improving MPG. Most fuel efficient vehicles either hold extremely high resale value, or just straight up cost more up front.

    Edit: I've also been told that gasoline engines these days are more or less operating at their theoretical efficiency peak, and not much gains are going to be realized in the near term without a fuel change. This isn't to say you can't achieve higher MPG, but it comes at a cost. This is either curb weight (which generally is correlated loosely with safety), or power. If American consumers are willing to give up their HP, you could get more fuel efficient vehicles. There are also wonky tricks like disabling cylinders/"fuel economy" modes, etc, but I'm strictly referring to same HP/same power envelope.
     
    Last edited: Jul 12, 2013
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  9. Overdrive

    Overdrive Legend

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    Wow, thanks for this insightful commentary.
     
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  10. Steve Huff

    Steve Huff Legend

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    And, suppose he has a Golf/Jetta which could possibly receive a diesel engine. The engine itself would cost >$5000 installed, plus the cost of new fuel injectors, heads etc. And, you have to consider that your old car has a certain number of miles on it. The engine of a car isn't the only thing to wear out. The more obvious solution would be to trade your car in for the more efficient model you like.
     
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  11. Tamiya

    Tamiya Semi-Pro

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    otoh my neighbor traded their 10yo Camry for a brand new Mazda3
    with idea of saving some fuel $$$...

    But they would've spent $13-15k on the swapover
    and by my books that could've been like 5yrs "free" fuel :(


    Depending on location, there's also option to go gas eg LPG or NGV.
    Conversion isn't too expensive & often subsidized by govt.



    If you're mainly considering the environment, it's better to keep using
    your old car (make sure it's properly maintained & operating like new)
    as long as it can, rather than expend the resources to build another car.
    (Some govts push for new cars... IMHO to prop up local car industry!!)

    Lighten the load, pump up your tyres (I run 38-42psi), avoid short trips
    and renew/vacuum/blowout your air filter regularly.
    Learn to drive smoothly "like you had an egg under your right foot".
     
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  12. Overdrive

    Overdrive Legend

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    Wow, I might as well just leave it alone. I'm buying a new car because they are simply being built to break down on you.
     
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