What has a lesser carbon footprint? Continue to drive my current car until it is no longer useful or to buy a new car?

Question

I have 2003 Honda Accord. It gets ~20 MPG CITY (8.5 km/liter). I'm trying to figure out if it is more sustainable in the long run to:

• continue to drive the Accord until it dies (it's still in great shape right now). I will continue to use gas and get below avg MPG.
• buy a fuel efficient gas engine car. I will continue to use gas and get better gas mileage
• buy a fuel efficient hybrid car. I will use less gas and get a lot better gas mileage
• but an electric car (my daily commute is ~20 miles (32 km) round trip). I will NOT use gas (MPG does not apply here)

The other thing I don't know how to factor in is the environmental cost that goes into producing a new car. If I buy a new car, I should factor this cost into how sustainable my decision is.

Answer 1

I cannot give an answer for your car specifically but I found an interesting study (Spielmann & Althaus 2006) exploring the options of buying a new car or continue on using an older model for Swiss passenger cars. It is concluded that a

"prolonged car use [is] the environmentally better option. As a consequence of the continuous use of the car representing 2000 average technology, the components ‘vehicle travel’ [includes "exhaust and abrasion emissions"] and ‘fuel chain’ ["supply of fuels"] show a 10% and 9% [worse] performance, respectively. This effect is compensated by savings in ‘car infrastructure’ [manufacturing, maintenance and disposal of cars] (26%).

I'm surprised that there is not more of a difference. In simple words; it is more "sustainable" to use your car until the end of its lifetime (15 years of use as opposed to replacing after 5 years - as defined in the study).

Reference: Spielmann M & Althaus HJ 2006: Can a prolonged use of a passenger car reduce environmental burdens? Journal of Cleaner Production 15 (2007) 1122-1134. http://www.sciencedirect.com/science/article/pii/S0959652606002514

Answer 2

It doesn't depend on how much you drive, although it may depend on where and how you drive. I would argue that the best use for almost any vehicle is to use it until it is worn out. If it is running when you sell it, the next person is going to drive it, not scrap it. There is a very large 'embodied energy' in a car. Energy used to make the steel, run the factory, ship it to you. SOMEONE is going to finish using that car up. If it is to your economic advantage to be that someone, do it.

If you are comfortable with this, then the next concept is that it's better to own or at least use the most appropriate vehicle for the task at hand.

Example: Right now our household owns a subaru outback and a chevy silverado. The subaru gets almost 8 times the yearly miles on it that the truck does. But the truck can haul a lift of plywood or 100 trees in #2 pots. (I'm a tree farmer)

If you have room, then your best strategy may be to keep the accord as being a roomy enough car for holidays, buy a hybrid for the daily commute.

Medium efficient car vs small inefficient car.

Look at the total lifespan of the vehicle. Depending on the numbers, the Medium car may be overall cheaper. Or not. As a rule of thumb buy the smallest car that will do the job. But don't blind yourself to a used car. Also look at the lifespan of the car. A cheap small car that has to be replaced at 100,000 km is not a win. Consumer Reports is THE goto for this sort of information. They have figures for TCO for the first 5 years of ownership of almost every make out there. While there is a difference between 5 years and TCO the first is a good indicator of the second.

Hybrids vs Diesel

The Europeans are getting good at making small diesel cars that get better gas milage than hybrids. This is a multifold win: Diesel is easier and less energy intensive to make than gasoline. Diesel gets better mileage = less carbon burned. Diesel engines tend to last forever. Unfortunately these cars are not marketed in North America, mostly because they require lower sulfur diesel.

Hybrids vs All electric

Where does your power come from? If you are using coal fired generators to charge your car, you are only exporting your carbon footprint. And over all coal is worse than oil this way. In addition at this point the technology used for all electric isn't sustainable. There isn't enough lithium to make all the required batteries. The hybrid uses batteries only as a load leveling device. Overall the engine runs more efficiently at a more constant speed.

Added: 2019-Feb-6

Lithium seems to be ramping up just fine. Current battery issue is cobalt, much which comes from Republic of Congo with badly treated workers. EVs and Hybrids are still at this point about a 3-7 year ROI in terms of ownership.

In the long run EVs should do better. An electric motor is simpler and lower maintenance than an ICE. So the drive system should last a very long time. Li-Ion batteries last a few thousand cycles, so will need to be replaced about once a decade. (Guessing 50% charge used daily = 4 years per thousand discharge cycles)

If I had to make a purchase by Tuesday, I'd do a diesel. By 2024, I would hope to make that electric. But at present I live in a harsh winter climate an hour's drive from true civilization.

Answer 3

I don't know an answer to your question, but I think it depends on how much you drive. I would imagine that a car that is in good shape is best used by someone, who needs a car, but doesn't drive very often and not for very long distances. Like an elderly person, who only uses the car to go shopping at the store 3 miles away, maybe twice a week. If that's you, you should probably keep the car ;)

If you drive every day, then it might be better to sell the car to someone, who will not use it everyday and for long distances. Of course, once you sell it, you have no control over how the car is used, but it's probably worth using the car to the end of its life-cycle.

You can also try to increase your fuel efficiency. Until recently I drove a usually fully loaded 2001 Renault Clio (Limousine) with twice the efficiency (5.5l/100km = 42MPG) (only city as well).

We have discussed some strategies here: How to drive to be the most fuel efficient.

Answer 4

This: buy a fuel efficient hybrid car. I will use less gas and get a lot better gas mileage, but do ensure you can charge your hybrid car! Many hybrids have a tiny battery and can't be charged. So I'm proposing to purchase a plug-in-hybrid electric vehicle (PHEV).

If there's even one coal plant producing electricity in your area, every energy user is equally guilty of the coal plant being turned on.

By purchasing a hybrid car, you can charge it when electricity is cheap (windy days), and drive using gasoline when electricity is expensive (non-windy days, plenty of coal power being used).

Generally speaking, ~10% of a car's lifecycle emissions come from manufacturing the car. With coal-fueled electricity, an electric car is actually worse in producing emissions than a reasonably efficient gasoline-powered car (although your current car seems to be very inefficient user of energy). With wind-produced electricity, an electric car has zero emissions.