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Comment by cwyers | Hacker News Reader

I agree, and you absolutely shouldn't replace a car on the basis of fuel economy savings alone. (Having said that, most people aren't junking their old cars if they have a useful service life left, they're reselling them into the used car market.)

But if you compare a new 1998 car to a new 2018 car of the same class, the 2018 car is absolutely going to be better on fuel efficiency and emissions than the 1998 car. And it's not like they got better at fuel efficiency and worse at user maintainability for entirely unrelated reasons; sticking little computers and sensors in things like the fuel injection system is why they're more fuel efficient/better at emissions. (Yes, the little dashboard display is not saving you anything on fuel, it's not 100% related, but they're not fully orthogonal issues either.

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For anyone looking to research that, this[1] video aggregated some source studies. tl;dw: estimates are between 2-17 metric tons of CO2 emissions to produce a new car (SUVs are more). And during operation an average car emits 5.2 metric tons of CO2 per yer.

For a concrete example, a 2021 Toyota Camry Hybrid at 52mpg emits 170g/mile of CO2[2]. A 2000 Camry 4cl at 24mpg emits 340g/mile[3]. Assuming you drive an average 13,500 miles/year[4] the break-even point for CO2 is about 4.5 years.

If you have the 2000 V6 Camry at 20mpg then the break-even is closer to 2.5 years.

[1] https://www.youtube.com/watch?v=6RhtiPefVzM [2] https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=43307 [3] https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=15965 [4] https://www.caranddriver.com/research/a32880477/average-mile...

It also depends on how much you’re driving. If you average say 5k miles per year it’s likely selling your older car is worse for the environment as someone else is likely to drive more. On the other hand people driving 30k miles per year should really be in a very efficient vehicle.

Exactly, rather than getting two new car, I just drive the wifes old less fuel efficient car for those days when I need to go to the office, 15km away. She then got a new more efficient car as she drives 100km per day.

Cars are insanely expensive here, and at 150.000km the car isn’t really in need of replacement. Doing so would also be more environmentally damaging, compared to driving it less than a 100km per week.

Sure, emissions are undeniably better (unless you have a VW, haha) but this is only a net gain if the car gets scrapped, not sold into the used market like you say most people do - that way we have the old smoker still driving around, plus the new one and all its manufacturing costs. The only real gain is for the new car buyers psychologically - they get to feel like they're doing their part, buying their way to a greener planet.

Some number of cars are always going to need to be made new in a year -- due to collisions, wear and tear, etc. It is better for everybody, ceterus parabus, if newer cars are better at fuel efficiency and emissions. It is possible that the number of new cars is higher than it needs to be, but I am unaware of any evidence that suggests it is. Regardless, for each marginal car bought, it's better if that car is more fuel-efficient.

This is the root of the problem. We need to reduce car dependency.

> Sure, emissions are undeniably better (unless you have a VW, haha)

I have a 1985 VW van, so it's haha the wrong direction for me.

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