What if you stupidly bought cars that get poor mileage years back and recognize that this was a mistake, but now being more environmentally and fiscally conscious you also want to use products for as long as possible? Sure, I'd love to get better mileage, but there's a lot of energy required to create a vehicle as well. Just like I don't want a yearly phone upgrade because my current one is good enough, I also want to space out my auto upgrades as long as possible.
Here's my car situation. I bought a 1995 Ford Windstar in 2002 with about 90K miles for $4K. Today it has 175K miles. It gets about 19 mpg (not bad relatively speaking). It did get a new transmission in 2003. Otherwise it's been pretty good to me. It has new tires and brakes right now. KBB says it's worth $1500. I bought it thinking I would have maybe 4 kids, but I ended up with only 2, so it's not necessary that I drive a car this large. I put about 6K miles/yr on it (this has come down through the years). Work is relatively close (12 mile daily commute round trip). I do bike when I can.
My wife drives a 2005 Honda Accord V6 that we bought in 08 for $13K. It also has 175K miles. It has also had the transmission replaced. My wife does not work, but we home school and that means she drives a bit more than me. Not terrible. 10K miles per year. It also has new brakes and tires. It gets about 25 mpg. KBB says it's worth $5600. With the exception of the transmission problem it's been a very reliable car for us and retains a high quality feel. We are happy with it in that regard.
I have been tracking my expenses carefully this year, and I found that my total maintenance/repair costs for the two cars has averaged $209/mo. Insurance is $140/mo (full coverage on the Honda, liability only on the Ford).
How do you evaluate this so as to consider mileage, upgrade cost, and environmental impact of the upgrade? There's no reason we can't get by with smaller cars getting more like 35 mpg each, but on the other hand changing realistically means newer and that's contrary to my desire to resist the constant upgrade mentality that is so common. Naturally my next cars will have to be newer.