With gasoline being sold at $3 per gallon and higher, it's a valid question.
I posted a comment in answer to her question which I will share with you, along with some further thoughts on transportation costs today.
I used to be a "member" at National Public Radio and Public TV.
I quit contributing to NPR when they became a broadcast arm of one of our political parties, but I freeload by continuing to listen to some of my favorite programs.
As an auto enthusiast, I enjoy "Click and Clack, The Tappet Brothers".
Some time back the boys discussed the point at which a car will get the best gas mileage. This happens when the engine is turning at the slowest RPM in it's top road gear..........4th gear in a 4 speed transmission. At this point you are using the least fuel to cover the most distance. Go faster, and you incur higher wind resistance, (drag), and mileage will decrease.
This speed is easy to discover in a car with an automatic transmission......accelerate slowly and watch the tachometer (or just listen) for the transmission to make that last shift, and note the speed.
With a manual transmission you need to consider the slowest speed your car will go without bogging the engine down.
Tire pressures are also an important factor. Higher pressures mean lower rolling resistance and better mileage, but also mean a sacrifice in ride quality.......the car will ride rougher.
I've been experimenting with our car on the way to work. My trip is 35 miles, with a small town about midway where I have to make 3 stops at stop signs.
I found that our 4300 pound car with automatic transmission shifts into top (4th) gear at 40 miles per hour when I am accelerating gently.
I also found that if I tried to drive at that speed, when I encountered a hill along the way, the tranny would downshift to third to climb the hill, therefore less miles per gallon.
Adding 5 m.p.h. to the speed.........45......... precluded this from happening.
I reset the onboard computer as I drove away from home.
When I got to work, the computer indicated 32.8 miles per gallon!
Not bad for a 4300 pound car with a 253 horsepower, 3.5 liter V-6!
Of course, driving at 45 m.p.h. needs to be factored into my plans for making it to work on time, but at $3.00 per gallon, I have the incentive to take the extra time!
An electric car would be an attractive option. I could recharge at home, then plug in at work and recharge for the drive home.
There are cars that can range out as far as 35-40 miles at 50 miles per hour, so that wouldn't be a problem.
But the kits for these automobiles run about $7,000, and for that money I can buy a lot of gas, even at $3 per gallon!
I've also been looking at Diesels. They get better mileage than a comparable gasoline auto, and the old complaints about them.....noise, vibration, and smell........are less and less a factor with the newer vehicles.
But I found an interesting thing: you can run them on vegetable oil!
Many penny pinchers are now going to restaurants and offering them a win/win situation: Let me have your old deep frying oil, and instead of having to pay to have it hauled off, I'll do it for free!
But as usual, there is a catch here too:
Diesel engines won't start on the vegetable oil.
The solution is to have two fuel systems on your vehicle.
Start the engine on Diesel, then switch to the vegetable oil system.
BUT, you must remember to switch back to the Diesel system before shutting the engine down in order to be able to start the engine the next time!
Vegetable oil conversions can be purchased for less than $1,000, if you decide you'd like to cut back on costs this way.
Another viable alternative is Natural gas/Propane.
Any gasoline fueled car can be converted to burn Natural gas or Propane. Adjustments need to be made to the fuel injection and engine control computer, and the fuel storage system needs to be adapted to your individual vehicle.
Costs will vary depending on how much your vehicle needs to be modified, but the cost of using Natural gas/Propane instead of gasoline at $3 per would make the changeover worthwhile in a very short time!
Gas prices are headed back down as I write this, thank goodness!
But fuel costs are now on everyone's mind, and I suspect we'll see a change in attitude when people go to buy a new car/truck in the future.
As for me, until I'm ready to buy my next new car, I'll be driving to work at 45 miles per hour!