[apexalpha]

>Once a car is light and small(ish) the good MPG will follow. My 1988 Volvo 240 got 30mpg on a recent road trip and that's with it needing a tune up.

Doesn't this work both ways? If you focus on MPG then lighter, smaller variants of the same model will win out over bigger, heavier ones.

[LarryDarrell]

To a certain extent, yes. I'm mostly daydreaming about if you magically remade my little Volvo with modern materials and one of those low-displacement turbo engines they put in cars today. It would be 500 pounds lighter with 3 times as much horsepower.

But... that car would be a dud today. It's too simple and lacks features (like power seats).

[mrguyorama]

Also crashing into anything would kill you. Modern safety standards are very heavy.

[sidewndr46]

What does weight matter on a road trip? Unless you are exclusively driving at 30 mph uphill I don't see it mattering much. Wind resistance is the dominant force. This is the same reason why most railroads put limitations on the maximum grade they have to climb. They are mainly working against wind resistance, not gravity.

[aidenn0]

There are two numbers on the sticker for fuel efficiency. In-town and highway.

For in-town weight matters greatly (both because you essentially throw away energy every time you break, and because rolling-resistance matters more at low speed).

For highway, up until 2008 the maximum speed tested was 55, which disadvantages heavy-vehicles, as rolling resistance is a higher component of energy used at lower speeds (as a simple approximation, rolling-resistance is linear, and air-resistance is quadratic).

[sidewndr46]

The thread was specifically about a road trip. I can't imagine anyone taking a road trip entirely in town.

[bialpio]

Driving around Yosemite or Yellowstone is gonna be closer to in-town riding than to highway riding. I wouldn't be too surprised if time spent on driving at the destination was ~50% of my driving time at some road trips I took.

[aidenn0]

I've done road-trips entirely off of limited-access highways.

[_Microft]

Road damage scales with fourth power of axle load.

A car that is 50% heavier does 5 times the damage.

https://en.m.wikipedia.org/wiki/Fourth_power_law

[sidewndr46]

The thread was about fuel economy on a road trip.

[apexalpha]

>Wind resistance is the dominant force.

Hence, smaller cars have better MPG. Smaller cars also tend to be lighter.

[Symbiote]

Railways have very low gradients due to the limits of friction of steel wheels on steel rails.

[jusssi]

Heavier vehicle puts more work into deforming the road. It must follow it also puts more energy into that.

[bobbylarrybobby]

Yes, but no, because the MPG standards in the US are on a per-size basis. I forget exactly what, but it's per weight, or per footprint (m^2) or something else that lets you shrink the ratio by just building a physically larger car.