Where the maintenance and dirtiness were their major detractors, refined fuels and new burners solve these.
Steam engines can and could have been refilled at any gas station, could run on any multi fuel including biodiesel. They theoretically require less maintenance, no oil changes, no cooling system.
They'd also have had greater range and greater top speed (though less acceleration without a hybrid design)
IIRC basic thermodynamics shows that ordinary steam engines can't be very efficient. So, don't get good MPG or miles per bucket of coal, or whatever fuel.
IIRC the main reason for diesel-electric locomotives for trains and large ships was that it was significantly more efficient than just steam, at least steam with just a boiler and pistons.
Of course, really large ships generate steam and then run it through a steam turbine -- no Diesel around.
Stream engines are no longer used on large ships (except for nuclear powered warships). Merchant ships now use large 2-stroke diesel engines for maximum fuel efficiency.
There used to be many large ships driven by oil-fired steam turbines but those have gradually disappeared over the past few decades. Compared to diesel engines, steam turbines are less efficient and require more maintenance.
The most common diesel-electric locomotive today has 6 drive axles. The big steam locomotives designed at their twilight sported 6-10 drive axles, and the most famous and successful of them (the 4-8-8-4 Big Boy) ran 8 drive axles. Mechanical linkage of drive axles isn't what killed the steam locomotive.
Mechanical linkage for multiple direct drive external combustion engines that can operate at 0 rpm is far simpler (the drive axles are basically the crankshaft) than for a single internal combustion engine that must maintain a minimum engine rpm and has to be geared down to axles that are riding on a bogie that pivots separate from the deck of the engine.
To take advantage of the increased efficient of an internal combustion engine you'd need a lot of mechanical complexity unless you go hydraulic (solidly defeating most efficiency improvements) or electric.
> basic thermodynamics shows that ordinary steam engines can't be very efficient
No this is not true, see other comments / Carnot cycle. Steam can be extremely efficient. But diesel engines are much simpler and more compact, it's a trade-off.
The acceleration is more of a function of the powertrain design in steam cars. If you replace the direct drive drive train with one similar to a ICE car (ie clutch+transmission) you can get the acceleration of a ICE car in a steam car. If you want to keep the direct drive though you would need to have a larger engine and use hook-up and variable cut-off to keep the efficiency of the smaller engine while cruising. Steam engines on the whole are pretty similar to electric motors though in having most or all of your torque from 0 rpm which is why many steam cars were direct drive (I think only the Whites and a few race cars had a conventional layout instead of direct drive).
> If you want to keep the direct drive though you would need to have a larger engine and use hook-up and variable cut-off to keep the efficiency of the smaller engine while cruising.
An alternative would be to make hybrids. Use an electric motor to get reasonable acceleration and a smaller steam engine for cruising distance.
Stirling engines have many of the advantages of steam, many of the disadvantages, but they lack the disadvantage of high pressure containment. It's likely that power density would have been too low, however.
A closed loop steam engine, the burners get the boiler hot enough to produce the power they need, then the engine extracts that heat from the boiler to mechanical energy.
Where the maintenance and dirtiness were their major detractors, refined fuels and new burners solve these.
Steam engines can and could have been refilled at any gas station, could run on any multi fuel including biodiesel. They theoretically require less maintenance, no oil changes, no cooling system.
They'd also have had greater range and greater top speed (though less acceleration without a hybrid design)