alt Hacker News25 years ago in the UK, leaded petrol was being phased out but still pretty common. The UK Government was giving people grants to have existing cars converted to run on LPG, so they'd only run on a coke can of petrol for a minute or so on startup then switch over to gas.
Catalytic converters? Don't need 'em! There's no CO or unburnt fuel in the exhaust to catalyse because they run as lean as a vegan's dog!
CO2 emissions? Sure, but the stuff is getting flared off as waste at refineries anyway, and we're not going to stop making plastics and fertilisers any time soon, so may as well extract useful work from burning it!
We could have had incredibly clean cities everywhere by now, by simply keeping older cars on the road and adapting them to run on much cleaner safer fuel.
But there was a problem, an absolute bombshell of a problem. The fatal flaw that killed LPG as a road fuel.
It didn't sell new cars. It didn't sell anyone any debt.
So they came up with "scrappage schemes" where you'd get a couple of hundred quid for your old car, it would get destroyed, and then all you had to do was buy a nice new Cleaner Greener Diesel car instead, at some swingeing rate of interest (expect to pay well over twice the sticker price by the end of it - and no, you didn't get the Scrappage Scheme cash if you didn't take the finance package).
And you see how well that worked out.
LPG had the same problem as electric cars. In the early years there was no infrastructure and so if you buy one you're an early adopter and you can't actually go anywhere. It took a while to get that infrastructure and now electric cars are useful for most trips. You can use LPG cars to go for most trips in the US even today. However, you better plan ahead because finding a place of fuel is going to require some effort. I had a few LNG stations near me, but they seem to have all been torn out, meaning that never made it.
Gas cars faced the same thing when they first came out but by the time they became used for longer trips there was gas everywhere and in the meantime there was gas at least where you bought the car and so it was good enough for the short trips that bought it for.