Diesel gets a bad rap, but petrol (gasoline) is not the best either. They both have drawbacks, but when it comes to generators, you’d be surprised what matters.
When it comes for more bang for your buck, diesel is the clear winner. Diesel is not a very combustible fuel, but it will ignite when mixed with high-pressure heated air. That allows for considerably more power out of a single ignition than what petrol delivers. The downside to this approach is that the ignition of diesel can’t be controlled as finely as petrol, but that’s relevant to something like a motorcycle, not a generator.
Petrol engines are lighter, which is why you are more likely to encounter them in portable generators. The problem with diesel is that it can’t be controlled as accurately as petrol. A spark plug times the detonation of petrol in the engine, while diesel ignites randomly. The result is a lot of shaking, so diesel engines need to be more reinforced and thus heavier.
No doubts here: if you want volatility, petrol wins. It takes very little to set petrol off, whereas diesel is far more docile. The difference is in how they mix with air – and petrol is like an office party after the third round. This explains why spilt petrol is very dangerous: it can even be ignited by heat. Diesel won’t even respond to an open flame.
How do you know there’s a diesel engine at the door? It just keeps on knocking. The distinct thud-thud-thud of a diesel engine is its calling card. This goes back to the compression process that causes diesel to combust. Because the combustion is spontaneous, it never happens at exactly the same time. The result is noise, in particular a low ‘thud!’ sound that travels further than higher pitches such as a petrol engine’s whine. Diesel generators should come with sound-dampening housing. On the other hand, some people find them hypnotic. There are even, believe it or not, 12 hour long diesel engine videos:
The rule is that diesel engines should be serviced twice as often as petrol engines. This is true for vehicles, but diesel generators are actually quite more resilient than their petrol peers. They generate less heat and as a result less wear on the parts. This is also why diesel engines can run for longer without risking damage. Another diesel benefit is it stores better. Diesel can last between six months and a year, while petrol is reliable for roughly half that time. Petrol is also more likely to evaporate (and cause a fire hazard) because it mixes readily with air.