If you're doing all or mostly short distance petrol is likely to be better bet unless you're looking at cars over 10yrs old.

"Most of the answers to your many questions can be found in the Beano..."

Unless you are absolutely sure the OP was a wind-up, this is a patronising comment (thank goodness, the only one so far).

From the Chambers dictionary :

geek

n a circus or carnival freak; a strange or eccentric person, a creep or misfit; someone who is obsessively enthusiastic, esp about computers.

[British dialect geck a fool]

geeky adj.

I think it may be necessary to change your alias to stop the snide remarks.

We all learned something along our respective lines. The main difference between petrol and diesel engines is that the petrol engine uses petrol, which quickly evaporates if you spill it, and the diesel engine uses diesel oil, which doesn’t. If one is clumsy on the forecourt and spill fuel, petrol is quickly gone, but diesel oil gets under one’s feet and the feet of those that follow you at the pump. Also, if you get diesel oil on your hands it smells for a long time despite washing.

The engines in lorries buses and trains are almost invariably diesel.

The difference between the two types of engine in cars is that the diesel is marginally more fuel efficient but more polluting.

In the long term diesel engines need more spending on them.