[the_devils_advocate_666]

an combustion cycle
an fuel injection event

Somebody please clue me in again on what the rules are for "an" versus "a".

[bmwcyle]

My mother would have been upset with the two items.

[Quality_Not_Quantity]

'An' precedes words that start with a vowel sound.

There was a Monty Python episode once where one guy asks the other to hand him 'an hoop', over-exaggerating the normally-silent 'H' sound. Needless to say, the other guy mocked him mercilessly.

[jonascord]

If the next word starts with a consonant, go with a. A crow.

If it starts with a vowel, (a,e,i,o,u), use an. An owl.

It'll sound right 99% of the time. I read it aloud in my head before I hit "Post." If it doesn't sound right, I'll double back and try to find where it clangs like a dropped anvil.