If the engine sounds like it's about to blow up, it's either time to shift up into the next gear, or if you're in top gear... slow down. :hysterical:

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The appropriate time to shift will depend on the engine and situation. For smaller gasoline engines, it's more appropriate to shift up at around 2500-3000 rpm (as long as the gears aren't incredibly long), while bigger gasoline engines and diesels will feel comfortable shifting up at 2000-2500 rpm.

On most cars you start in 1st gear... on some you can start in 2nd (L300, anyone? :hysterical ) with no problems.

There's no golden rule. In my old 1.3, I was in 4th by 50 km/h. In my 2.0, I'm in 5th. In the Focus diesel, I'm in 6th... ...as long as the car isn't lugging (naghihirap... or nagkakabayo...)... then you're in the right gear.