I have toyota 2001 corrola. From last couple of days it's driver side door lock gives trouble in opening. I insert key but some times it doesn't rotate. Today morning it didn't open and in the afternoon it opened without any effort. I beleive this is happening because of rust/cold weather. What is good lubricant to lubricate parts that opens door when i rotate key ? Do you have any other suggestion for rectifying problem ?

The best lube for locks is a graphite lube or silicone lube that does not leave any oil residue to collect dust etc. Any auto parts store should have but if not get from a large hardware store or a locksmith.

Graphite is the way to go when lubricating a locking assembly on a car. You can find graphite oil at most auto parts stores for around $6 a can.

You need to determine if this is the problem for starters. If the key is hard to get in, feels rough going in, etc then by all means give it a graphite treatment. If it slides right in and then jambs up there's a good chance the interal lock mechanism is corroded. You can correct this as well by purchasing a general all purpose lubricant. Spray the catch assembly on the inside door jamb and remove the door panel (with window up) and spray the connecting rods that move when you turn the key.

I would say this was electronic but in 01 Toyota still used all mechanical sliders/bars to activate/deactivate the lock.

Good luck!

I believe this is not a mechanical problem but an electrical glitch. Get it checked at ur service station asap.