If you are leaking oil you are going to have 5+ litres along the underside of the car which is going drip where ever you park. Its a lot of oil to lose in a short amount of time. I have a gen4 V6 Camry with 208,000km on it and it doesnt use any oil! As a short term thing the thicker oil is probably worth a try. How many kms have you travelled since the problem started?