Bought oil for my Integra and my wife's Corolla a couple of weeks ago. I just put the oil in the Corolla last night, only to look down and see I had just put in 5w-20 instead of the 5w-30 the car is supposed to get. Any possible issues driving on a thinner-weight oil for about a week or so?

 

Wife's car, so probably not driven hard, so probably no issues.

Besides, it's nearly winter, and 5w-20 is recommended for winter use by the manufacturer in many cars that normally make use of 5w-30 in the summer.

I wouldn't worry about it.

 

This is for an 09 Corolla but your owners manual should have something similar. It'll be fine, some people run 0W30 in cars that call for 5w30 so don't sweat it:

 

Yea I've been running 0w-30 Mobil1 synthetic in my Integra for 2 years now.