I've been using light oils like Wd40.
Do not use WD40 on firearms. Period. Now, I'm sure someone will post here saying they've used WD40 for years on their guns and it's OK for the purpose. But guess what. They're wrong.
Now that we've cleared that up, here is the best and most thorough guide I've seen for how to properly lubricate your Garand for maximum life and performance: