I just added 5w20 to my 94 civic that recommends 5w30. It should be ok because being in upstate new york it gets real cold and can change it out in the spring. but is there any real harm in doing this?
No… Not in that climate. When temperatures warm up to around 70 degrees, I would use 10/30. 5/20 is FINE in the winter months…
You’re good. Your Civic will do quite well on 5W20 until spring. You have the right climate for it.
I agree, Even if you had changed the oil to 5W20 it will be fine until spring. If you just added some because the oil was low, then you don’t need to change it out in the spring unless it is due then anyway.
5W20 will give you a little better mileage and maybe even a little better lube during the winter. Likely too little to notice.