My son has a 2000 Focus ZX3. He went to Oreilly to get some oil and filter the other day, and came back with Castrol 5w20. He said they told him that 5w20 or 5w30 is appropriate for this car, but the book calls for 5w30. We proceeded to change and use the Castrol 5w20. Is this going to be OK for this car? We live in N.C. and we don't have a lot of sustained cold weather here (Usually anyway). thanks for your input