I have a leftover quart of Mobil 1 5W-30. I'd like to switch over to a 0W-30 or -40 for the next OC for better cold performance. Mobil 1 gallon jugs are on sale for $19.99. The Subaru takes 4.2 quarts. Can I put in 4 quarts of 0W-xx and top off the remaining 200 mL with the extra quart of Mobil 1?