Walmart had 5qt juggs of Pennzoil High Mileage 10w40 on clearance for $9 and Pennzoil Euro Formula 0w40 for $13. I almost bought them with the intention of mixing them to run in my 91 K1500 with 4.3 V6. It is spec'd for 5w30. It has enough wear that the 40 wt won't hurt it. But, I have five 5qt containers of Havoline HM and one 5qt container of Pennzoil conventional. That's enough for 3 years in my truck should I keep it that long.