Got the bad news today.....my 300,000 mile truck has two cylinders that are way under minimum spec compression. This is like hearing a family member has cancer. I've had this truck for 16 years. So before I start looking for a new engine, I thought maybe I'd try some thicker oils in a hail Mary attempt. The manual calls for 10w30. So should I go 10w40, or go for the gusto and buy some xw50?