My Dodge Ram 1500 has 215,000 miles on the engine. These days is sees very little use, maybe 2,000 miles a year if that. It does burn oil but not too bad. I recently put in a quart of Shell Rotella 15W40 diesel oil & noticed it burns less over 500 miles use. I'm thinking of using 15W40 on my next oil change with also a quart or so of Lucas oil mixed in. I don't think I will do any harm on an engine with 215 K on it. The truck is currently used for lumber & material pick up at the local lumber yard only five miles away & sometimes it make a 30 mile round trip into town. Average monthly use is less than 200 miles a month. It's an eight cylinder engine & I think the original oil spec is for 5W20(?). Thanks for the advice / opinion.