You shouldn't be using a 40 weight oil on an LS1 unless it has a ton of miles on it (I mean A LOT) and the engine is worn out. I had to do this with an old Hyundai Accent. After I switched to a thicker weight oil, the oil consumption went away. The previous owner didn't maintain the vehicle well.
The '94 Passport 4 and 6-cylinder both use an EaO20 oil filter. This filter is to be changed every 1-year or 25,000 miles, whichever comes first.
Amsoil recommends either 0W30 (product TSO), 10W30 (product ATM) or product 5W30.
The 0W30 is supposed to be changed every 1-year or 35,000 miles, whichever comes first.
The 10W30 is supposed to be changed every 1-year or 25,000 miles whichever comes first.
Just so you don't think I put a typo for the 0W30 and meant 3,500 miles, I just took a picture of the back of the label on the bottle. It says to change the Amsoil filter every 12,500 miles, but that was before they came out with their new EAO oil filters. The SDF filters has to be changed every 6-months or 12,500 miles. They no longer sell the SDF filters. They need to update their labels.
Here's the label on the back of the bottle. They even proudly show some of the competition on the back. I don't know of ANY oil company who would do that. They couldn't put that stuff on back unless it was true.
As you can see, Mobil 1 rated as one of the worst. People just keep using Mobil because they buy into their massive advertising. I know I did. How are you supposed to tell unless somebody went and paid big bucks for an independent test. Amsoil did. They paid a 3rd party company to analyze a bunch of the most popular oils.
I spoke with another guy who owns a Ford Explorer. He went from 19 to 21 MPG after switching to Amsoil. Not a bad deal. The gas mileage ends up paying for the oil. Amsoil costs me absolutely nothing now because of the massive savings I'm getting on fuel.
I have over 20,000 miles on the same oil right now and my gas mileage is still great. I changed the filter a few days ago. Some of the old oil came out with the filter. There's absolutely no sludge at all. The oil still flows perfectly. I can't wait until I hit 35,000 with it or 1-year. I want to get the oil analysis done.
Who do you guys recommend to do the anaylsis?
Also... one thing to keep in mind... You'll notice that other synthetic oils always compare themselves to "Conventional Oil" in their ads. Amsoil didn't wimp out here. To keep things on a level playing field, they compared themselves to OTHER SYNTHETICS. Any synthetic will be better than conventional oil made from crude oil. Amsoil blows away ALL conventional oil AND ALL other synthetic oils. If you would have talked to me about these 5+ years ago, I would have told you I thought they were all the same. Back then, I did absolutely no research.