Originally Posted by floater3
My 2000 owner's manual specifies 5W30. I wonder why they would make that change in the next year? I'm thinking the tolerances woudn't change all that much but maybe there is some other technical reason. As Bert noted, it's probably for the pursuit of the CAFE standards.
You're probably right on that.
I do notice though that looking at the spec sheet (Haynes for what it's worth) it shows the 1999+ engines got 40-70 psi oil pressure, up from the 20-40 psi of earlier versions,nearly twice the pressure.So maybe the engineers intended the higher pressure combined with a thinner oil to correct an oiling problem they were encountering such as insufficient lubrication at start-up.
Also in 2000 the piston ring side clearance and end-gap were tightened way up and the piston to bore side clearance '97 up was MUCH
tighter (.0008-.0018 then '97 and later; .0002-.0010) which is a huge difference. -Brian