Hi All!
Want a viscosity recommendation for this particular vehicle/situation:
1995 GMC 2500 with 454/4L80E; 200K mi, runs like new.
My daily commute is 7 miles, noticed last oil change and the most recent (15-40 Delo LE) (this is a flat tappet engine after all!)
Observations:
1. Oil pressure at start up goes to 65psi. Doesn't matter if in gear at 800rpm or neutral at 1200.
A. Is this at the bypass pressure, allowing oil to bypass the filter? This condition remains constant for 4-6 miles, at which time idle oil pressure drops to 40psi in gear.
2. After approximately 7 miles (in 90 degree plus heat), idle oil pressure drops to a steady 25psi at 700rpm in gear. Oil pressure above 1400rpm stabilizes at 60psi. These remain constant even after a highway run of 20-30 miles at 60mph, so I conclude the oil temp has stabilized. This vehicle was ordered with an engine oil cooler from the factory, max towing pkg. Towed 1500 lbs MORE than the diesel in 1995! 14 bolt rear, 4.10 gears, etc.
3. Given that 90% of my driving is to and from work, if 65psi is where the bypass opens negating filtering, a goodly portion of my daily drive is with the oil "unfiltered".
4. Would it be reasonable to change to a 0W-30 or 0W-40, given that the 40 is good after warming but the cold 15W seems to be too viscous at start up to NOT bypass the filter?
Opinions appreciated! All considered!
Kyle
Want a viscosity recommendation for this particular vehicle/situation:
1995 GMC 2500 with 454/4L80E; 200K mi, runs like new.
My daily commute is 7 miles, noticed last oil change and the most recent (15-40 Delo LE) (this is a flat tappet engine after all!)
Observations:
1. Oil pressure at start up goes to 65psi. Doesn't matter if in gear at 800rpm or neutral at 1200.
A. Is this at the bypass pressure, allowing oil to bypass the filter? This condition remains constant for 4-6 miles, at which time idle oil pressure drops to 40psi in gear.
2. After approximately 7 miles (in 90 degree plus heat), idle oil pressure drops to a steady 25psi at 700rpm in gear. Oil pressure above 1400rpm stabilizes at 60psi. These remain constant even after a highway run of 20-30 miles at 60mph, so I conclude the oil temp has stabilized. This vehicle was ordered with an engine oil cooler from the factory, max towing pkg. Towed 1500 lbs MORE than the diesel in 1995! 14 bolt rear, 4.10 gears, etc.
3. Given that 90% of my driving is to and from work, if 65psi is where the bypass opens negating filtering, a goodly portion of my daily drive is with the oil "unfiltered".
4. Would it be reasonable to change to a 0W-30 or 0W-40, given that the 40 is good after warming but the cold 15W seems to be too viscous at start up to NOT bypass the filter?
Opinions appreciated! All considered!
Kyle