Can anyone explain to me about the oil weights viscosity required for the 98 Chevy Silverado DWR with the 454 cu in and my mileage is at133000 miles.

My co-worker suggested on my next oil change I should get this viscosity SAE 20W-50 or a 40 weight. He says it is better for the big blocks and gives the motor a longer lifespan.

Is there any truths to this?

I am currently in California and will be moving to Portland area in Oregon, different climates and which will affect it.

Dave

 

I would stick with the manufacturer's recommendation assuming the motor is running well with good oil pressure and not burning alot of oil. Portland OR is not really a big climate change vs CA and the manufacturer's rec will be fine.
BTW welcome to the great Pacific NW!

 

And what basis is he using to suggest that a 40w or 50w oil will increase longevity? That sounds like that nonsense that Lucas Oil Stabilizer will do wonders for a motor. Both of these solutions could help, if you motor is already on it's last leg. 133K could hardly be considered about the end of it's useful life. If you are not having oil consumption issues now and the motor is doing fine, don't go to a heavier oil.

Just use a good quality 5w30 and call it a day. I was always partial to using a synthetic blend 5w30 in my '98 454, but that isn't critical. From purely a technical point of view, what really helps out the 454 is a quality oil that has a healthy dose of molybdenum (moly) in it. Moly is one of the best substances that reduce friction and seal imperfections in the various metals so that there is less friction. It is not some sort of "slick 50" kind of nonsense. Many name brand oils have some moly in them. healthy levels of moly that compliments a good dose of zinc, and you have what you need for some serious engine protection. Here is a set of 3 papers on Moly. Make sure you read the first two.

Moly Basics - Bob is the Oil Guy - Bob is the Oil Guy

And for a great source for information on selecting a good quality oil, try this on for size....

Conventional 5w30's. From what I have read elsewhere, the Pennz 5w30 would be your best choice. It is rich in Moly. It is held in very high regard by many folks with a lot more experience than any of us here put together, and several oil engineers and tribologists like the Pennzoil "Yellow Bottle" or PYB for short. It is a great value.

Petroleum Quality Intitute of America

If you are motivated to go with a synthetic, here is a side by side of a batch of them. The Kendall GT-1 is a killer choice. It doesn't have a large amount of moly, but it complements it with titanium which is a great combination. I use the Schaeffer 9000, but it is hard to locate retail for many folks. I get mine with my commercial oil supply from Schaeffer.

March 2013 - Test Results for AP