Hi, The old 194 in my 64 Chevelle was well worn, leaky, a little smokey, and generally tired. In an attempt to prolong it's stay in the car I tried twice to change from 10W40 to 20W50 Castrol (original GTX) Both times the valve train seemed to go nuts, clacking noises from seemingly all the lifters and valves. Dumping the oil and going back to the 10W40 would fix it. I never really understood what the problem was.
Couldn't be collapsed lifters? Lifters pumped up and stuck? Anyone have an idea on what was going wrong?
While the bottom end ( rings, bearings) can be loose with wear. And also the valve guides/ non existent seals. The lifters are very precise and do not wear much. Those tight tolerances probably do not want to pass thru that thick oil to the upper valve train thru the lifters. Maybe try a 5w40 syn. Beware, it may leak more than conventional oil.
Inliner Member 1716 65 Chevelle Wagon and 41 Hudson Pickup Information and parts www.12bolt.com
I tried a similar thing in my 1991 Jeep with 4.0. It has just over 200k and I wanted to run a little thicker oil in it. I went with Rotella 15w40 and it didn't like it. I have ran 10w30 and 10w40 with no problems, but it does not like the 15w40. I just wanted something thicker for the bottom end, the valve train is fine.
When the motor is up to temperature, only the number after the W matters
I have always found discussions about motor oils spirited - yet at the same time plagued with misconceptions - especially with regard to hobbyist engines where the benefits of multi-grades and "long life" oil change intervals are largely irrelevant.
Is a 10 weight base stock fortified with 40 weight Viscosity Modifiers the same as straight 40?
Is a 15 weight base stock fortified with 40 weight Viscosity Modifiers the same as straight 40?
The multi-viscosity grades were created to allow for flow at freezing and even subzero temperature winter starts.
What hobby car is being pressed into service on a -10F morning to go to the office/shop?
In my mind Viscosity Modifiers are simply a compromise for winter driving - without the need to change out the crankcase contents. Absent the need for cold starts - base 20W, 30W or 40W (without modifiers) is the best choice for certain antique engines.