STILL CONFUSED ABOUT MOTOR OIL

[Arizona Mike]

I need to do an oil change now on two Cubs that I’ve only had a few weeks. Both have always been run on Case IH Low Ash 30wt. motor oil. Both engines are original and not rebuilt. Both run good with a little valve clatter in one. Neither one smokes.

I talked to Gene D. and others about this at Farmer's Cubfest. Gene, who has excellent knowledge about lubricants, says that changing to modern high detergent oil would be beneficial, and clean up the engine of sludge. Some have said high detergent oil will weaken the seals and lead to an oil leak...others have said that modern oil will feed the seals and make them better.

Please tell me your thoughts and your recommended motor oil for these two.

Is anyone using synthetic?

Mike

[Pete]

Mike --

I am new to Cubs but have some experience with Ford N series wheel tractors and Caterpillar track tractors. Anyhow, my thoughts on lubricants are that a non-detergent oil should be used when lubricating a non-filtered engine. ND oils will allow particulate matter to settle out in the pan thereby keeping them out of the bearings, etc. ND oils should also be used if an old filtered engine has been run on them for a considerable amount of time. This is because the engine will likely have significant sludge buildup which will be losened by the introduction of a detergent oil and may plug passages.

Detergent oils are designed to hold particulates in suspension so that they are carried to the filter to be removed. Therefore they should be used whenever possible in filtered engines such as the Cub's. Modern detergent additives are essentially soaps of a sort and will not adversely affect neoprene, cork, leather, polyethylene, polypropylene or most anything else that seals are made of. That said, however, if one has a seal which is questionable and is kept from leaking by some deposits around the seal then a detergent oil will cause such a seal to leak, but not because of damage to the seal. The seal was already shot, the oil just cleaned things up so that the damage was evident.

Of course, this assumes all else equal such as viscosity, API service and base. In a nutshell, I use detergent oil in all my newly rebuilt engines except non-filtered ones and I use whatever has been used previoulsy in engines which are likely to be sludgy. So far so good. Whichever one chooses, Detergent or ND, I think the choice of base oil and viscosity are far more important to engine longevity.

Respectfully,

Pete P.