The Stovebolt Site Forums The Shop Area Engine Shop OIL?

I've been running straight weight SAE30 in my rebuilt 350, as I was told to do to break in the cam. Does this agree convention? Also, I figure I oughtta call it quits with this before real cold weather & go to 10W-30. Is that what you guys run in the wintertime? FEEDBACK PLEASE!!!

Bluto,

This type of question usually brings forth a multitude of theories. My theory would be, from a "cam concern" standpoint, it isn't the viscosity that is critical, but the extreme pressure additives, IE, zinc, and actual break-in procedure.

The levels of this additive have been drastically reduced in the API oils marked for gas engine service (S prefix). Unless a aftermarket additive was added to the oil to address this concern, cam lobe and lifter failure COULD be an issue.

Many of the motor oils marked for commercial, or diesel engine use (API D-prefix) still have zinc. This additive, along with a cam manufacturers break-in procedure will be the critical issue.

I think the rings would be happy with any oil, and 10/30 is certainly a popular multi-grade for your engine, cold weather or otherwise.

So, to get net...generally speaking, cam break-in concerns don't have lots to do with oil viscosity as opposed to oil type (additives), aftermarket additives, and actual immediate break-in procedure.

Your engine is probably running find right now, so switch to any old oil you want, or can afford. Synthetics are pretty nice too.


Stuart

Any oil with the SL rating (in the circle on the bottle) should be OK but it's getting hard to find SL oil. Even Rotella (I checked every store in town) is showing the SM rating which indicates no/reduced zinc, the reduction of which has been linked to cam wear. From what I've read the zinc is plugging up catalytic converters so it's being fazed out. I've also read that the oil companies realize that they are making life hard for us old car nuts and are in the process of coming out with lines of oil with zinc for classic cars. I wasn't able to find any locally though. I was finally able to find enough "Costal" SL oil to change the oil in my 38. I'll probably end up having to buy some additive next time. Most folks here seem to be succussfully using multi-viscosity oil from the posts I've read so some 10W30 SL (if you can find it) should do you OK for any season.