ZDDP/zinc additives for newer motor oil?

[aeroron]

I use sae 15w-40 weight in both my '79 Scout IH 345 I recently rebuilt and also in my old '79 Scout (250,000 mile) 345. Oil pressure is fine in both, although the older one uses a little oil over time. I used to live in Pennsylvania until 12 years ago and they were my daily drivers. Here in georgia I usually drive them mostly during warmer months, but they still get exercise all year from 30 to 90 degrees. So 15w-40 swepco or any quality brand that is good for solid lifter cams (similar to the old api class se) should be fine. Otherwise, I defer to the swepco agent in this forum.
Fyi: --I have the original '79 Scout owner's manuals and in the '79 owner's emissions manual it has a whole lot of choices of straight and multi viscosities for a whole range of air temperatures from -10f to +120f deg. Using from 5w-20 up to 20w-40 (with a service classification of se-cd, se, or cc).
--I also have the original '72 Scout owner's manual that says use sae 30 or sae 20w-40 for over 32deg. Air temp (with a service classification of sc or sd), and gives lower weights for lower temps.

 

[DF Sales&Marketing]

hey guys,
a lot of great info here but I didn't see anything on why you run certain grades of the stuff (10w30, 15w40 and 20w50).

So what grade of swepco would you recommend for my Scout?

It's a '77 with a 304, 727, 33 mtrs and 3.73s. I live in massachusetts where average temp might be 80 degrees when I use it in the summer and right around sea level. It is a summer truck only and does little to no towing (5k boat twice a year for about 40 miles total). I run it on the highway quite a bit tacking around 2900 rpm and I do maybe 4k miles a year.
Thanks,

The proper weight selection for engine oil is based primarily on the ambient temperature range the vehicle is operated in. Obviously, you would not want to run a high viscosity weight oil, like 20w50 in below zero temperatures. But for the location you mentioned I believe that the 15w40 will be a very good choice. Optimum ambient temperature range for 15w40 would be very close to 10 degrees f to 114 degrees f. If you wish to have a lower temperature flow rate you could drop down to 10w30, but it also drops the top end down slightly as well...somewhere around 105. On the other hand using a 20w50 will raise the bottom end temperature into an oil suitable for around 20, to a top end of 120 or so.

Ideally, the right weight choice would be to take into consideration the elimination of seasonal oil changes.

Hope that helps.