1962 305d model 3000 What Oil Too Use

[Schroer1962v3000Dump]

New Member; New Old Truck; I recently purchased and have been rebuilding and using a 1962 v6 305d model 3000 12' stacked bed with dual cylinder Dump.... Completely original untouched except by Mother Nature. Im not for sure what Oil I should be using in the Motor I have tried 5w 20 synthetic for a motor flush maybe an hour of idle time then changed to 10w 40 currently in use. I have replaced all the wood flooring and runners with pressure treated yellow wood. Greased and replaced all fluids on entire truck. Runs and Drives great Dumps with ease but after 30 min or so she starts to smoke im guessing passed the rings but it doesn't effect the truck still idles at 500 rpm??? Also I replaced All the brake pads and rebuilt the front wheel cylinders. I replace the back brake pads but the wheel cylinder kits where wrong so they still Leak. Anyone know where I can get the correct rear wheel cylinder kit?
Thanks for any help you can give

[66birdman]

The oil thing is all about personal preference to an extent. The owners manual called for no heavier than 20 weight back in the day but that was before multiple weight oils came along. I normally use 10w30 in both my Tbird and my GMC just to make it easier to buy in bulk. If you are going to be driving it in any kind of extreme cold I would go with a little lighter oil than 10w40 for the colder months. My old PowerStroke called for 15w40 but during the NoDak winters I had to switch to 5w20 to get it to start in the morning even when it was plugged in.

[705jmguy]

hi, just rebuilt my 305 D and will be using Shell T5 semi synthetic 5 -30 weight , my reasoning it would be best of both worlds, does not go real thin with heat, and gives good flow when cold
do not use my truck in winter

[Schroer1962v3000Dump]

Thanks for the info Im thinking going with a royal purple syn 10/30

[Clyde]

I use Shell Rotella straight 30wt, that is what these engines were designed around. In 1964 I had a brand new 1964 GMC 3/4T pickup I put 100,000 miles on it in two years, running up and down the East Coast with my Top Fuel Dragster I had an 8 foot aluminum camper and an custom enclosed trailer for the car. The truck never missed a beat.

[66birdman]

Royal Purple is some great stuff for a race car or other performance vehicle. Anything else and you are wasting hard earned cash that could be spent elsewhere. Unless you are using that truck to tow across country I suggest against it.

[Schroer1962v3000Dump]

I wasn't planning to tow across country but I have several loads of rock to haul 5 to 7 tons at a time. I have already made a dozen or more trips on the farm with 3 tons or more for testing and looking for weak spots in trucks operating system.
I did place a call to a local lab "that I send my tractors used oils into for testing" to see what grade motor oil would be comparable to the original oil the motor was engineered for. You are right the most expensive usually isn't always the best but I'm on my third oil change in a month and sending this one in to check for bearing and block wear .