oil for flathead?

I'm about to change the oil in my '49 with the flathead 6. Glove box door says 20W. What do you guys use?

Also is the canister filter reuseable?

 

No the filter inside the canister is replaced with a new elament.If i stayed with a single weight oil i would use 30W but 15w40 works too.I have been runing 20w50 in my flatheads.NAPA or any good parts house should cary the filter element.If you still have the oil bath air cleaner on it service it also.

 

I use 10-30 castrol.The filter inside the canister is NOT reuseable. Fram C4. Glenn

 

20/50W during the hot season I run kendal 50W

 

I Use the cheapest 15-40 oil i can get.
All oil today is (must be much) better than the oil back in the good old days.
No Oilfilter.

So i change every 300 mil = around 2000 miles.

 

I run 20/50w in my flathead all the time. It's always the hot season here in Phoenix.

And yes, replace the element in the cannister oil filter.

 

so no problems with newer oils and the fiber timing gears?

 

Use a 20w-50.

 

I have always run no heavier than 30 wt.(Cali) Why is the popular peoples choice 40 + wt. ?? Glenn

 

I've been told to use 20w-50 because of its flexibility. This oil behaves like a 20 wt oil at strart up but can behave like a 50w when needed. It helps with the flatheads notoriously low oil pressure and can withstand much abuse since most 20w-50 is a common racing blend.

 

15W40 is a great universal oil with a high detergent content... I run it in all my older cars, it's thin enough to pump fast on a cold start, thick enough for larger clearances, and heavy duty enough to see abuse. I usually go for PZ Long Life. There's no reason to use a single weight oil anymore, IMHO.