Classic/Antique Car Repair: The Reason Behind The 20w-50 Oil, shell rotella, ford mustang

Question
QUESTION: Hi Brad

I'm not a car guy but I'm learnin' as much as I can being a 71yr. young ol' man . . . lol

Seriously Brad. I went to AutoZone and got my 20w-50 oil & new oil filter.
The gal behind the counter told me that before I install my
new oil; fill the filter up about half way before I install it.

She started to tell me why and for some reason this old brain of mine shut-off. I don't remember what she said ?

Brad is that true and WHY should I do that ?

Thanks Brad
GOD BLESS YOU
Ray M. :-)

ANSWER: Well Ray from one old guy to another, good morning. However you are still a youngster as I am pushing 80, still working on cars, and have no plan to retire. Now to the filter. It is a good idea to pre load the filter with oil if the filter mounts straight up and down. But is the filter is mounted horizontally just smear a little oil on the gasket and spin it on by hand. Loading the filter with oil just means that oil pressure will come up a little faster when you start the engine. Now I did notice the use of the 20W-50 oil and wonder why the heavy oil? these new engines are made to run on 5W-30. The oil clearances on the newer engines are so close that using the thicker oil is not recommended. It can make a difference in fuel economy. My 1994 Ford Explorer work truck with 300,000 miles on the clock still uses 5W-30. It burns a quart of oil in 1,000 miles. However my Benz diesel with only 200,000 miles uses 15W-40 Shell Rotella. Good luck, Brad

---------- FOLLOW-UP ----------

QUESTION: Hey Brad

Thank you 4 filling me in on why I should fill my new oil filter half-way.
I'll rate you after your answer my reply to: 20W-50 oil I'm going to use.

My 1966 Ford Mustang Convert. has the original block. However, it was bored-out 30ths. with fuel injections.

I live in Las Vegas and as you don't know it doesn't get hot here IT GETS "BURNING"
Brad like I said before I'm not a car guys but I'm learning all the time.

I do hope that I'm doing the right thing by going to use the 20-50 oil ?
GOD BLESS YOU BRAD
71yr. young Ray M. :-)

Answer
Good morning:
With unknown history on the engine rebuild and the temperatures that you see out there, I think that the 20W-50 oil will work in your car just fine. The 5W-30 oils work well in the factory mass produced engines that we see today. A lot of the performance engine builders when doing an engine and doing an overbore will make the rod and main bearings a little looser than factory specs. In this case the heavier oil is recommended. And as I said, not knowing  what was done, lets err on the side of safety and use the heavier oil. Stay well friend.
Brad