Tune up label on my car calls for a AC Delco R46S spark plug for my 72 CS 350 auto trans. However what are other options and why. What is a R45S compared to the R46S. What the heck are all those letters mean? Are Champion or NGK a good option? I just drive the car as a daily runner some small hiway trips of under 120 miles.

 

Just get the R46S, they will work fine.

 

r45s is a one step colder plug, I have used both Champion and NGK plugs, both are good plus
the breakdown of the plug
R designates a resistor plug
'4 is the thread size 14mm
'5 is the heat range
'S means extended tip....

Attached is a good decoder I found on the internet
http://toms427impala.info/CT/ACPlugInfo.pdf

 

You asked a good question. The numbers have meaning. Review the following for a basic understanding of the meanings behind spark plug numbering from Champion.

https://www.championautoparts.com/Te...ark-plugs.html

If you're so inclined, you can perform a cross-reference on nearly any spark plug manufacturer.

http://www.angelfire.com/extreme4/sk..._REFERENCE.htm

 

Your other questions have been answered, so for this one, yes, those are acceptable alternatives for the AC Delco plug. I have used Champion RJ12YC plugs in my Olds engine since around 1980.

 

Sorry, I was mistaken on this suggestion and for some reason thought it was the R45S that was discontinued. You can use the R45S in its place.

 

The NGK XR45 or XR5, one step colder are both good choices for Olds V8's.