Depends upon how you drive. With lots of WOT the colder plug; mostly easy cruising the hotter plug.

 

Easy Vista Cruiser-ing for sure. Anyone else?

 

The colder plugs were used on the higher performance/compression engines. Consider using the spec'd plug unless doing a lot of short trips then go up one heat range, I wouldn't go up two heat ranges. Pull a few plugs after a few trips after reaching full temp and read them.

The 330 4BBL should be the high compression engine...correct...anybody???

Good luck!!!

 

4BBL is HC. So says the label on the air cleaner housing, too.

 

Didn't a red air cleaner housing signify an HC engine also?

 

 

I started using Autolites in all my Oldsmobiles since about 1985. Seem to last twice as long as any other plug. Its just a simple durable plug(was?). Though I haven't purchased a set since the MFs moved to china grrrrrr...so tired of china...

Cross ref is R43S = 87..........R42s = 73. I use the 87s

 

As mentioned, operational circumstances also mean something. I usually prefer the colder plug until too much deposit results; then move to warmer one.

 

The AC Delco and Autolite plugs aren't bad, supposedly made on the same line, just not as good as before.