F-85 4-4-2

Fun71

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

F-85 4-4-2

Easy Vista Cruiser-ing for sure. Anyone else?

Sugar Bear

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!!!

F-85 4-4-2

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

TripDeuces

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

F-85 4-4-2

droldsmorland

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

Ozzie

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

olds 307 and 403

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