# Spark Plug Discrepancy **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [May 27, 2014, 6:12pm UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193 "2014-05-27T18:12:21Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![jmcarc](https://avatars.discourse-cdn.com/v4/letter/j/278dde/32.png) [@jmcarc](https://community.cartalk.com/u/jmcarc)\ **Post date:** [May 27, 2014, 6:12pm UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193/1 "2014-05-27T18:12:21Z")
I have a 1992 Buick Century with a 3.3L V6. The spark plug specified in my owner’s manual is AC Delco R45LTS-6. When I researched this part number on the Autozone Store website, I received the warning “This part DOES NOT FIT your vehicle”. Instead, Autozone recommends AC Delco 41-601. I compared the specifications for both plugs and found two minor differences. The original plug has a ribbed insulator and a 2-12-220 resistor (don’t know what this number means). The plug that Autzone recommends has a smooth insulator and a 2.5-12-220 resistor. Can anyone explain this discrepancy? Were there changes in environmental laws that changed the correct plug type? ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [May 27, 2014, 6:38pm UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193/2 "2014-05-27T18:38:43Z")
The AC Delco site agrees with the Autozone site. I guess the R45LTS-6 is obsolete. ---
**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\ **Post date:** [May 27, 2014, 7:09pm UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193/3 "2014-05-27T19:09:48Z")
I believe that the part’s numbering format was changed. The earlier number was quite descriptive compared to the newer part’s numbers. As I recall the R meant resister, the 45 was the heat range, L had extended tip, TS was tapered seat and the 6 meant pre gapped to .060. But my memory, like my good looks, isn’t what it used to be. ---
**Author:** ![jmcarc](https://avatars.discourse-cdn.com/v4/letter/j/278dde/32.png) [@jmcarc](https://community.cartalk.com/u/jmcarc)\ **Post date:** [May 27, 2014, 8:10pm UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193/4 "2014-05-27T20:10:23Z")
I forgot to ask another question. Should I replace the plugs when the engine is cold or a little warm? ---
**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\ **Post date:** [May 27, 2014, 11:11pm UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193/5 "2014-05-27T23:11:10Z")
I believe it’s preferable to let the engine cool down enough that you can touch it. ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [May 27, 2014, 11:40pm UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193/6 "2014-05-27T23:40:56Z")
Cold…especially with an Aluminum head. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [May 28, 2014, 3:56am UTC](https://community.cartalk.com/t/spark-plug-discrepancy/85193/7 "2014-05-28T03:56:39Z")
Straight from the horse’s mouth [http://parts-catalog.acdelco.com/catalog/catalog\_search.php](http://parts-catalog.acdelco.com/catalog/catalog_search.php) I also agree with the others . . . go with the 41-601 [Rockauto.com](http://Rockauto.com) says this is the conventional plug for you [http://www.rockauto.com/catalog/moreinfo.php?pk=89995&cc=1015973](http://www.rockauto.com/catalog/moreinfo.php?pk=89995&cc=1015973)