# Api sl..sm?

**URL:** <https://community.cartalk.com/t/api-sl-sm/52766>\
**Category:** Maintenance/Repairs\
**Tags:** toyota, tundra\
**Created:** [July 31, 2010, 6:58pm UTC](https://community.cartalk.com/t/api-sl-sm/52766 "2010-07-31T18:58:53Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Joe-Guy](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joe-guy/32/124_2.png) [@Joe-Guy](https://community.cartalk.com/u/Joe-Guy)\
**Post date:** [July 31, 2010, 6:58pm UTC](https://community.cartalk.com/t/api-sl-sm/52766/1 "2010-07-31T18:58:53Z")

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At this moment I’m changing the oil in my 2002 Toyota Tundra. While re-filling with fresh oil that I bought yesterday (Toyota API SL, SAE 5W-30) I grabbed an half-filled quart from the shelf from when I changed the oil about 7 months ago. The label on the bottle says "API SL, SAE 5W-30.  
  
  
  
 So what’s the difference between SL and SM?  
  
  
  
 Will the next oil I buy be SN?  
  
  
  
 Just curious

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**Author:** ![Joe-Guy](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joe-guy/32/124_2.png) [@Joe-Guy](https://community.cartalk.com/u/Joe-Guy)\
**Post date:** [July 31, 2010, 7:01pm UTC](https://community.cartalk.com/t/api-sl-sm/52766/2 "2010-07-31T19:01:16Z")

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Correction! I meant to write that I’m currently filling with API SM, SAE 5W-30.

Is there a way to edit posts?

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**Author:** ![PvtPublic](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/pvtpublic/32/13089_2.png) [@PvtPublic](https://community.cartalk.com/u/PvtPublic)\
**Post date:** [July 31, 2010, 7:24pm UTC](https://community.cartalk.com/t/api-sl-sm/52766/3 "2010-07-31T19:24:41Z")

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It is a rating system From the American Petroleum Institute. The Second letter “L,M” and yes probably soon “N” service categories. The First letter “S” is for gasoline, spark ignition engine the other is “C” for diesel compression ignitions. You can get a much better explanation than I can give at:  
[http://www.api.org/certifications/engineoil/categories/index.cfm](http://www.api.org/certifications/engineoil/categories/index.cfm)

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<div class="post-metadata">

**Author:** ![Joe-Guy](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joe-guy/32/124_2.png) [@Joe-Guy](https://community.cartalk.com/u/Joe-Guy)\
**Post date:** [July 31, 2010, 7:32pm UTC](https://community.cartalk.com/t/api-sl-sm/52766/4 "2010-07-31T19:32:15Z")

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Thanks for the link!

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**Author:** ![geeaea](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@geeaea](https://community.cartalk.com/u/geeaea)\
**Post date:** [August 1, 2010, 2:51am UTC](https://community.cartalk.com/t/api-sl-sm/52766/5 "2010-08-01T02:51:09Z")

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Essentially the difference is the phosphorus and zinc levels. SL had higher allowances.

Phosphorus is poisonous to your catalytic converter. It’s a policy thing. You can be processing more phosphorous through your engine (having some percentage volatilizing and poisoning your cat) by changing SM too often. It’s a policy thing since if you’re changing it too often, you’re poisoning it less than you were at higher additive levels.