# Another 2 cycle/stroke oil question **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [October 29, 2009, 12:47pm UTC](https://community.cartalk.com/t/another-2-cycle-stroke-oil-question/38763 "2009-10-29T12:47:14Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![grampy](https://avatars.discourse-cdn.com/v4/letter/g/a9adbd/32.png) [@grampy](https://community.cartalk.com/u/grampy)\ **Post date:** [October 29, 2009, 12:47pm UTC](https://community.cartalk.com/t/another-2-cycle-stroke-oil-question/38763/1 "2009-10-29T12:47:14Z")
I have been in the habit of dumping old 2 cycle oil mix in my car gas tank in small amounts. I recently was informed by a mechanic to not do this as,even small amounts can ruin the Catalytic converter. Thoughts? ---
**Author:** ![Manolito](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/manolito/32/3070_2.png) [@Manolito](https://community.cartalk.com/u/Manolito)\ **Post date:** [October 29, 2009, 2:11pm UTC](https://community.cartalk.com/t/another-2-cycle-stroke-oil-question/38763/2 "2009-10-29T14:11:35Z")
An interesting question that I think only a chemist who makes 2-stroke oil will be able to resolve. I would have dumped it in my gas tank without thinking twice. 2-stroke oil is made to burn without ash, so I would not have expected residue to accumulate on catalyst surfaces. However, it may have lubricity enhancers blended in at parts-per-million levels. These compounds will not need to be listed on the material safety data sheet because they are not there at high enough concentrations to be reportable. I can think of compounds that might be used that would not be good for oxygen sensors and catalytic converters. Your mechanic may be correct. Just to be safe, I guess that if I find myself with 2-stroke oil to get rid of, I will burn it in my old 4-stroke lawn mower, not in my car. ---
**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\ **Post date:** [October 29, 2009, 4:29pm UTC](https://community.cartalk.com/t/another-2-cycle-stroke-oil-question/38763/3 "2009-10-29T16:29:40Z")
A little bit at the time added to a full tank of gas will do no harm. 4 stroke cycle oil does not have near the additives in it that regular motor oil has (up to 28%). The oil in the gas will burn just like crankcase oil coming up past the rings will. The secret is small doses. What do I do with my leftover gas/oil mixture? It goes to the landfill where they have a special tank for old gasoline and diesel fuel. It gets recycled at a nearby plant. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [October 29, 2009, 5:14pm UTC](https://community.cartalk.com/t/another-2-cycle-stroke-oil-question/38763/4 "2009-10-29T17:14:36Z")
One of the properties of 2-stroke oil is that it burns VERY cleanly. I have dumped 3 gallons of mix, which contained a half-pint of outboard oil, in a 20 gallon automotive fuel tank. The dilution ratio is now insignificant and will not harm the converter or anything else…They still sell “top-oil” which is virtually the same thing and it does no harm… ---
**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:** [October 29, 2009, 5:20pm UTC](https://community.cartalk.com/t/another-2-cycle-stroke-oil-question/38763/5 "2009-10-29T17:20:40Z")
If you figure 1 quart of oil per 1000 miles is OK for a car to burn (according to most carmakers), and assume 20 mpgs, that’s 1 quart/50 gallons. Keep it under that amount, I don’t see where it would do harm (ignoring any wierd chemical additives, that is).