# Old Hot Rods/show cars with leaded gas and todays gas **URL:** \ **Category:** Factual Questions\ **Created:** [September 7, 2001, 5:47pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269 "2001-09-07T17:47:08Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Shirley\_Ujest](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shirley\_Ujest](https://boards.straightdope.com/u/Shirley_Ujest)\ **Post date:** [September 7, 2001, 5:47pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/1 "2001-09-07T17:47:08Z")
Driving behind a hot rod (circa 1930’s) recently, I was wondering about older cars that ran on leaded gas and what kind of fuel they use now since everything is unleaded. Can you still buy leaded gas anywhere? Do they use some kind of converter? Just put a new engine in ? Or do they just use unleaded gas and deal with engine knock and poor performance? ---
**Author:** ![MIKE\_P](https://avatars.discourse-cdn.com/v4/letter/m/ba9def/32.png) [@MIKE\_P](https://boards.straightdope.com/u/MIKE_P)\ **Post date:** [September 7, 2001, 5:53pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/2 "2001-09-07T17:53:47Z")
Well,some old cars can run on premium unleaded,but some will require a fuel additive that add more octane. Some hotrods are rebuilt with lower compression ratios,so they can run on unleaded. I dont think leadded gas can be found in the U.S. ,but it can be found in Europe. ---
**Author:** ![Von\_Erich](https://avatars.discourse-cdn.com/v4/letter/v/d78d45/32.png) [@Von\_Erich](https://boards.straightdope.com/u/Von_Erich)\ **Post date:** [September 7, 2001, 5:54pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/3 "2001-09-07T17:54:26Z")
they use a lead additive you can buy at most auto parts stores and some gas stations. You just pour it into your tank every time you fill up. ---
**Author:** ![Reeder](https://avatars.discourse-cdn.com/v4/letter/r/c6cbf5/32.png) [@Reeder](https://boards.straightdope.com/u/Reeder)\ **Post date:** [September 7, 2001, 5:57pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/4 "2001-09-07T17:57:23Z")
They sell a lead substitute that you can add to the gas. [http://www.autobarn.net/chm50-12.html](http://www.autobarn.net/chm50-12.html) ---
**Author:** ![Shirley\_Ujest](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shirley\_Ujest](https://boards.straightdope.com/u/Shirley_Ujest)\ **Post date:** [September 7, 2001, 5:59pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/5 "2001-09-07T17:59:32Z")
Wow. I love you dopers. Taking the mystery out instantly. My next brain melting question is: what happened to my waistline and where did it disappear to 🙂 Mucho gracias. ---
**Author:** ![Tedster](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@Tedster](https://boards.straightdope.com/u/Tedster)\ **Post date:** [September 7, 2001, 6:26pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/6 "2001-09-07T18:26:48Z")
Lead was the most practical/cheapest method of raising the octane of fuel, it also provides lubrication for the upper cylinder area, particularly valves/valve seats. High compression engines require a fairly high octane fuel, it can still be sometimes obtained at airports (100 LL or “low lead”) although expensive. Supposedly running lead free in older engines will not harm them at low engine revolutions or speeds. But, any highway type use will dramatically wear the valve seats down. Typical engine rebuilding practice today is to install hardened valve seats, rendering the use of lead free gasoline pretty much of a non-issue from that standpoint. ---
**Author:** ![Blown\_Injected](https://avatars.discourse-cdn.com/v4/letter/b/a87d85/32.png) [@Blown\_Injected](https://boards.straightdope.com/u/Blown_Injected)\ **Post date:** [September 8, 2001, 6:30am UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/7 "2001-09-08T06:30:15Z")
Tedster nailed it. Most race fuel is leaded and available at the track for $4 - $6/gallon ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [September 8, 2001, 3:17pm UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/8 "2001-09-08T15:17:26Z")
Lest anyone get the wrong idea, we’re not talking about adding pure lead to gasoline. The additive is a compound called tetraethyl lead, Pb(C[sub]2[/sub]H[sub]5[/sub])[sub]4[/sub] ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [September 9, 2001, 1:03am UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/9 "2001-09-09T01:03:35Z")
Leaded gas $4-$6 at the track? 100LL was only $2.35/gallon last time I tanked up the plane at the airport, and should be available at just about any airport that sells gas since it’s what most small, single-engine planes use. Then again, there could be significant differences between avgas and racing gas I don’t know about. Mechanics have told me that if you put unleaded in an engine designed for leaded you will increase engine wear and shorten the life of the cylinders. It’s not just a matter of octane but the lead compound also providing some lubrication. ---
**Author:** ![mojo\_filter](https://avatars.discourse-cdn.com/v4/letter/m/b5a626/32.png) [@mojo\_filter](https://boards.straightdope.com/u/mojo_filter)\ **Post date:** [September 10, 2001, 4:31am UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/10 "2001-09-10T04:31:28Z")
I hope noone is forgetting the valve guides. The lead in the fuel is the only lubricant these guys will see and if they are not of the unleaded/hardened variety they will not last long at all. ---
**Author:** ![Blown\_Injected](https://avatars.discourse-cdn.com/v4/letter/b/a87d85/32.png) [@Blown\_Injected](https://boards.straightdope.com/u/Blown_Injected)\ **Post date:** [September 11, 2001, 4:02am UTC](https://boards.straightdope.com/t/old-hot-rods-show-cars-with-leaded-gas-and-todays-gas/80269/11 "2001-09-11T04:02:54Z")
More important, or perhaps relevant for most engines on the road today - if ya put leaded in a modern car, the O2 sensor will die or get extermrly lazy before the tank is finished and it will not do the catalytic converter much good either. I’ve read that the low lead avgas has about as much lead as the race fuel. While there are several big differences in race fuel and avgas, people I know that have used both types of fuel have not noticed a difference. Of course if one is blowing 25PSI or more boost into thier grocery getter, race fuel can be found as high as 116 motor octane 🙂