As far as the lead substitute goes, you only need that if you still have the original style valve seats, if the engine has been rebuilt in the last decade or so it will probably have hardened seats and doesn't need the additive.

 

Octane has a hell of a lot more to do with things than just the engine's compression. And there can be substantial differences between fuels of differing octane due to blending and refining. A higher octane fuel is NOT the same fuel with more detonation resistance. If a higher octane fuel has a lower vaporization point, and a higher volume % vaporized at a given temperature, then it's going to vaporize, and as a result, combust more completely and rapidly. A higher octane fuel does not necessarily burn more slowly. They may also have differing specific gravities, and if the SG is higher on a higher octane fuel, then there's more fuel molecules, and therefore energy, in a given volume. That means that you don't have to burn as much fuel volume to release the same energy, and you get better mileage.

It really depends on the nature of the specific fuel. There are high octane fuels out there that will get better mileage and make more power on the same tune than lower octane fuels. Plus they're more refined and have less crap in them.

 

Simply put, it's the fuel/air mixture exploding before the piston completes it's stroke and the sparkplug fires. All havoc ensues.

 

Thats when the fuel burns in your chamber

 

Every car reacts differently to economy and premium. Oddly enough some car don't see any gains between the two. It's not abortion people so don't get your panties in a bunch. As Nabner said above if you've been rebuilt in the last 15 years or so you should be good to run unleaded. I ran premium in my old all original 65 because I didn't know any different and it ran fine.

 

Roger that. Good sight picture - one shot, one kill!

 

My car definitely runs smoother on 91 (the highest octane in CA) but I now realize that since I have hardened valve seats, lead sub is a waste of five dollars. Thanks, Nabster.

True66 also has a good point. Money saved on gas mileage or cost per gallon shouldn't be an issue if we drive these cars. The difference that you spend in octane in one year is less dough than you would spend buying drinks for some mini skirt in one night, and you might not have detonation, even after fueling her up with 3 Cosmos.

CP

 

On the bright side, the lead sub doesn't hurt the engine, if it makes you feel better you can still add a bottle every once in a while Probably more fun to take the extra $5 a fillup and get better gas though.

 

Will it hurt an original engine to run it without the lead sub?

 

Eventually the valve seats will be basically eaten away and you'll end up with a major problem. The trouble is, in this circumstance "eventually" is different for every engine, some have no problems and others go fairly quickly.