Eh?

[alex_antonin]

I don't get why gasoline ever had lead in it in the 1st place, that makes no sense at all. You don't put iron or nickel in kerosene, so why lead (of all the random things) in gasoline???

Comments

[kengr]

The "lead" in gasoline was tetraethyl lead. It prevented "knocking" (premature detonation of the fuel-air mixture)

Other ways of preventing it make the gasoline more expensive.

I believe you can still buy tetraethyl lead as a fuel additive for really old cars, as their engines won't run right without it.

[alex_antonin]

The "lead" in gasoline was tetraethyl lead. It prevented "knocking" (premature detonation of the fuel-air mixture)

Other ways of preventing it make the gasoline more expensive.

What, they can't come up with a mechanical solution to the problem??? Or, I dunno, switch everyone to diesel?

I believe you can still buy tetraethyl lead as a fuel additive for really old cars, as their engines won't run right without it.

That sounds fake. How would the engine even know the difference between the tetraethyl lead and whatever else they use?

[kengr]

There *is* no "mechanical solution". The "knocking" is a matter of temperature & pressure, plus the laws of chemistry.

The temp and pressure are part of how the engine runs. Change them and you change the performance of the engine (usually for the worse).

Diesel engines are built a lot different than gasoline engines. They don't have spark plugs, and they use *much* higher compression. and need high pressure fuel injectors to get the fuel/air mix into the cylinders.

They used to call gas with tetraethyl lead "ethyl" gasoline. It was cheaper but gave the same performance as the more expensive premium gas.

I think the bit with older cars needing the leaded gas has to do with the lead depositing on the pistons and cylinders and affecting wear (in a good way) or some such.

Oh yeah, in case you didn't know, back when they still sold leaded gas alongside unleaded, the nozzles were different sizes. you could put unleaded in any car (though it wasn't good for the oldest ones that were *designed* for leaded gas), but the nozzle for leaded gas wouldn't fit the fill tube for a car that was supposed to take unleaded.

Also, the lead would poison a catalytic converter. Which is expensive to replace (because of the platinum in them)

Likewise, using ethanol, or a gasoline ethanol mix in a car not set up for it can ruin the engine or at the least some parts of the fuel system. Part of that is that ethanol will dissolve some plastic that aren't affected by gasoline, and part of it is that you need a different fuel/air mix and cooling settings.

[alex_antonin]

There *is* no "mechanical solution". The "knocking" is a matter of temperature & pressure, plus the laws of chemistry.

The temp and pressure are part of how the engine runs. Change them and you change the performance of the engine (usually for the worse).

That could easily be solved by putting more effort into a higher quality engine. Thus again solving a chemistry problem with a mechanical solution.

Diesel engines are built a lot different than gasoline engines. They don't have spark plugs, and they use *much* higher compression. and need high pressure fuel injectors to get the fuel/air mix into the cylinders.

I already knew all that, learned it back in high school.

I think the bit with older cars needing the leaded gas has to do with the lead depositing on the pistons and cylinders and affecting wear (in a good way) or some such.

???

Oh yeah, in case you didn't know, back when they still sold leaded gas alongside unleaded, the nozzles were different sizes. you could put unleaded in any car (though it wasn't good for the oldest ones that were *designed* for leaded gas), but the nozzle for leaded gas wouldn't fit the fill tube for a car that was supposed to take unleaded.

Good design.

Also, the lead would poison a catalytic converter. Which is expensive to replace (because of the platinum in them)

Yup.

Likewise, using ethanol, or a gasoline ethanol mix in a car not set up for it can ruin the engine or at the least some parts of the fuel system. Part of that is that ethanol will dissolve some plastic that aren't affected by gasoline, and part of it is that you need a different fuel/air mix and cooling settings.

Ah.

[kengr]

There *is* no "mechanical solution". The "knocking" is a matter of temperature & pressure, plus the laws of chemistry.

The temp and pressure are part of how the engine runs. Change them and you change the performance of the engine (usually for the worse).

That could easily be solved by putting more effort into a higher quality engine. Thus again solving a chemistry problem with a mechanical solution.

It's not a matter of "quality". It's that to get a given level of performance, you need certain pressures in the engine. And the lower "quality" fuel knocks under those conditions. So the lead was an additive that let you use cheaper fuel without the engine knocking.

Without the lead, the engine won't run right on that fuel, nor will it perform up to par (in fact, as I recall, knocking bad for the engine).

An engine that will run on the lower "quality" fuel won't have as high a performance/power.

Ah! Got it. The lead raises the pressure at which the fuel ignites. That lets the engine achieve the pressure (and piston position!) required to run properly.

Knocking ("pre-detonation") has the fuel igniting while the piston is still on the upstroke. So it's fighting crankshaft because it's not yet to the point where the explosion will drive it in the proper direction.