Octane boost

[Daniel R]

Since we are on the fuel debate, is there any benefits to running leaded petrol? My understanding about the shift to unleaded is that lead additives are not compatible with catalytic converters. My car no longer has cats, so does this mean I can use leaded fuel?

In Australia 98 RON unleaded is readily available, and is all I use in the boxster. I'm just wondering if the lead would somehow help the motor apart from increasing octane. Maybe it lubricates better or something??

Your thoughts are much appreciated.

[eightsandaces]

I was always told leaded gas was bad for the catalytic converter, that's why they changed the nozzle at first too, so one couldn't make a mistake in the changeover years. The Fiat has a wide open 4" filler.

[Lil bastard]

Originally Posted by Daniel R

Since we are on the fuel debate, is there any benefits to running leaded petrol? My understanding about the shift to unleaded is that lead additives are not compatible with catalytic converters. My car no longer has cats, so does this mean I can use leaded fuel?

In Australia 98 RON unleaded is readily available, and is all I use in the boxster. I'm just wondering if the lead would somehow help the motor apart from increasing octane. Maybe it lubricates better or something??

Your thoughts are much appreciated.

The lead used in leaded gasolines was a form called tetra-ethyl Lead and was initially only used in Premium or High Octane gas, which commonly became known as Ethyl - some companies even marketed it under this name.

This additive raised the octane rating of the fuel inhibiting detonation and also helped lubricate and seal the valves whose seats were made of soft mild steel for better sealing. This is why valve adjustment on earlier cars was so frequent -= the valve would get pounded further and further into the seat - the lead acted similar to RTV on a gasket.

Because engines today are not designed to use it, and are machined to much closer tolerances using different materials (esp. the valve seats), and usually with a much lower CR, using leaded gas in today's engines would not likely yield the same benefits. Aside from damamging the cats (by coating the ceramic matrix with lead, thus reducing it's useful surface area to react with the exhaust), it would also make your O² sensor inoperable after only a few miles.

And, all of this is aside from the obvious environmental issues.

Cheers!

[stateofidleness]

I've been using THIS about every 3 fills and I notice a VERY nice difference in the way my car performs (and sounds smoother)

is this just as bad as the "octane boosters" or is this stuff safe to use?

[Daniel R]

Originally Posted by Lil bastard

The lead used in leaded gasolines was a form called tetra-ethyl Lead and was initially only used in Premium or High Octane gas, which commonly became known as Ethyl - some companies even marketed it under this name.

This additive raised the octane rating of the fuel inhibiting detonation and also helped lubricate and seal the valves whose seats were made of soft mild steel for better sealing. This is why valve adjustment on earlier cars was so frequent -= the valve would get pounded further and further into the seat - the lead acted similar to RTV on a gasket.

Because engines today are not designed to use it, and are machined to much closer tolerances using different materials (esp. the valve seats), and usually with a much lower CR, using leaded gas in today's engines would not likely yield the same benefits. Aside from damamging the cats (by coating the ceramic matrix with lead, thus reducing it's useful surface area to react with the exhaust), it would also make your O² sensor inoperable after only a few miles.

And, all of this is aside from the obvious environmental issues.

Cheers!

Thanks for the reply.

My question was more from an academic perspective, not that I am going to fill my car with leaded fuel just because I have removed the cats. I didn't even think about the O2 sensors though. So I was right that lead additives had other benefits, it is just that the modern motor renders these benefits useless. I'll stick with the 98 RON BP Ultimate. Thanks again.

Daniel