They don't "need" lead any more than pre-70s cars "need" lead. They were designed to run on leaded fuel, but there are lead replacement additives which are able to fulfill the same technical requirements. TEL is just cheap, effective, and well understood for legacy applications. It isn't the only option to boost octane, by far.
The only issue I had on my 240z was the valve seats were some super soft brass like material, those needed to be swapped as they were beat to up and did not seal. The 75+ heads, all have steel seats.
I’ve actually never experienced the, “California gas sucks” issue that car people from the mid-west talk about, have never had an issue with it. ¯\_(ツ)_/¯
Maybe my understanding is incomplete, but AFAIK the "California gas sucks" thing is just because the highest grade you can find at most pumps there is 91, while we get 93 in a lot of other states
Not that it matters when everything made for "premium" is tuned for 91 from the factory anyway, not 93
California actually has different gas that produces fewer emissions - it's part of the reason gas is more expensive here. It's called CARBOB grade, c.f. RBOB/CBOB.
They are, however, manuals and documentation for US market vehicles will be specified in AKI (aka '(R+M)/2') regardless of who manufactured them. Some manuals also specify both AKI and RON, and that can be a source of confusion.
I'm in Europe and here it would be "98 recommended, 95 allowed with possible degradation in performance", as it's the case for my 2006 car. More modern small volume turbocharged engines should be even more sensitive to octane number due to higher compression ratios than common American engines of twice the volume for the same horsepower. The engine ECU will reduce boost pressure and fuel charge based on feedback from the knock sensor.
California 'gas sucks' for a couple reasons which are easy to miss if you're in California.
1) Few refineries make it, so it's MUCH more expensive. But if you're living in California, it is easy to miss because EVERYTHING is much more expensive.
2) Mileage is generally poorer, due to the mandatory ethanol mixes. But some places also usually mix in ethanol, and the difference is usually in the 10-15% range. So unless you have a good A/B comparison going, it's also easy for it to blend in with all the stop and go driving, and terrible road conditions.
3) Mandatory Ethanol means generally very poor storage characteristics. Which considering how much driving happens in California (and how dry the climate is in the populated areas), most people won't notice.
So does it suck? Comparatively, definitely! Is it likely to be noticed unless you're very aware and have experience with other options? Nope.
I understand that additionally in some vehicles (not necessarily aircraft) predating ethanol dilution the evap systems may begin to malfunction at high elevation and temperature due to the lower initial boiling point of ethanol.
In the case of my vehicle it results in low/rough idle and positive fuel tank pressure which otherwise do not occur either at lower elevation or with ethanol-free fuel at elevation.
Once you've replaced those valve seats with hardened ones, you don't have to worry about adding lead substitute in every fill up. You do still have to worry about getting the right oil additives though, as the old flat tappet engines need more zinc than modern oil blends have in them. Ethanol in the gas is also a concern, but any conscientious classic car owner has hopefully replaced all the rubber and plastic bits in the fuel system to ethanol safe ones.
I think (don't really know) alloy steel valves and hardened seat were pioneered by the aircraft industry and appeared in cars by the 1950's. So really lead wasn't needed to extend the life of valves after that. Also my experience with some shitty 1960's cars was the valve guides would wear out before the seats. Compression is fine but engine burns oil and fouls the plugs. You could see it with older cars when going downhill, they'd be blowing oil smoke.
No idea about 240z specifically, but at least things designed for sustained high performance (like aero engines) tend to use valve seats made from some wear and temperature resistant alloy like stellite or brightray.
Legally, they need to run a fuel which is approved on the type certificate data sheet for their engine (and the engine-airframe combination).
The recently developed G100UL unleaded fuel requires a change to the type certificate of the airplane (by serial number) and engine(s) (by serial number) to be legal.
Until that supplemental type certificate existed, these airplanes did legally need leaded fuel.
No, G100UL is a full drop in replacement that meets the standards off AVGAS which is what is required by the certificate. Fully legal on all engines with no change to the certificate.
It does not meet the composition standard of 100LL, which is why you need to buy an STC (Supplemental Type Certificate) from GAMI to use it legally in an aircraft. (It is a drop in replacement from a performance point of view, but does not meet the original type certificate fuel standard.)
