My studies of fuel are a couple of years old now, but I did a lot of work on it for the worlds #2 car manufacturer. This included interviewing the head fuel technologists at a number of the oil companies. At the time BP only made 98 at Kwinana, but things might have moved on.
While BP may supply Caltex in QLD my point is that its not exclusive and if the spot market is favourable it will be substituted with Singaporean fuel. Also BP supply California with fuel from time to time depending on US supply and exchange rate, so there are times when BP does not have any excess capacity to supply other brands.
For my money, I only buy BP, Shell or Mobil and only from high volume sites. I also frequently have to supply fuel specifications to clients and my experience is that BP, Shell & Mobil have the most easily accessible specification sheets and have accessible fuel technologists when I require specific clarification. In the past we have also conducted batch testing of commercially available fuel from a variety of service station sites. As I noted earlier, the quality between different service station can be significantly different.
Having said that, the United 98 octane is very good and the guys next door get more power on engines on the dyne than the BP racing fuel. But, it contains ethanol, so its neither suitable for aircraft or any of my cars.
Regarding aircraft valves, I cannot disagree more. Get an old aircraft pot and take it to a race engine guy or cylinder head modification guy and ask what they think. The valve seat profile (ie seat angle and the contours leading to and from the seat) is very old fashioned. The UN paper talks to this, which is why I included it.
This is what Continental say:
In such fuels, the lead acts as a lubricant, coating the contact areas between the valve, guide, and seat. The use of unleaded auto fuels with engines designed for leaded fuels can result in excessive exhaust valve seat wear due to the lack of lead. The result can be remarkable, with cylinder performance deteriorating to unacceptable levels in under 10 hours.
I forget the timing, but at least Continental made a change to its valve seat material a few years ago. Car engines started moved to hardened seats and modified valve profiles in the late sixties / seventies, but it really got going in the late eighties when catalytic converters became mandatory, which is why the reports such as the 2012 UN one don't report problems moving to unleaded fuel, as I said I included it because of its very nice explanation of seat design. Aircraft engines started changing seat materials sometime after 2000. The problem is that many GA aircraft can have engines with over 20 years calendar life and therefore are in the pre-hardened seat era.
The FAA AVGAS transition committee is concerned about valve recession of replacement fuels and deems testing of this as required.
Peterson Aviation (who hold 20,000 MOGAS STC's) and who are probably the major proponent of unleaded fuel say:
However, lead has also been found to protect valves and seats against valve seat recession.
This Swedish paper agrees
https://gupea.ub.gu.se/bitstream/207...gunwpe0019.pdf
The crucial
question is therefore whether or not a car with soft valve-seats can use unleaded gasoline.
This matter has been under heavy investigation. It seems to be a matter of interpretation since
conclusions differ between studies, the results are coinciding. One fact that
researchers, oil companies, and vehicle salesmen agree upon is that only 0.05g lead per liter is sufficient to prevent VSR (McArragher et.al., 1994).
This paper by Barlow:
says:
"The lead compounds, oxide and sulphate mixtures resulting from combustion proved to be the most effective lubricant for cast iron or unhardened valve seats ever produced. here is also another less well documented but none-the-less crucial benefit, ie the lubrication of the bottom of the valve guide...."
The previous papers are based on the Swedish experience which was the first country to phase out leaded fuel in the 1980's. The paper by Barlow documents real world engine wear examples from removing lead which include valve seat wear, valve burning and turbocharger wear. I hadn't read this before, but apparently lead forms a protective coating on the turbocharger impeller.
Here's another one
http://www2.isye.gatech.edu/~vthomas...ation_lead.pdf
A secondary role of lead additives is lubrication of the exhaust valves.
The most extensive study of the car maintenance consequences of using unleaded gasoline in cars designed for leaded gasoline was a 5-year study of 64 matched pairs of cars (62).
cylinder heads were replaced more often on the cars using
unleaded gasoline,because of excessive valve-seat wear
Laboratory studies confirm that under prolonged, severe driving conditions,valve-seat recession will occur if unleaded gasoline is used in engines without hardened valve seats