Comments by "Keit Hammleter" (@keithammleter3824) on "Scott Manley" channel.

Lots of farmers in Australia own light planes in order to conveniently and quickly visit large towns and cities. Many of them run their planes on 98 octane retail gasoline meant for cars, as it is available everywhere, and farmers buy it in 80 litre drums for their cars and farm equipment. Toluene is the additive used to obtain 98 octane rating. It is illegal to use car gasoline in aircraft, but aircraft engines run on it just fine. In theory, aero engines run on car gasoline could have high valve seat wear, but farmer-owned planes don't clock up anywhere near enough hours for it to matter. Cessna stopped making 152's and 172's in 1985 but considerable numbers are still registered and flying. The main differences between car gasoline and avgas is the use of tetraethyl lead instead of toluene to achieve the required octane rating, the absence of various proprietary additives to reduce wear that is used in car gasoline, and manufacture of avgas to higher quality standards to ensure purity, absence of ash, etc.
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@spannaspinna I was talking about the Cessna 172 popular with farmers. Most would have the Continental engine. I doubt a typical farmer would bother with supplemental type certificates. They are a pretty go-ahead-and-do-it mob who dislike what they see as government red tape and taxes. Last I heard, using car gasoline was just not permitted - an STC is not applicable.
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@DaBoomDude Yes, they stopped mass producing them in 1986, then restarted making small numbers 10 years later. They are a good aeroplane for farmers and cattle ranchers, but for hobby flyers they were priced out of the market by ultra lights and other competition.
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@tonylam-u1t Indeed, the FAA has no jurisdiction in Australia (obviously), however Australia's equivalent, the Civil Aviation Safety Authority (CASA) uses the same terminology - we have STC's in Australia too.
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@tonylam-u1t Re your post beginning "When you said the engines "...." - on fuel tolerance and knocking - true. Although in Australia there are still plenty of old cars still in use that have no engine management computer and require 98 octane. And, hilariously, there are enough ning-nongs who own modern cars and think that getting an extra 1% power is actually worth the cost to make it worthwhile selling 95 or 98 octane. And apparently, it is a common misconception that higher octane rating means higher quality. The marketing by some fuel companies includes hints that support this misconception. I bought a cheap Chinese-made portable generator. I was surprised and annoyed to discover it needs 98 octane fuel. Pinging is quite noticeable on 91 octane fuel. There is no way to adjust the ignition timing - it is what it is. Incidentally, gasoline marketing in Australia is a funny thing. There are only two refineries, and each of several brands get their gasoline from those two refineries. Each claims its gasoline has some exclusive magic additive, but it really doesn't matter what big sign is on the service station - BP, Caltex, Shell, Ampol etc - it's the exact same juice every time. Until recently BP operated a refinery in WA, and ALL service stations in that State, regardless of branding, got their gasoline from that refinery. There are a couple of independent minor brands who import gasoline from whichever Asian country supplier gives them a good deal from time to time.
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@tonylam-u1t Incidentally, some people make more of pre-ignition and valve seat wear from not having lead than is warranted. In Australia prior to the first phase of emissions regulations in 1974, and when retail gasoline had tetraethyl lead and thus coloured red, and most cars were intended to run on 98 octane, there was another kind of gasoline used - government pool gasoline. This was just the same as normal leaded gasoline, but made to a government specification that omitted tetraethyl lead. Supplied by BP or Caltex, it was dyed yellow so you could tell if some guy was running his own car on stolen fuel. I don't know the octane rating as it was not published, but it was probably about 85 - 90. All cars and light trucks owned by government departments ran on it unless based in small rural towns. Some manufacturers, eg Ford, supplied the government with a special low compression head on the engines and they ran perfectly fine. Some GM (known as GM-H in Australia) engines were fitted with two head gaskets to lower the compression a bit, and they were timed differently. Mechanics would forget and set the timing as per the standard engine and these engines would then ping (pre-ignite) a lot on acceleration. When the Holden (GM-H equivalent to Chevy) EK model came out, it had a higher compression bored out version (138 ci) of the engine they had been using - a 132 ci derivative of the old Stovebolt. For government cars they continued to supply the old engine, as it ran fine on pool gasoline and the new engine pinged. Or maybe the government just wanted the small engine and GM-H had some left. Did engines that were run on pool gasoline wear out faster or suffer valve seat problems? Well, no, they didn't. They lasted about as long as the same engines ran on leaded gasoline. A work colleague had a vintage Fiat car. I once asked him if he used the additive to prevent valve seat wear. He said no, his Fiat was designed to run on the cheapest grade Italian gasoline, which was not leaded. At one stage I bought at a government auction a used Holden EK Special that had been a chauferred car. It had, consequently, the low compression low capacity 132 motor and the GM 2-speed auto transmission (same as the Powerglide in the US). It had 100, 000 miles on the clock, was in perfect condition, and ran real sweet. But it sure was gutless.
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@tonylam-u1t The difference in rocker height from installing two head gaskets is well within tappet adjustment range. When GM-H increased the bore and compression in about 1960, the increase in compression was achieved by shaving off a few more millimetres from the interface surface - more than a head gasket's thickness. The same part number push rods were retained. A common cheap way to hot up the earlier engine was to fit a head meant for the later engine - you don't have to change anything else. If you buy the later but worn out or damaged engine from the wreckers you get another carby and usually the head is good. Higher compression and twin carbies make for a car nice to drive. The red colour in red gasoline comes from tetraethyl lead. Perfectly good in any gasoline engine but not permitted to be sold in service stations around the World. Australian farmers get their fuel free of excise too, as do mining companies. But they must buy from outlets that cater for them. At one time farmers could get fuel from a service station and then claim a rebate, but I think that was abolished. What is a tappet? A pet dog that makes a tapping noise by hitting the floor wagging his tail while lying on it.
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@andrewwallenstein9575 It seems that you have difficulty reading, as well as being completely wrong. Look at the 4th word in my post that started this thread. It is "Australia." In Australia there are 4 kinds of gasoline available: 1. Standard car engine fuel. This is gasoline with toluene added to raise the octane rating. Trace amounts of oil (to lubricate the fuel system) and proprietary substances claimed to reduce wear. 2. Opal car engine fuel. This is the same as standard fuel but has no toluene, because some districts have banned toluene. The octane rating is obtained purely by cracking or blending and/or adding benzene. 3. Avgas. this is gasoline with small amounts of benzene added to raise the octane rating to 100. It is made to higher standards of quality control and purity than car fuel. 4. White spirit. This is pure gasoline not suitable for engines (except the earliest vintage cars) and is used as an industrial cleaning solvent You can verify the above by down loading the Material Safety Datasheets (MSDS) from maker's websites. For instance, BP's MSDS for avgas states on page 1 it contains <0.1% benzene. Their MSDS states in Section 3 on page 2 that 95 octane car fuel contains gasoline plus up to 20% toluene. Gasolene as sold is a mixture of linear chain molecules of carbon and hydrogen. It would contain other things, such as carbon ring compounds and naptha, and sulphur but the refinery takes these things out. Hence the combustion chemistry in engines is the same regardless of fuel type. Though a variety of simultaneous reactions (in theory an almost infinite number, but about 8 are the important ones), the hydrocarbon chains are split up, a range of intermediary compound formed, ending up with carbon dioxide and water vapor. The additives to raise the octane rating, tetraethyl lead, benzene, toluene, affect the relative rates of the competing reactions, but actually have a tiny effect on the process. The red colour in older gasoline is the tetraethyl lead. Gasoline itself is colourless. The red deposits that used to appear in carburettors is tetraethyl lead left behind when the gasoline evaporated.
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@andrewwallenstein9575 Cessna does NOT make a lot of 172's. Production is typically 100 to 150 per year. Prior to 1986 they mass produced them in the thousands. Look up the number made in 2023 - it was a good year - they made 180. The reason is not hard to see. In its heyday the 172 was cheap and had the market to itself. A new 172 costs about half a million dollars, putting it clear beyond what farmers and cattle ranchers can afford. And if you can afford the cost of a 172, you can get a 2-engine DA42 Twin Star for a bit less, or a Tecnam P2006T for about the same price - both safer and better. In 1968 a Cessna cost about half as much in inflation adjusted dollars. My wife, who was checked out on many piston light aircraft, used to deliver planes from the dealers to the purchasers. She's never seen a post-1996 172.
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@jayjaynella4539 And it causes cancer in addition to rotting your brain.
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@tonylam-u1t "No way" means just that - there is no way to adjust the timing. On the small engines I was talking about the ignition system is sealed in a block of epoxy that bolts next to the flywheel, and has a lead coming out of it that connects to the spark plug. I suppose one could discard it and make up some sort of kettering ignition or magneto and install a set of points for it, but why on earth would I or anyone else bother? Cheaper and simpler to just run it on 98 octane fuel. Or one could completelt strip down the engine, pull out the ignition locating pin, fill the hole and the bolt holes with weld and drill new holes, then put the engine back together, but why would you bother? you would have to be a nut.
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@tonylam-u1t You need to read more carefully. I never used the word "impossible." Any sensible person would understand "there is no way to adjust the timing" as meaning "The engine manufacturer did not provide a way to adjust the timing." Actually, have thought of a simpler way to alter the timing. Remove the flywheel and re-machine it so it goes back on slightly rotated by a shim. But, again, no sensible person is going to do that. Not worth the effort.
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@spannaspinna In the car engines I was talking about, which were pre-ECM, of course there is the usual timing adjustment. Where i was talking about there being no way to adjust the timing, I was talking about modern small Chinese made engines - a fact that is clear if you read the post where I brought that up. On these engines the entire ignition system is molded in an expoxy block that bolts to the engine block very close to the flywheel, and there is no way to adjust the timing. As the system is electronic and has no points, the Chinese engineers most likely decided there is no need of an adjustment. As far as up to date Western ECM cars go, you don't adjust the timing in the traditional way. You can, if you know how, change the ECM programme parameters. I don't know about the USA, but here in Australia doing so is illegal, as it would affect emissions.
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@robboardman598 No, tetraethyl lead is red in colour. If you have worked on an old car that has a carburettor, you will know that carbies often used to accumulate a red deposit on various surfaces, whereas they don't now. Mechanics were trained to avoid skin contact with the red deposits because that was oxidised tetraethyl lead, which is poisonous.
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@robboardman598 Yeah, you said that before. Lead oxide, PbO, has 2 phases, red and yellow) and requires temperature >600 C to form, But no combustion occurs in a carburetor. Therefore the red deposits that occur in carburetors (and sometimes in intake manifolds) cannot be the result of burning tetraethyl lead. However, Lead tetroxide or red lead, Pb3O4, is also red. It is formed artificially in a series of reactions starting with PbO, which as stated cannot form in a carburetor.
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At 2:25 Mr Manley says that car engine gasoline is at best only 90 octane. Things must be very different in the US, or he has no idea. I suspect the second case. Here in Australia, 98 octane gasoline is available at every service station. The difference between 98 and 100 in terms of engine operation is negligible. The reason why it is 98 and not 100 is historical - that's what retail leaded gasoline was. At least in Australia, toluene is the additive used to achieve 98 octane rating, which is a disgrace, because toluene is far nastier than lead. Because street kids tend to sniff gasolene to get high on the toluene, toluene dosed gasoline is banned from sale in some areas. A 98 octane fuel known as "Opal" is sold instead. The government banned lead in gasoline because it was thought that car engine exhaust fumes was causing high blood lead levels in people. It was not done because of catalytic converters, because they came into use much later. But banning lead made no noticeable difference. It is now known that most lead in blood comes from house paint, and the dust spread about in transporting material from lead mines. A significant amount of lead in the environment comes from buried telephone and power cables. Lead, for about 50 years, was considered the ideal material for cable sheaths, until replaced by nylon in the 1970's. Over decades the lead is lost from the sheaths and ends up evenly spread in the soil. Eliminating lead from gasoline did have a small beneficial effect on blood lead levels in the USA due to their high population density (10 times that of Australia, for example), and their use of gasoline in light trucks and busses, which have always almost been invariably diesel everywhere else in the World. Hence their use of gasoline reckoned on quantity per year per area of land is about 15 times that of Australia
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@scottmanley Aha! Australia uses the "Research Octane Number" the same as most countries. RON is determined by using the fuel in a standardized test engine with variable compression - compression is varied to discover the maximum compression that does not show pre-ignition. US retail gasoline stations for some reason display the "Motor Octane Number" in which the point of compression ignition in a standardized engine is determined by retarding the spark until pre-ignition occurs. A 98 RON fuel is approximately the same as a 86 MON fuel.
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