Why do we still refer to it as 'unleaded' gasoline?

From the Environmental Protection Agency’s website:

However, this is from a January 1996 press release. I know of no sales of leaded gasoline now even for the uses described above. They simply use a higher-octane unleaded gasoline.

Lead was always an additive. It has been virtually nonexistant for years now in the U.S.

So why do all the pumps still emphasize that they are selling “unleaded” gasoline?

Isn’t that sort of like labeling diet soda “saccharine-free,” or referring to hydrogen-free blimps?

Wouldn’t it make far more sense to make the special designation the one for “leaded gasoline?” Which, again, I haven’t seen sold anywhere, gas station or marina, in years and years.

[aside] I remember when the switch was made and there was Regular and Unleaded gas. Each came in three grades, one of which was “regular”. So, depending on the brand (Sunoco, Gulf, BP, etc.) you could but Regular Regular or Regular Unleaded! Talk about confusion!![/aside]

In the Netherlands and several other European countries, we refer to unleaded as Euro 95 or Euro 98 (although the Germans also seem to stick to their Bleifrei) - depending on the octane level. I don’t think you can buy leaded here anymore either, although gas stations DO sell synthetic lead replacements. Some classic cars can’t run on unleaded fuel, and need a jug of the synthetic stuff in addition to a full tank. Friends with classic cars tell me it works as good as the real thing.

I suspect the reason “they” are adamant about labeling unleaded gas so clearly is because if you mistakenly put unleaded gas in an engine that requires leaded gas bad things will happen to the engine. The opposite is not true: engines which can take unleaded gas work fine with
leaded gasoline - albeit with more pollution and probably worse performance.

Clearly, not many engines today require leaded gas except maybe a few farm vehicles although I suspect this is less true in more rural parts of the country.

The primary purpose of lead in gasoline was to aid in cooling and lubrication.

Be advised that running your modern car on leaded might not damage the engine per se, but it WILL destroy your catalytic converter. Damn expensive to replace.

While I agree with you, using the term “unleaded” rather than “regular” makes the oil company sound more progressive and environmental, which they couild certainly afford to be. Like those Shell ads with prominent happy black people after their fiasco in Nigeria.

Good point, although note that I said

“engines which can take unleaded gas work fine…”

The engines can handle it just fine, it’s the cataltic converter that will be unhappy.

Airports still sell something called Low Lead fuel. It’s the “regular” fuel that gets pumped into piston powered aircraft. Most of which require leaded fuel.

Actually, I just happened to notice the last time I got gas that the pump wasn’t labeled as “unleaded.”

You mean you’re supposed to replace your catalytic convertor?

You can still buy leaded aviation and possibly race gas.

>> The primary purpose of lead in gasoline was to aid in cooling and lubrication

Nope. It was to raise the octane number and prevent knocking.

Actually, the old style “lead”- tetrethyl lead- was partly an octane booster but primarily a valve face lubricant.

Under high-load conditions, the face of the exhaust valve can get nearly-glowing hot. As the valve slams shut, it actually sticks to the seat- microscopic areas basically get “welded” together between the two. The next time the valve cycles- a fraction of a second later- it tears out those microscopic welds.

What this causes is seat erosion. The face of the combustion chamber, that the valve seals against during firing, wears away, and the valve itself receeds further and further into the cylinder head.

After 1971 or 1972 or so, most auto makers were using one form or another of “hardened” valve seat, which better resisted the erosion.

If you have a pre’72 classic that you drive regularly, a small bottle of any of the commercial “lead” replacer additives- true tetrethyl is illegal as a motor fuel additive these days- will help prevent the seat erosion.

GuitarDave: You have that backwards. If you run unleaded in a car designed for regular- meaning made before '72 or so- you’ll suffer no problems whatsoever. Unless, as I mentioned above, you run it for a long time, like 50,000 miles, on nolead in which case you’ll see valve problems occuring.

However, if you add leaded to a more modern car with a catalytic converter, exhaust gas temperature sensor, or exhaust oxygen sensor, those items will be essentially rendered useless within one tankful of leaded.

In all cases, the lead coats the sensor or the catalyst mesh in the converter, after which they no longer work properly. And no, there’s no easy way to clean the lead off- the parts must be replaced.

A lot of small airplanes still use leaded fuel, commonly referred to as “100LL”

It is used to raise octane (which reduces knocking) as well as to provide lubrication in the valves. All the “certified” aircraft piston engines from Lycoming and Continental require 100LL or better “avgas”. A small number of such engines have been converted to unleaded premium “mogas”, but these engines wear out faster (according to the mechanics I’ve spoken to) and with new ones costing in the neighborhood of 30k-40k… well, most aircraft owners would rather not do this, apparently.

Homebuilt aircraft and kitplanes may, however, use engines that take unleaded gas. (I once took a trip with a friend to Hartfield, WI where, after we landed, we discovered the airport was no longer selling fuel. We spent much time locating a gas station selling premium grade gas, then more time arguing with the attendant about how we were intending to transport 26 gallons back to the airport)

I seem to recall a few years ago they started referring to unleaded gas as regular, but it doesn’t seem to have caught on entirely. For a while, I remember there being unleaded and regular, then when regular was mostly phased out (I’m thinking this would be the late eighties or early nineties) the convention switched to regular meaning unleaded. Certainly no one now would see a sign advertising regular and assume they meant leaded. I think the change was somewhat official, so I’d imagine that there’s some sort of paper trail left to follow.

Doc, we’ve gotta stop running into each other like this. :wink:

Leaded gas is no longer needed in a pre-72 vehicle if you replace the valves, which does not cost much (like $100 or so). It is pointless to run a pre-72 vehicle with the stock valves when it’s so easy and cheap to ‘get them in shape’. Leaded gas is available for airplanes, and any gasoline over 116 octane must be leaded, un-leaded cannot go above 116 octane unless (forget the name of the chemical) is added, but I do believe it is illegal to sell gasoline with this chemical pre-mixed. Damn. Wish I could remember it’s name… You can buy it in hardware stores and can add it to your tank before filling to raise your octane by about 10-15 octane ratings, depending on how much gas/what grade it is you buy. This additive is often used as a cheap substitute for red, blue, or green race gas, which is hard to find in most cities. Many high-performance vehicles, especially super- and turbo- charged ones, run extremely high octane gas at the track so as to not detonate under high boost. Octane boosters sold in hardware stores that promise to raise your octane by, say, 5 points are misleading. ‘5 points’ is actually 1/2 of one octane rating. It’s a waste of money.

The lead was not really to raise the octane, it did, but it was consequential. Once the lead was removed, the gas was simply made at a higher octane. It was never necessary as an octane enhancer. As Doc Nickel elaborated, it was mainly to lubricate the valve seats and prevent erosion.

I do believe (but I’m not a pilot so may be wrong) that 100LL is “blue” gas, 110 is “red” gas, and 116 is “green” gas. I may have the colors backwards.

Excitableboy, it is illegal to replace your catalytic converter if your vehicle has less than 100,000 miles. Normally replacement is not necessary unless it becomes clogged due to abuse or damage (such as hitting a big rock and destroying the innards). You may not legally run without a cat, on-road, in any state that requires vehicle inspections. You may run off-road with a ‘test-pipe’, or exhaust piping that eliminates the cat.


Technically, Homer, one doesn’t replace the valves (unless they’re worn too far to safely grind.) Instead one replaces the seats, typically by having the old seat area machined out and having a ring of hard material, such as Stellite, pressed into place.

And I don’t know about you, but by the time I’ve pulled the heads off, had them machined, the valves and guides redone, and reinstalled them with the requisite head, intake and rocker cover gaskets, the total bill is typically far more than a mere $100. (It cost me $165 the last time I had a set of small-block heads done, just with guides and a valve job. That didn’t include gaskets, etc.)

And in some cases that’s not an option, since the owner prefers to preserve the car’s originality. Would YOU yank the original head of a '53 Blue Flame Six for the first time since it was assembled, out of an otherwise-totally-original car, just to have the seats replaced? :smiley:

I know a couple of people in similar situations with LS-6s and Boss 302s. They’re worth more as original.

The stuff you supposedly buy in hardware stores is either Naptha or Toluene. Both are expensive- comparatively at upwards of $8 to $10 a gallon- and can damage old rubber components (such as fuel hoses and pump diaphragms.) Their octane improvement is something of an urban legend… In the early seventies’, the legend was that you could jack up the octane with moth balls- which contain napthalene, as I recall.

Of course, if you tried it, you got a gummed up carb and fuel that burned poorly and incompletely.

Airplane gas:

red - 87 octane
blue - 100
green - 115 or 120, I forget the exact number

But pretty much all you can find these days is the blue stuff. Everyone I know who has an engine rated for red gas runs it on blue because they can’t find red anymore. I hear you can find green out in Hawaii.

The color is a dye to let you know what grade the fuel is. Jet fuel is clear. Kind of important not to put jet fuel in a piston engine and vice versa.

Illegal? Cite, please.