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What’s the difference between 100LL (low lead) and just 100 aviation fuel?

Normally I use 100LL in a Cessna 150 or 172, but if I go to an airport that only has 100, is that going to make much of a difference?

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Tags: Aviation Fuel, Cessna 150, Lead

10 Responses to “What’s the difference between 100LL (low lead) and just 100 aviation fuel?”

Robert O says:

July 5, 2009 at 9:40 am

you’ll be ok. av gas is very dry.

hdr says:

July 7, 2009 at 11:11 am

100 avgas is 100LL. If you’re unsure, just ask the fuel jockey.

jed slade says:

July 7, 2009 at 12:09 pm

It should make very little difference, but you may notice it in the performance,in take off,banks turns etc if you are extremely in sinc with the kite.

cherokeeflyer says:

July 7, 2009 at 8:34 pm

Avgas 100 is The standard high octane fuel for aviation piston engines. It has a high lead content and is dyed green. There are two major specifications for Avgas 100. The ASTM D 910 and UK DEF STAN 91-90. These two specifications are essentially the same but differ over antioxidant content, oxidation stability requirements and max lead content.

This grade is the low lead version of Avgas 100. Low lead is a relative term. There is still up to 0.56 g/litre of lead in Avgas 100LL. This grade is listed in the same specifications as Avgas 100, namely ASTM D 910 and UK DEF STAN 91-90.
Avgas 100LL is dyed blue

Avgas is gasoline fuel for reciprocating piston engined aircraft. As with all gasolines, avgas is very volatile and is extremely flammable at normal operating temperatures. Procedures and equipment for safe handling of this product must therefore be of the highest order.

Avgas grades are defined primarily by their octane rating. Two ratings are applied to aviation gasolines (the lean mixture rating and the rich mixture rating) which results in a multiple numbering system e.g. Avgas 100/130 (in this case the lean mixture performance rating is 100 and the rich mixture rating is 130).

In the past, there were many different grades of aviation gasoline in general use e.g. 80/87, 91/96, 100/130,108/135 and 115/145. However, with decreasing demand these have been rationalised down to one principle grade, Avgas 100/130. (To avoid confusion and to minimise errors in handling aviation gasoline, it is common practice to designate the grade by just the lean mixture performance, i.e. Avgas 100/130 becomes Avgas 100).

Some years ago, an additional grade was introduced to allow one fuel to be used in engines originally designed for grades with lower lead contents: this grade is called Avgas 100LL, the LL standing for ‘low lead’.

All equipment and facilities handling avgas are colour coded and display prominently the API markings denoting the actual grade carried. Currently the two major grades in use internationally are Avgas 100LL and Avgas 100. To ease identification the fuels are dyed i.e. Avgas 100LL is coloured blue, while Avgas 100 is coloured green.

Very recently a new Avgas grade 82 UL (UL standing for unleaded) has been introduced. This is a low octane grade suitable for low compression engines. It has a higher vapour pressure and can be manufactured from motor gasoline components. It is particularly applicable to those aircraft which have STCs to use automotive gasoline.

eferrell01 says:

July 9, 2009 at 10:53 am

If your engines were designed or modified to run on 100LL, it should work well with 100. If it is still capable of being STCd for auto gas, you may have more trouble from the 100. 100 has 1.12 grams per liter of lead, and 100LL has .56 gpl. 80/87 has only .5 gpl.
The more lead in the gas, the more lead fouling you will get on your spark plugs. If you have to burn the 100, don’t lean unless you absolutely have to. Lead does not burn and a rich mixture will flush it out the exhaust rather than coat the valves or sparkplug electrodes.

Mike says:

July 9, 2009 at 6:01 pm

not unless you dont like the color

Ben Dere Dun Dat says:

July 12, 2009 at 2:05 am

There should be a section in the Pilots Operating Handbook / Flight Manual / owners manual of each plane you fly that tells you exactly what fuels are approved and can be safely used, so you should refer to that.

In the USA, the chance of you encountering anything other than 100LL (blue) is very slim. If you ever do encounter the 100 octane leaded variety (green), it is perfectly safe to use in your Cessna 150 / 172.

By the way, the answer above regarding lead fouling missed an important point. While lead does not burn, it is adequate EXHAUST SCAVENGING that is a major factor in preventing lead fouling of the spark plugs. For proper scavenging (purging unburned exhaust residue from the engine), one needs to keep the idle speed on the ground above 800 rpm and reduce ground running time as much as possible. Older aircraft (such as my 1959 C-172) are particularly prone to fouling, even on 100LL.

Adam R says:

July 13, 2009 at 7:51 pm

tetryethel lead content

JJ Joseph says:

July 16, 2009 at 10:27 pm

In theory, both grades are available, but you’ll find that 100LL is the only grade available almost everywhere.

frank m says:

July 19, 2009 at 4:10 pm

about 14 cents a gallon.

Pilotage Moto

What’s the difference between 100LL (low lead) and just 100 aviation fuel?

10 Responses to “What’s the difference between 100LL (low lead) and just 100 aviation fuel?”

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