Did you know that about two-thirds of piston-engine aircraft are eligible to use UL94, an unleaded aviation fuel that’s better for your engine, better for the environment, and is actually cheaper to buy than 100LL? Even better, did you know that UL94 fuel has been available at San Carlos for the past several years? If this all comes as a surprise, read on, because every pilot or owner a plane that can use UL94 should consider switching to it.
For years, a number of aviation fuel companies have been working to create an aviation fuel to replace 100LL (the LL means “low lead”) which eliminates the small amount of lead which it contains. Tetraethyl lead is added to 100LL to increase its octane rating and prevent engine knock and wear in high-performance engines. Everyone agrees that we should work to reduce and ultimately eliminate the use of lead in aviation fuels, much as we eliminated lead from automobile fuels and paints in the 1970s.
It turns out the designing a fuel that will provide the 100 octane (needed by some high-performance engines) without adding lead is a tall order. Several fuel companies have been working on this for many years, and the first unleaded 100-octane avgas was certified just this year for a few aircraft models. That fuel – called G100UL – is not yet commercially available and it will probably be a few years before it is in wide distribution. There is a second unleaded 100-octane fuel from a different vendor, Swift Fuels, reportedly also nearing FAA approval. One or both of these new fuels may eventually replace 100LL, but that is likely years away.
But the majority of small planes – about 65% – have engines which do not require 100-octane fuel, or the lead used to boost its octane level. Most of our planes were originally certified to use 80/87 octane or 91 octane fuel, and can use Swift Fuel’s UL94, which, it turns out, has been available from Rabbit Aviation at SQL for the past several years. Examples of planes which can use the 94UL fuel include many Cessna (152, 172, 182, 210 and more), Piper, and Grumman models, as well as a huge list of other aircraft.
Why would you want to switch to UL94? Well, first off, it’s unquestionably better for the environment, but beyond that, there are tangible practical benefits to switching. At the top of the list: eliminating lead Is good for your engine. No more lead-fouled spark plugs, no more extra wear caused by lead. Longer oil change intervals are possible, and spark plugs will last longer. And unleaded fuel leads to engines that live longer. The engine manufacturers agree, and both Lycoming and Continental have endorsed unleaded aviation fuel use in a long list of their engines.
There is speculation that switching to unleaded fuel may eventually allow engine time-before-overhaul (TBO) hours to be doubled from current levels. Imagine that – a 4000 hour TBO! Even better – at least for now, 94UL is cheaper to buy than 100LL at San Carlos. This is, in part, because the County of San Mateo is not charging a fuel flowage fee on 94UL to encourage its use.
What does it take to switch? First of all, 94UL is completely mixable with 100LL in any proportion. So you can buy 94UL at airports which sell it (in our area, that currently includes SQL, RHV and WVI) and buy 100LL when it’s your only option, and your plane will run just fine. 94UL fuel is slightly heavier than 100LL (6.3 lbs/gal instead of 6.0 lbs/gal) but contains slightly more energy per gallon. It is not tinted and so is a straw-like color. 94UL contains no ethanol or anything else that would cause problems with hoses or gaskets.
Many planes will need a one-time Supplemental Type Certificate (STC) in order to legally use 94UL. The easiest way to see if your plane can use 94UL and whether or not it needs the STC is to look up your make and model at swiftfuelsavgas.com/stc/. If you need the STC, it’s $100 – one time – and that price includes any future STC that might be required for Swift’s upcoming (but not yet approved) 100R fuel, which is designed to replace 100LL for all piston aircraft.
The STC includes everything you’ll need, included new placards to be placed near your fuel ports to indicate that the aircraft is approved for 94UL. If you need the STC, an A&P will need to sign the included Form 337 and return it to the FAA, along with a logbook entry. That’s it; aside from the placard, no change to your plane is necessary.
Swift Fuels has a website where you can find answers to most questions you may have. It is important you check to be sure you can legally use 94UL in your plane, and to obtain the inexpensive STC if necessary, in order to be legally compliant. The website is at swiftfuelsavgas.com. There you can also find lists of Lycoming and Continental engine models which are approved for UL94.
This is that rare example of a new aviation product that’s good for you, good for your plane, good for the environment, good for our neighboring communities, and it even saves you money! Hopefully we’ll soon see a 100 octane unleaded Avgas that can satisfy the most powerful of piston engines, but until then, UL94 is a great solution that can help make many of our planes, and our airport, cleaner, greener, and a better neighbor.
