Light Aircraft Association

Lycoming Service Instruction 1070S issued on 24 April 2013 now permits many high compression 0-320s to run on UL91. My question is do I need any more authorisation or can I go ahead and use UL91 now in my o-320-b?

If your engine is on the list. 'Fill your boots' or, your tanks, and away you go.

Nothing else needed.

John.

PS If you are going to run UL91 only, Change your oil and filter. You will be surprised how cleaner your oil will become over time.If you are going to run both UL91 and 100LL don't bother.

I see that the approval now runs to many IO540s including the D-series. Good news for us RV10 owners/builders!

I have heard the Half penny Green has pulled UL 91 saying that it was too costly , at leicester at the AGM they said it cost more than 100 LL , Is this true and why ?

Jet stations near me are ethanol free at the moment ....................

Murco garages in southern England are also still selling alcohol free unleaded (but always double-check!)
Tony Nowak

Useful to know Tony but UL91 is Avgas, not Mogas, and as such can be used without having to get the approval that is required to use Mogas. There are over 30 airfields in the UK now stocking UL91 and that number continues to grow. I have no knowledge of the wholesale price, but as it was initially shipped up from the south of France by road tanker - it is now shipped in by road from Belgium I believe - it could well be a little more than 100LL which is refined in the UK. Apparently the big guns in the Avgas world want a 100UL to replace their 100LL and that is technically challenging, hence they have not jumped onto the UL bandwagon. I have heard that UL91 may eventually become UL94 as its current rating is already a little over 93 and it only needs a little tweak to get to 94. With such a large number of engines happy on 91 I do wonder whether there really is a requirement for a replacement 100.

Kevin Dilks wrote:I have heard the Half penny Green has pulled UL 91 saying that it was too costly , at leicester at the AGM they said it cost more than 100 LL , Is this true and why ?

UL91 is available at Sleap Airfield (EGCV) in Shropshire, about 10 miles N. of Shrewsbury.

We have quite a number of Rotax and Jabiru powered aircraft on the field whose owners were demanding it.

It costs around the same as our 100LL as the airfield buys it in smaller quantities, but despair not: it's partly because our 100LL is around the cheapest in the country!

Come and visit us, and don't let the Shawbury MATZ put you off - that's normally only active 9-5, Mon-Fri.

What difference is there between ul 91 and unleaded without ethanol

UL91 is AVGAS. As such, it is cut to give it a lower vapour pressure to help avoid vapour lock.

On the legal side, your aircraft needs to be approved for MOGAS and the appropriate mods and paperwork completed to use unleaded. For a Lycoming at least, SI1070 gives approval for types to use UL91.

The confusion may come from the fact that initially blanket approval was given for all Lycomings approved for MOGAS to use UL91. Since then, SI1070 has been updated and includes many other types not approved for MOGAS - such as many IO540s.

howell wrote:What difference is there between ul 91 and unleaded without ethanol

A load of checks all along the production and supply chain and the associated paperwork.

I'm sure there's more to it than that, but the above does explain some of the extra cost involved.

The paperwork does have its uses: if there is a duff batch of fuel that gets into the AVGAS supply chain it can be traced right to the aircraft.