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Mixing UL91 / 91UL and 100LL, and need for additive LW-16702, or Aeroshell 15W/50

Peter wrote:

the problem with empirical data is that


The price difference between e.g. Aeroshell W80 (without the additive) and W80+ (with the additive) is so small that it doesn’t make sense to chance that Lycoming is wrong in claiming that you have to use the additive.

ESKC (Uppsala/Sundbro), Sweden

and W80+ (with the additive)

Or 15W50…

Interesting thread. I bet very few people knew this.

Is there anything out there regarding the alleged risk of combining LW16702 with Camguard?

Shoreham EGKA, United Kingdom

A_and_C wrote:

What aircraft type would this be for ?

Its a rockwell commander, looking for “UL 91/94/96” placard to cover all grades.
If you make them generic (without a/c type on them), I am sure there will lots of takers.

United Kingdom


I have pass your suggestion on to the guys who deal with the graphics and they are currently looking at the generic placards in red with white graphics.

Being Robin operators we have a template for production of 91UL/100LL placards that also carry the fuel tank capacity data and look identical to the factory placards. These are available in any colour to contrast with the aircraft background colour.

Peter wrote:

Interesting thread. I bet very few people knew this.

I know dozens of people who over the years have run, and still do run, their Jodels on Mogas and not one has every used the Lycoming additive or an oil that contains it.

All I recall is no stuck exhausts valves.

When I joined a Jodel DR1050 (O200) Group in January 1990 it used leaded 4☆. We had a short spell on Avgas when that became unavailable, then used EN228 Unleaded until we sold her in 2020.
We once had a sticky valve.
We used Shell 15W50 except when running-in.

Last Edited by Maoraigh at 14 Jun 19:54
EGPE, United Kingdom

now where do I find UL91 stickers ? Can only find 100LL stickers online.

looking for “UL 91/94/96” placard to cover all grades.

I created my own fuel placards
using one of the online sticker companies. Here’s one in the UK. In my case I think I downloaded and used an online image of somebody else’s placard, and added my own additional fuel capacity data.

Just make them to match whatever the TC, STC or other approval specifies. They can be in your postbox in a few days. If you want stickers to last, covering them with paint protection film (PPF) is a good idea.

Last Edited by Silvaire at 14 Jun 21:04

Those who do buy UL91, do you find it’s generally more expensive than 100LL? At least in the UK I have the impression that UL91 cost about 10% more.

United Kingdom


I guess the reason for 91UL being more expensive is the lack of market penetration that results from the general level of ignorance about which aircraft can use 91UL. This is borne out by the number of people who have tried to stop me Mis-Fueling my Lycoming powered DR400 when filling the tanks with 91UL.

Things will change as both the U.K. and EU are putting more tax on leaded fuel on environmental grounds.

We buy 91UL in bulk and it is no more expensive than 100LL so I guess that some airfield owners see the main market for 91UL as the Rotax powered aircraft that are less price sensitive due to their low fuel burn , this fact also has an effect on the sales volume. Looking at one airfield’s fuel sales log I had uplifted more fuel into my DR400 than the total uplifted by the last six aircraft, as it costs the same to invoice for 190 LTS as it does for 15 LTS so cost of sales may well have an effect on the price.

A_and_C wrote:

guess the reason for 91UL being more expensive is the lack of market penetration…

That may very well be. In Sweden, where the market penetration for Hjelmco 91/96UL is high, that fuel is about €0.30 /litre cheaper (in bulk) than 100LL.

Last Edited by Airborne_Again at 06 Jul 09:30
ESKC (Uppsala/Sundbro), Sweden
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