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Risk of use of full synthetic oil with 100 LL

in 912 / 914 Technical Questions 11 years ago
Hello,

In a few days, I will proceed to my first 100h visit for my 912UL. I bought my microlight end of june 2012 and the engine had 128 h. Now, it's near to 221 h.

For the lubrication, I use semi-synthetic oil Yacco AVX 4T 10W40, since I have to fill sometimes the fuel tank with 100LL (on airports where there is nothing else than that), even if the total amount of 100LL remains less than 15% of fuel consumption.

The mecanician that will do the 100 h visit strongly advise me to skip the Yacco and go for Castrol Power 1 4T 10W50.

First of all, I'm not pretty happy with that, since SI-912-016R5 mentions that this oil is not anymore recommended by Rotax. I know some people that use this oil (for many hundreds of hours on different 912) and never had any troubles with it. Does anybody have bad experience with that oil?

Secondly, this Castrol Power 1 is 100% synthetic. What are the main problems that could occur when AVGAS100LL is used (let's say up to 20% from total fuel consumption) in combination with the Castrol Power 1?

Thanks for your independantly return of experience and advises.

Best regards
EF

  • Re: Risk of use of full synthetic oil with 100 LL

    by » 11 years ago

    Hi Eric,

    I will admit I don't know a lot about this Castrol oil because we don't have it here and I haven't ever use Yacco either. If you use 100LL you should stay with the semi synthetic. A full synthetic will not suspend the lead and it will fall out of the oil in places you don't want it and it won't drain with the oil on a change. It's your engine and I think that mechanic may need to do some reading on semi and full synthetic oils and how they work in 100LL and the Rotax. If you use unleaded auto fuel then either type oil will work just fine. I'm with you and I don't think I would use Castrol oil in my 912. It could be okay I just don't know? How hard is it for you to order Aero Shell Sport Plus 4 semi synthetic? It is Mfg in the UK so you are only a stone's throw away. That would solve all your debates.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Eric Fourchault
      
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  • Re: Risk of use of full synthetic oil with 100 LL

    by » 11 years ago

    Hello Roger,

    meanwhile, the mechanic (who has a very good reputation) agreed fully that semi synthetic has to be used. He didn't read properly the few words I made to him explaining the history of my engine and the way I use it, indeed the non negliegeble quantity of 100LL I use). But he strongly suggest me to use a 15W50 oil, arguing that the higher viscosity of such oil grade at higher temperature will help the lubrication to be effcient, especially on the gear pignons. Since I'm not a specialist but understood more or less his explanation, I followed his advise. In the SI-912-016R5, I found the oil Shell Advance VSX4 15W50 and got it in Germany online for good price.

    Will see how good it works. Hope not to bad, since I fly often over the mediterranean see from France to Corsica ;-).

    Best regards
    EF
      
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  • Re: Risk of use of full synthetic oil with 100 LL

    by » 11 years ago

    Mobile had a pure synthetic aircraft oil and in the early 1990s spent hundreds of millions of dollars to rebuild customers engines and later pulled their aircraft oil off the market. Pure synthetic oil will not hold dirt, carbon or lead in suspension. That forms sludge and ruins engines. Shell, Exxon and others sell semi synthetic (about half synthetic and half mineral}because the mineral oil holds the bad stuff in suspension and it goes out of the engine when you drain the oil.
      
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  • Re: Risk of use of full synthetic oil with 100 LL

    by » 11 years ago

    Question for Roger Lee ...

    As I understand it, in using Decalin, the lead is purportedly "suspended" in the oil and drains out with the oil change. Is the suspended lead actually visible (can it be distinguished by its color and/or texture from the oil)?

    Thanks for your time.
      
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  • Re: Risk of use of full synthetic oil with 100 LL

    by » 11 years ago

    Hi Dale,

    The Decalin is for the fuel leading with 100LL use. The oil needs to be a semi synthetic or a full mineral based oil to suspend the lead. A full synthetic won't suspend the lead and it will fall out of solution to places you don't want it. You should be using at least a semi synthetic oil in your engine when using 100LL and if you use auto fuel all the time you could use a full synthetic. Semi synthetic works for both fuels. Don't use a straight mineral oil. The semi synthetic or full synthetic can hold up to the rigors the engine demands of it better.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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