Avgas viz Mogas

walnut · Post by **walnut** » Mon Aug 02, 2010 10:37 pm

Having just finished a Jabiru 430 I am now awaiting the P to F.
So now I switch my thoughts to operational matters.

The engine is a Jab 3300A no 978. So I believe it is the low compression model and has the modified carb needles.

So as I see it, the engine is certificated to run on either Avgas LL or Mogas 95 or higher. But there seems to be a conflict, Mogas is a cleaner fuel but loses its octane rating with time, thus causing pinking; whereas Avgas LL avoids the pinking but leaves a lead deposit which causes the head to become contaminated?

I appreciate Mogas is cheaper but this is small beer compared to the cost of an early engine overhaul or even long term damage.

So should I alternate fill ups between the two fuels or should I go for the higher octane unleaded fuel 98+ which to some extent will take longer to degrade below the minimum 95 allowed.?

I am also aware that alcohol is now being added to Mogas, 10% seems to be the limit, but how do I test for its presence?

Any thoughts please?

John F

Nick Allen · Post by **Nick Allen** » Mon Aug 02, 2010 11:07 pm

I am also aware that alcohol is now being added to Mogas, 10% seems to be the limit, but how do I test for its presence?

Use one of the tester kits available: there's a link on the Engineering page to Airworld's website, from where such things can be purchased:
http://www.lightaircraftassociation.co. ... _main.html