100LL AVGAS or Mogas?

sp2b · Post by **sp2b** » Sun Aug 24, 2008 9:03 pm

Greetings to all,

So here I am training in a rotax powered LSA (912 rotax --100 hp) and this question popped into my mind.

Since the LSA I fly currently uses mogas, what happens when I finally do my x/c? Specifically, most of the FBOs sell only 100LL and not mogas here in southern CA. Do I fly around with a gas can and after I land I run to a gas station?

I know that generally you can use the next highest grade (i.e. 100LL) if mogas is unavailable, but is this safe for the engine?

Thanks

CTflyer · Post by **CTflyer** » Mon Aug 25, 2008 4:55 am

Seems like a good question for your cfi!

What does he/she say about re-fueling on the x/c flight?

Your FBO or flight school would probably have some heavy restrictions on the use of a rental plane, including fuel. If you own the plane, I sure hope the engine manual talks about approved fuels that won't void the warranty.

Edit: on a solo x/c, you may have to carry a can of gas in the right seat ... but your dual x/c would give your cfi a chance to advise on fuel purchases.

Tom

Jeff Tipton · Post by **Jeff Tipton** » Mon Aug 25, 2008 4:29 pm

Generally the 100-LL can be used in the Rotax 912 and 914 series.

The main concern is the clutch in the reduction unit becoming contaminated with lead from the fuel, resulting in the clutch slipping. you would notice a higher RPM on takeoff but a reduced rate of climb.

A steady continuous diet would probably require the gearbox to be removed and repaired around mid time. The eighty horse units typically do not have the clutch.

If the engine is running with synthetic oil this will be a larger concern as the lead will not stay in suspension the same as it would with petroleum based oils, which would lead to sludge buildup.

I would not be a big fan of carrying fuel in a container in the aircraft with me. If we were to crash, the container would probably rupture. And let's not forget about the potential fumes while enroute..

sp2b · Post by **sp2b** » Tue Aug 26, 2008 3:34 pm

I appreciate all of the helpful information in your responses CT, and Jeff.

I will follow your advice and will first ask my CFI. Notwithstanding, I will of course abide by the maxim of "safety first".

Thanks.

tadel001 · Post by **tadel001** » Tue Aug 26, 2008 4:36 pm

We fly with 100ll always. We have mixed before. You can mix without a problem. We have engines with 500-800 without any signs of problems.

CharlieTango · Post by **CharlieTango** » Tue Aug 26, 2008 5:08 pm

how far is your x-country flight? what is the range of the SLSA?

i fly up to 500nm round trip without refueling so that i can use the mogas in my hangar.

i only have to deal with avgas on rare occasions ( long trips )

if you want to make mammoth lakes a stop on your x-country i'll fill you up

for that matter i think there is a stop enroute to vegas from LA that sells mogas.

rfane · Post by **rfane** » Tue Aug 26, 2008 10:37 pm

Ed,

Can I get some free gas if I come by?

I don't think any CFI is going to sign him off to venture up to your airport! Maybe for a Mountain Flying checkout.

sp2b,

The Rotax engine is designed to burn 91+ Octane MoGas. It will also burn 100LL just fine, although the lead is not good for it, as has been stated. If 100LL is used, they should be using a semi-synthetic oil in order to suspend the lead, and the oil should be changed more often. A full synthetic oil will not carry the lead back to the oil filter, and it will deposit it in the engine and gear box, and can lead to a nasty lead paste (sludge) clogging the oil return channels. Many of us that need to use 100LL also use TCP or Decalin to helpo scavenge the lead, although you should consult with the school before doing so.

What fuels the plane can use should be in the POH of the airplane, and the plane should be placarded as well.

CharlieTango · Post by **CharlieTango** » Wed Aug 27, 2008 9:05 am

rfane wrote:Ed,

Can I get some free gas if I come by? ...

come by anytime roger, but i think you sneaked the word "free" in there

rfane · Post by **rfane** » Wed Aug 27, 2008 11:19 am

CharlieTango wrote:come by anytime roger, but i think you sneaked the word "free" in there

Can't sneak anything past you! Have they reopened Mammoth? I may get up your way soon, and would combine it with a tour over Yosemite. Hope you and Erin are well.

sp2b · Post by **sp2b** » Thu Aug 28, 2008 3:31 pm

CT, Rfane et al,

Thank you for responding.

As for clarification, I Previously flew a CZAW SportCruiser (awesome plane), I currently train in a SkyArrow tandem. It has a pusher prop Rotax with a Dynon EFIS (D-TEK) and Garmin 496 w/XM weather (although the instructor will not permit me to use it, since he wants me to master the art of pilotage-- and I agree with him).

Notwithstanding, I guess I am a little paranoid being that I have a 15 gallon tank, with a 6 gph burn rate; more than enough for the SP X/C requirements. Just wondering what to do if I ever rent the plane to take some long X/C's from say KSMO --> KVGT (appx. 212 nm).

Live and Learn!

CharlieTango · Post by **CharlieTango** » Thu Aug 28, 2008 3:50 pm

sp2b wrote:...Just wondering what to do if I ever rent the plane to take some long X/C's from say KSMO --> KVGT (appx. 212 nm)...

it depends on the plane and the owner. this is an area where the owner has discretion. if i owned a SLSA rental with a 912 i would prefer mogas to keep lead accumulation minimized but i would use blended oil to better suspend the lead, knowing that you would likely top off in north las vegas with avgas.

in some designs like ctsw and ctls you have 7 hours of fuel at good speed, if there was mogas in santa monica i would do the round trip in my ctsw and get back home with 3-4 hours reserve.