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The CT's sitting a lot fuel care question?

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It's been a month now since I received my new to me 2007 CTSW with 680 hours. She has been sitting in a insulated and heated to 45 degree hanger fueled with 20 gallons of 92 non ethonal mogas.

 

Question: with 3 more months of crappy weather here in Montana she will be seldom flown. What measures should I take now to guard against gumming the carbs and preserving the fuel? She's not in storage and may be flown so I need to to be ready to fly as well.

 

Thanks in advance for any recommendations!

 

Dave

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It's been a month now since I received my new to me 2007 CTSW with 680 hours. She has been sitting in a insulated and heated to 45 degree hanger fueled with 20 gallons of 92 non ethonal mogas.

 

Question: with 3 more months of crappy weather here in Montana she will be seldom flown. What measures should I take now to guard against gumming the carbs and preserving the fuel? She's not in storage and may be flown so I need to to be ready to fly as well.

 

Thanks in advance for any recommendations!

 

Dave

 

Run it once in a while on the ground.  You can use 91E10...with ethanol.  You can also switch to a full synthetic oil like Mobil 1 Motorcycle Racing Oil if you stay with Mogas.  That oil will help with higher temps during summer.

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Run it once in a while on the ground.  You can use 91E10...with ethanol.  You can also switch to a full synthetic oil like Mobil 1 Motorcycle Racing Oil if you stay with Mogas.  That oil will help with higher temps during summer.

Nothing wrong with this advice, but one point to be aware of: if you run full synthetic, you can't run 100LL at all. If you are flying away from home and can't get mogas, you will want the ability to use avgas. Most run a semi-synthetic for that reason.

 

Also, be aware that the Rotax guidance changed recently, and now the only oil Rotax recommends for all fuel types is Aeroshell Sport +4 (semi-syn). Other oils will certainly work well, but they are not the recommended oil by Rotax.

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Great tip! I will only run Shell as I plan to travel this spring and will have to use both fuels.

 

I learn every time I open this forum! It's amazing!????????

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I would recommend running that engine up to normal operating temperature (minimum 124*f) at least every 10 days. In your environment, during ground runs, that may require placing a little aluminum tape over the radiator inlet, to get the temperature up.

Frequent run ups (every 10 days) will keep the seals moist and guard against contractual seeps (water and oil). If you leave the engine sit for weeks on end, do not be surprised to see seeps here and there. Those seals and hoses need to be exercised. Dry seals invite cracking.

 

Full synthetic oil is great stuff, but I concur with Andy on oil selection, if you occasionally use 100LL.

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Great recommendation! Makes sense to reach temp for water avoidance.

 

All my nosy neighbors who live by the runway and are waiting for me to fly this rig will see me taxi out and think the Buckaroo air show is starting!????

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Great tip! I will only run Shell as I plan to travel this spring and will have to use both fuels.

 

I learn every time I open this forum! It's amazing!

 

You can run Mogas 91E10 all the time and run a full synthetic like Mobil 1 4T Motorcycle Racing oil (Rotax is not assuming you are running Mogas exclusively so recommends the Shell oil if you ever run 100LL).  You can buy Mobil 1 4T at any Walmart or auto store.   https://mobiloil.com/en/motor-oils/mobil-1/mobil-1-4t-motorcycle-oil

 

When away from home, you can use Decalin TCP  which scavenges the lead from the Avgas and maintain the full synthetic status.  https://www.aircraftspruce.com/pages/ep/fueladditives/Decalin.php   I put a small amount in a glass baby bottle to take on trips and only needed to use it about three times.  Very little is used for a full wing tankful, about a teaspoonful.

 

I ran this in my CT for over two years and it was a big win.  The engine ran cooler and the gas was cheaper.  But to do that I had to make my own fuel trailer.  When I sold the plane the new owner wanted to keep that status so he also bought the fuel trailer and is also running Mobil 1 now.  Also when you run Mogas you can delay your oil changes to 50 hours.  And you can delay the major service on your prop reduction drive gear box too by not using 100LL.

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If it is going to sit very long I would drain the auto fuel and put a little 100LL in it. Run it a litte to make sure the 100LL gets all the way to the carbs. The auto fuels are blended seasonally, where 100LL is consistent year round. If you want to fly add fuel and go.

Something else, is that the composite tanks don't sweat like the old metal tanks, so keeping them full of fuel is not as important.

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I'm thinking that over the next few months with just a few flights until Spring I'll refuel her with 100 LL. That way she can sit happy with no issue fuel until the flying season and the run her on Mogas!

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I have let mine sit as much as 2.5 months in a heated hangar with no apparent problems. Since I was physically gone the engine was not started during this time. Numerous times I have left it for 4-5 weeks.

 

I don't like doing this but sometimes you have no good choices. 

 

When I leave it I either use Stabil or a mixture of 100LL with non ethanol mogas. Since there are several sources of non ethanol mogas in this area this engine has never tasted E10 or E15. I would not feel comfortable if there was ethanol in the fuel when leaving it like this.

 

Anyway, no problems in nearly 10 years. This reminds me, my second hose change is coming up and shortly thereafter a BRS service will be due. At this rate I'll never get the RV-12 built!

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I'm with Tom. For long storage times running the engine occasionally is good, but does nothing for the fuel. Running the engine occasionally will help keep fresher fuel in the carbs. Drain the fuel and just put in 3-4 gal. of 100LL in each side. Come warmer weather time just top off with your auto fuel. If you stick with AeroShell which is a 10-40W semi-synthetic you never have to worry about oils. Since we change oil frequently either type oil is just fine.

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Decalin is highly recommended when using 100LL, but with one caveat:  It's not a magic bullet.  While it does scavenge lead from the fuel, it does not do so completely, and you will still get some buildup in your gearbox, on valves, etc.  Also, more lead makes it to your exhaust when you use Decalin, which then build up in your exhaust pipes.  This can cause changes to heat resilience, and over long periods can cause cracks in exhaust components.

 

It's best to avoid 100LL fuel whenever you can, but when traveling away from airports with easy mogas access, using Decalin is a good idea.  Just don't assume there is any free lunch on lead mitigation.

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Use 91 )ct for every day flights. Use 100LL if you plan on a long storage. 100LL is far more stable over long periods of storage time.

 

Agree, I didn't mean my remarks to be about storage if anybody took it that way, just day-to-day flying.

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 "If you flew regularly and/or used 100LL over 30% of the time, I would go with the full synthetic."

 

Isn't semi-synthetic recommended when 100LL is used over 30% of the time?

 

Also, is the fuel preservative - Stabil - ok in the CT?

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Stabil or Seafoam helps, but isn't a cure all. Remember the engine must be run long enough AFTER you pour these into the tank to get it throughout the system and especially into the carbs.

 

It's still a good idea to use 100LL in a tank for long down times.

 

Semi synthetic is for all fuels and a full synthetic is only for unleaded auto fuel.  Aero Shell Sport Plus 4 is a 10-40W semi synth.

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Is there any opinion about running the 912 until it stops after shutting the fuel valve?  That would get most of the fuel out of the carbs and reduce the problem of "varnish" (dried fuel residue) affecting carbs during long-term storage.

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Anything over 2 months. Sitting fuel will lose additives and octane and can start to clog that tiny hole in the idle jet. Iyt usually takes longer, but testing the exact time table means you may be removing a carb to clean the idle jet. I have one such case on a 701 due in here tomorrow. It did sit a lot longer than that though. If you can go out twice a month and start it up and get to operational temp. That at least gets some newer fuel in the carbs and system.

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Yes but what about the issues of the engine never getting up to 200 degrees or so to steam off water condensation?

 

I used to go out and run my Harley 5 minutes or so in the winter and soon found my oil milky white. I stopped that practice.

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Is there any opinion about running the 912 until it stops after shutting the fuel valve?  That would get most of the fuel out of the carbs and reduce the problem of "varnish" (dried fuel residue) affecting carbs during long-term storage.

 

I am not certain, but I would venture a guess that even with the fuel off and the engine stopping there would still be some fuel left in the carburetor. The small amounts are sure to dry up and turn to varnish much quicker, only to flake off and cause problems when put back in service. This applies to auto fuel, I have never seen an issue with 100LL sitting for extended periods. I will give you 2 examples that I am aware of, but not Rotax related.

 

One is a Piper J-4 Cub Coupe. It sat for a couple years with auto fuel in the tank and carburetor. It wouldn't start when they pulled it out of the hangar. The carb had to be disassembled and cleaned. The fuel lines had to be replaced, and the tank removed and steam cleaned.

 

The second was an Aero Commander 100. It sat for 4 and 1/2 years with 100LL in the tanks. The airplane was pulled out of the hangar, a new battery installed. The engine started and ran almost as soon as they started to crank it over. There were no fuel based issues.

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I have let mine sit as much as 2.5 months in a heated hangar with no apparent problems. Since I was physically gone the engine was not started during this time. Numerous times I have left it for 4-5 weeks.

 

I don't like doing this but sometimes you have no good choices. 

 

When I leave it I either use Stabil or a mixture of 100LL with non ethanol mogas. Since there are several sources of non ethanol mogas in this area this engine has never tasted E10 or E15. I would not feel comfortable if there was ethanol in the fuel when leaving it like this.

 

Anyway, no problems in nearly 10 years. This reminds me, my second hose change is coming up and shortly thereafter a BRS service will be due. At this rate I'll never get the RV-12 built!

 

Stabil is a no-no for fuel in a car with a catalytic converter so we never used it in the plane just in case there was something there that might be affected. 

 

Mixing 100LL and Mogas is okay.  The only real issue for Mogas (ethanol or not) is a hot day at high density altitude it is possible to get vapor lock...but there is no danger regarding water (unless you park it in the rain outside) or stale-ness.    Like most things, nothing is totally free.   It is true that a full syn oil like Mobil 1  4T motorcycle racing oil is optimal for the Rotax.  But can only be used if you do not use 100LL (or if you do, use Decalin to scavenge the lead).

 

We used Mogas 91E10 exclusively in the plane for over two years.  This allows doubling the interval between oil changes and is better for the engine in general.  We often had gas sitting in the fuel trailer for months at a time and it worked fine.

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I think I'll be good! My seller flew the plane out a month ago and refueled 1/2 way from NM with 100ll. When he arrived we put 10 gallons of Mogas in and we flew her a bit. Now she's sitting in a semi heated hanger and 50 degrees.

 

I just fueled my 30 gallon Handy tank with 10 gallons of AG that the plane was given 10 gallons from that was full of Mogas.

 

So now the plane and my Handy tank will be sitting for three months until the ice breaks.

 

I guess the point is both tanks will have approximately a 50/50 ratio of Mogas and 100 ll.

 

Friday it will be -13 below zero! Please everyone do not move here or visit Montana it's a scary place! ????

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