What fuel do you run your Rotax 912S on?

[Guest basscheffers]

Looking at the various Rotax 912S durability threads, one thing that rarely comes up is what fuel people run their engines on. So time for a simple poll.

 

Please also post a reply with current hours on the engine, or any problems you have had. It will help us see if there is much of a difference depending on the fuel used.

 

 

[Guest basscheffers]

I'll start. It is now almost exclusively on PULP98 but that wasn't always the case.

 

Before I owned it, the first 200 hours were flown mostly on 100/130, without a specialised oil with pretty bad results. An unrelated failure caused the engine to be opened and on inspection, a top-end overhaul was required.

 

The next 700 hours it ran exclusively on 100LL and Shell Sport 4. No issues, but with blue fuel being withdrawn from Parafield, the last almost 100 hours has been on PULP98 from Mobil. Occasionaly, when I have not refilled the drum in time or refuel elsewhere it gets some green fuel in there, but I try to avoid it as best I can.

 

At the 800 hour gear box inspection, there were a number of parts replaced, most likely due to excessive wear because of lead use.

 

550 hours to go before TBO and as this aircraft is used for hire, it can't go on condition, so I'll have to suck it up and try not to resent those with 4000 hour engines!

 

 

[ahlocks]

197 hrs

 

BP PULP 2558 litres

 

Avgas 100LL 340 litres

 

Shell VSX4 oil & filter @ 50Hrs

 

No issues.

 

 

[Guest Maj Millard]

485 Hrs on current engine. Primarily BP prem ULP, but ocassionally will load some 100LL, probabily never more than a 50/50 mix. Previously Castrol GPS to 300 hrs, now Valvolene Durablend Synthetic blend 20w50, which I'm quite happy with. Oil changes at 50 hrs, oil and filter every 100. All good so far. Just renewed carb mount sockets due internal cracking...................Maj...

 

 

[Tracktop]

Why not include regular unleaded as well, as not all people run 95+

 

 

[ahlocks]

Tracky,

 

The Rotax manual specifies 95 ron or greater for the 912S (and 912ULS)

 

The 912 and 912UL can use regular unleaded though!

 

But you knew that. ;)

 

 

[Guest Walter Buschor]

Only done 220 hrs on new 912S. I always use premium 98 exept when away and unable to get mogas. Then use avags. Oil Shell VSX4. plugs clean as with NO residue after 100hours. no deposits on magnets.Oil change every 50 hours. Hope it will go "forever".

 

 

[bones]

1100 hrs, serviced oil and filter every 50hr +or- 2 hrs, plugs every 500hrs

 

Had to change the carb sockets, and new starter motor, thats it i think.

 

i was gonna vote 4 times but it wont let me, i run it on everythnig you got there and more, like a mix of avgas of 91 unleaded, 91unleaded, basically if you put a match to it and it burns i put in it, even had to throw a bit of kero/petrol mix in to get enough in the tank to get home.

 

No these engines are crap when you think about it :)

 

 

 

[Guest rhtrudder]

Run my 914 on straight unleaded using MXOAV. No dramas after 230 hours. Have run avgas in one tank and switched between the two, can't tell the differance. Installed a Knock meter just in case I couldn't hear the detination.Mates run their 912's on the same fuel, we all share the same tank ,engines have done 700 and 200 hours.

 

 

[bones]

Hi Bones

hehehe....almost had me going with your answer!!!

What part???

Everything was true

 

 

[Mick]

Got 280 hours on my current 912ULS, had been running it on Mobil ULP 95 until the servo I go past to get to the field changed to BP, now use their ULP 98. Of course when travelling I can usually only get 100LL at airports so that's what goes in it.

 

I run my Mogas through a serious filter before it goes in the aircraft, it does not seem to matter where you buy Mogas it nearly always has alot of crap in it.

 

Started out using Castrol GPS oil then changed to Shell VSX4. Oil & filter get changed every 50 hours.

 

 

[BigPete]

G'day Mick - are you heading to Temora?

 

regards

 

 

[ozzietriker]

use premium unleaded on 582cc, total of 432hrs - it's cheaper to use good fuel than replace your engine sooner

 

check six :thumb_up:

 

 

[HEON]

914 @ 310hr. Oil Castrol to Plus 4 to VSX. Oil and filter changed around 50hr. Fuel mogas at hanger, avgas on trips.

 

No major engine problems. Reduction gear change (no cost) SB914038. Have had air leak into RH carby at max rpm via float bowl resulting in lean mixture and thus loss of power.

 

Not an engine problem but 914 has to have ample cool air to prevent the reduction in boost automatically by engine management system if it draws a lot of warm air from within engine compartment.

 

 

[peterholmes]

hi guys

 

Im sure this fuel stuff in fairly common knowledge but I'd like to hear maj millards (lame) opinion also,

 

I have a std 912, the std 912 has a 9:1 compression ration which means it can run on 91 octane (mogas)or higher if you like , but the 912s has a 10.5:1 compression ratio, so theoretically using 91 octane will cause detonation so 95 premium is the minimum and 98 an option, anything above this is superfluous,

 

I have used 91 octane in my 912 for 320 hours no problems

 

compression ratio is linked to combustion chamber flame speed which causes detonation.

 

obviously some pilots use what is available.

 

what would be an "ideal" is a antiknock sensor, oxygen exhaust sensor with a computerised ignition advance, this would mean we could put any fuel (within reason) thru our engine and the engine would not detonate thus not destroying it over time,

 

why do most modern car engines get more performance / economy and don't detonate when using 91 or 98 octane. :thumb_up:

 

 

[Guest Maj Millard]

Yes, as noted by Peter the lower compression 80hp 912 is happy with 92 or 95, or even avgas.

 

The 100hp 912 uls, or S, which is a higher compression engine needs min 95, and preferrably 98 octane, and will also happily run on Avgas.

 

On a recent long cross country trip I ran them all in my 912ULS. The biggest problem with flying cross-country is (A) getting fuel period, and (B) getting the fuel that you like, or would normally prefer. You often have to settle for whatever you can get at the time.

 

I generally managed to run around a 50/50 avgas-95/98 mix in the tanks, but on one occasion had no choice but to load some 92, as it was all that was available. I also had to use fuel brands that I would not normally use by choice.

 

Having the Avgas in the tanks in varying quantities, helps to negate any harmfull effects the other not-recommended or preferred fuels may have.

 

My trusty 912ULS took it all in it's stride, and continued to humm along apparently not too concerned with what it had to consume, however I would not recommend using unrecommended fuel grades (in this case 92 octane) unless in small mixable quantities and only if absolutly necessary.

 

We are fortunate to be able to use engines that have this operational flexability, as it is not always the case with some other engine types..........................................Maj...

 

 

[Guest basscheffers]

You have to be careful with what you call "happily on AVGAS", though. The 912 is only supposed to run on 100LL (blue), not the 100/130 (green) crap we get here in SA and WA.

 

Even on "low lead", you have to change the oil twice as often and the gearbox inspection comes 100 hours sooner. Also don't run it below 5000 rpm; the hotter, the better it deals with lead.

 

If you must run 100/130, do it only occasionally and run the engine hot. Running it long term on 100/130 ensures you won't make it anywhere near TBO.

 

 

[Guest AVU]

When using avgas, a little bottle of upper cyl. lubrication will keep the valve stems clean and minimises carbon

 

 

[Guest disperse]

You have to be careful with what you call "happily on AVGAS", though. The 912 is only supposed to run on 100LL (blue), not the 100/130 (green) crap we get here in SA and WA.Even on "low lead", you have to change the oil twice as often and the gearbox inspection comes 100 hours sooner. Also don't run it below 5000 rpm; the hotter, the better it deals with lead.

 

If you must run 100/130, do it only occasionally and run the engine hot. Running it long term on 100/130 ensures you won't make it anywhere near TBO.

Two questions. 1) if using 91 mogas, would a octane boost additive help.

 

2) How does particular fuel affect gearbox tbo ?

 

Regards Troy

 

 

[Guest basscheffers]

1) if using 91 mogas, would a octane boost additive help.

The manual specifies 95 octane or better, no mention of mixing your own, so I wouldn't! :)

 

2) How does particular fuel affect gearbox tbo ?

The same oil that runs through the engine runs through the gearbox, so any lead that makes it into the oil also makes it into the gearbox and wears down its parts.