Hi guys...
Just had a general query ...
I've heard a lot and seen a lot ... so i just need some more opinions / experiences
What is the lifespan of a nitro engine ... specifically, race competition engines ... .12 and .21
Ive heard of instances where engines are needed to be rebuilt after every race meet ... ive heard of instances where an engine (unopened) has been used for a whole year worth of race meets without any issues whatsoever ...
Another "fact" that i have heard is ... the use of specific fuels will determine the 'lifespan' of a motor ...
For instance .. .12 motors using 15-16% nitro fuel ...
A motor using a fuel with say for example 11% oils [Nitro X - they dont list how much % syn and castor oil is in it, just a total figure of 11% oils] has far less lifespan than say the same motor using another fuel with 20% oils [Hot Stuff - they state it has 15% syn oil and 5% castor oil] - Apparently, genearlly the motor running the fuel with less oils has around 30L of fuel life before a rebuild is required as opposed to the motor running the fuel with more oils has 80L if not more no sweat of fuel life before a rebuild is required ...
The apparent logic / reasoning behind this is because the fuel with more oil in it lubricates the engine, whereas the fuel with less oils in it doesnt lubricate the engine at all, or has very little lubrication for the engine, and therefore, has a lower life span, up to half that of the engine running the fuel with more oils in it.
Also, the fuel with less oils in it, makes the engine work harder and produces more performance ... lets say for example / figures sake, the fuel with less oil allows 95% potential to be reached .... than the fuel with more oil allows only about 90% potential to be reached ... again life span is decreased accordingly.

Also, it is believed that the fuel with less oils, overtime, about after 1L of fuel, the engine has a build up of 'gunk' on the internal surfaces and hence makes starting and tuning a biatch ... as opposed to the fuel with more oil, leaves no build up at all and hence starting and tuning is a breeze .....

Experiences and opinions?

Cheers guys

You can never tell.....

Factories are changing materials constantly and the quality and ofcourse with it. The running in proces and when starting up the warmup proces is very important for the lifespan. Oil is also important, a drop more can do a lot but will also take away the driving time on 1 tank, thats why most high end fuels have 8~9% oil. Also fuels are changing, you will never know what you will get next time and sometimes there is a batch damaging the engine....

Gearing wil help.... large gearing gives less top rpm saving the engine but it can give more stress on the internal parts, for sure the rod. A light gearing will give more RPM and also more stress (higher G-forces at a high rpm) and the higher rpm can give loss in the lubrication, you need to find a middle way. So going for maximum performance will always affect the lifespan.

in my expirience, 5 to 8 races ... after that, loss of power. After that, idling problem.

Speaking competitively, 5 races only.

this question depends on application and how you are tuning
I ran a .28 sport engine for 2 race seasons before the crank bearing gave out.
Always want to see smoke and don't run the engine too lean
I have had the same engine in my Losi LST which is a 427 Mach ported and polished for more then 4 years now.
About 3.5 gallons or more and it still runs strong
I have been using Odonnells 20 or 30 %
this fuel has always been my choice I have tried a bunch of others but never had any luck
also always keep the air filter fresh

In regards to coments of castor synthetic in nitro fuel blend/contents. It does leave a residue on sleeve liner and piston surfaces ,that will of course vary the many blend out there. My observations are with the 100 plus piston and sleeve sets received here each month for reconditioning-resizing services. Of course this residue (to an extent) is the necessary protection, but will also be misleading (when engine cold) the piston + sleeve sealing capabilities effecting engine compression (power) when at operating temp. From the racers end he will see this power loss (especially coming out of corners) and also very noticable change in ideling capabilities. From my end , the removal of this film/residue is essential so as I can reform/restructure sleeve bore + piston (an accurate new designed fit) to suite a nicely "matched" piston and sleeve set. its intriguing when I first pull a piston + sleeve set out of package for inspection and prep as to how normal felt seal with residue still adhered to surfaces, becomes nil / unexceptionable fallowing first clean up. It veries, I see many sets after just a few gallons from onroasd guys( I used to race onroad myself now race offroad) while the offroaders will go (in my opinion with observations) will run much longer before freshining up the seal for optimum performance. Again , as was mentioned a previous post here, it depends on an engines application and racer needs. Bottom line , with the cost of all these little 2cycle nitro engines we want to get the best engine life possible/available to us. Preventative maintenance with a high level care is essential these high maintenance engines. The other alternative is getting caught up in the engine hype and purchasing new engine more often. I personaly can be concidered more compulsive with bearing changes than resizing my own engines. RayAracing

So, cleaning up this residue(brownish carbon) improves the performance of the engine? Sorry, I dont have a good English...

My engines perform exactly as you said. They run absolutely in top condition after breakin, but as the carbon builds up, they lose their "liveliness". But does cleaning up those residue brings the performance back, or makes it worse?

No, Absolutely not. You remove this build up on a piston and sleeve set running marginally, you will be increasings piston to sleeve bore clearance, making things worse. Again, I only clean these surfaces allowing me to match worn piston to newel y resized sleeve bore. Not to elaborate too much here, but this prepping procedure is one that simply allows me a clean surface to adjust ( reconstructing smaller bore a few tenths of one thousandth one inch) new fit to. It would be very the manufacturer to match piston + sleeve sets working with dirty surfaces. I hope this helps. RayAracing

is this with the fuel that has 8-9% oils?

To be honest, i run my engines a little on the rich side just to be safe ... however my performance is compromised ... so running a tad on the rich side as well as running a fuel with more % oils, thats a double negative on performance for me
I am running a .12 OS Speed 12XZ and a .12 OS TZ
I notice that my bottom end is nothing compared to other guys running less oil, however top end, its not that far off ... so if anything i have to accelerate mid-way through a corner to make sure i build up exit speed to try and keep up with the boys running the fuel with less oils in it
But i do notice that with my engine and fuel combo, i barely have to touch the tune ... and after a large bottle of fuel, one of the racers inspected the engine, compression, and looked down the plug hole and said it still looks and feels like a virgin
In comparison, the other guys running fuels with less oils in them, they have to constantly tune their motors due to starting issues, or running issues ... and also, i notice them with new motors every so often while im still on my first motor

Thanks for that input Ray ... so in keeping with the best engine life possible motto, do you recommend to run a fuel with more % oils in it?