Hi there; i have a few 4 stroke engines brand new, saitos, os, and magnum; i will start using them shortly; so this is the question:
I will start with a magnum 52 4 stroke blue head; wich is the best fuel recomended for performance and durability?
Any real diference beetween 2 stroke and 4 stroke fuel?
Can you use 2 stroke fuel in 4 stroke engines?
Thanks in advance for your answers.

Hi!
I mix my own fuel since I started flying R/C och CL 36 years ago. I use 15% all synthetic oil (Aerosynth 2 , Aerosave and Motul "Micro") and 5% nitro for all my engines, both two and four-strokes, except for my small COX engines that run best with some Castor oil and 25-30% nitro.
But as you live in the US and perhaps have no retailer that sell those modern synthetic oils its best for you to buy ready mixed fuel. There are several manufacturers: Powermaster, SIG, Morgan for just naming a few.

16%-20% oil, either Castor or synthetic or a blend is what is mostly sold in the US. 15% nitro is the norm at your place, but 5% nitro is all it takes to have all (except perhaps Y&S four-strokes) engines to run just fine.

Remember ! There is no special fuel for either two or four strokes! These engiens can be run on the same fuel as long as the oil content is around 15%-20%.
Two and four stroke oil/fuel is something that was "invented" by some fuel manufacturers decades ago and mean nothing today and meant nothing then!

Ignore marketing terms like 'two stroke' or 'four stroke' and concentrate on the oil type and percentage.

The owners manuals have a fuel recommendation. Makers of most modern four stroke engines recommend 18 to 20 percent oil. Magnum specifically recommends using some castor oil. OS and Saito say castor is optional.

Some castor always helps to provide the heat protection that synthetics can't give.

SIGChampion 15% nitro. Works great in both 2 and 4 strokes, has 50/50 synthetic / castor blend and a total of 20% oil. Iuse it in ball bearing and bushing engines as well as all my 4 strokes.

Good old "Omega" type fuel, 15% nitro, 18% total oil of which a small percentage is castor is what I run in all of my engines, 2 and 4 stroke. Some folks who want every last rpm out of their engines and don't care about cost will run higher nitro percentages though.

Ernie Misner

I did some tests last summer with 5% nitro, 10% nitro and 15% nitro. I used a temp gauge for reference between the three fuels, and noted the rpm differences. I'll have to see if I have the notebook around with all the stats to post up. I can say that I only noted 200rpm gains for every 5% nitro I added, so from 5% to 15% only gave me 400rpm more. If I needed that extra 400rpm and didnt mind the engine ran hotter, I'd run 15% all the time. But I dont. 5% nitro and all castor (its cheap) 20-25% depending on the engine is all I use and it works well for me.

Castor might make the ring stick in ringed engines, but only if left to sit for a long time. I would use at least 5% castor (of the total oil content) in any engine for the rust and overheat protection.

"4-stroke fuel" is a gimmick. Not any different than telling someone "gullible" is written on the ceiling and they look up.

+1

Bruce

Last time I looked, the "4-stroke" fuel had a lower percentage of lubrication. I have always used Omega fuel for both my 2 and 4 stroke engines, and like the performance and longevity. I have used 15%, but found I did not need the extra nitro, and now use 10%. Some engines (magnum and Supertigre) seem to perform best with 10% maximum nitro. Saito will benefit from higher nitro content, but don't need it to run well. YS engines require 20% nitro with 20% synthetic oil content.

I hope the YS's don't absolutely have to have 20% nitro unless you need max power. I have a new YS 70 and we'll see how it does on the good ol' Omega 15% .....

Ernie

I`ll be fine, thrust me. A friend of mine has never ran his YS 63-S on anything other than 15/15 synth and it is a very capable and impressive engine still, blows everything in the same size away despite only 15% nitro

Myself, I have ran my YS engines on anything from 0% (FAI) to 60%, but I have found that my standard 15% is fine for me. My 110 actually ran fine and flew great on 0% after alot of tweaking the needles and regulator, but I didn`t tach it that time so I can`t comment of how much power was lost, I regret that now

Out of six popular brands that have a fuel described as 'four stroke,' I only found one with an oil percentage that I would consider too low for my engines. That's why you need to check the ingredients instead of the marketing terms.

These are fuel brands that I have actually used. I did not attempt to find the percentages for every brand that exists.

Powermaster - 14%

Cool Power - 17%
Omega has 17%
Ritch's Brew - 17%
Magnum - 18%
Wildcat - 18%

I would not use Powermaster 'four stroke' fuel in anything I own but their regular fuel worked well in my engines.

IME, Saitos do better W/O castor.

I have had my best long term (Saito) performance W/15% Morgan's Cool power.(full synthetic)

I used Morgan's Omega (synthetic/castor mix) @ first in my Saito FA 150 & started noticing a cracking noise when the engine was turned over by hand when cold. It turned out to be the exhaust valve sticking to the seat & the "crack" was the adhesion being broken.

I later had to replace the cam as the exhaust lobe had excessive wear.

Saito also recommends avoiding castor oil in the fuel.

>>> I later had to replace the cam as the exhaust lobe had excessive wear. >>>

This seems to happen more when there's no castor in the mix. Go figure.

Thanks,

Ernie

They recommend against using fuel with all castor oil.

Big difference between a little castor and all castor in terms of mess, goo, and carbon. Although a few still do run all castor, it mostly went out with the advent of quality synthethics. The mystery about European synthetics being so much better than ours is still alive and well.

The smell just isn't the same anymore though. Does anyone remember the smell of the hot Thimble Drome fuel in the red pint size cans? The tame stuff in the blue can wasn't so bad either. Talk about "smelling like the races!".

Ernie Misner

While not an absolute, I would use all synthetic lube fuels in the YS to keep from gumming up the works.  Otherwise, I always have some Castor in the mix.  And I would bring Omega up to 20% total lube by adding some Castor to the mix.  My old Saito and Magnum engine manuals both recommend the use of 20% lube.  Magnum as previously mentioned also recommends some Castor.  Maybe someday we will have those superior synthetic oils used in Europe but until then I always add Castor to the mix except for the YS.

I add castor to Omega fuel too. The synthetic oils being mentioned still won't stand up to heat like castor. I've not seen anything that states they don't burn to ash.

Thanks everybody for your inputs and sugestions.
this is the fuel im using:
manufacturer: morgan fuel
says on the bottle: omega 5% f-om-5, castor/syntetic model engine fuel

according the tag on the bottle; what are the content or characteristics of this fuel?
what 5% means that? what is the amount of blend content?
is this fuel good for 4 stroke engines?
should i add something extra to this fuel? if yes, what?
thanks again.

That's 5% nitro and 17% oil (30% Castor/70%synthetic) . It'll work, but it's not my first choice. 15% nitro may give you a bit lower and more reliable idle and a tad more power.

Castor seems to run towards the heat and when it does, it helps lube friction trouble spots. It also helps protect bearings during storage. The down side is, it can burn or "coke", a tar like goo that can stick rings or valves. My opinion is that I'd like to see a small amount of Castor and the majority of the oil synthetic for ring engines.

A little off topic, sorry, but with the YS engines the only reason not to run a little castor is the diaphram in the regulator, right? The cam, lifters, and rest of the engine could benefit from the castor just like a Saito or OS 4-stroke it seems like. We run castor in the perry and other pumps and regulators. I'm going to try the bit of castor in my YS 70 but not let any sit in the diaphram over the winter..... and see how that works....

Ernie Misner