2 stroke fuel in a 4 stroke glow engine? - RC Groups
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Feb 14, 2012, 08:18 PM
Buildin' fool
Twinwarbirdflier's Avatar

2 stroke fuel in a 4 stroke glow engine?

I'm sure this has been asked many times before, but can/should you run 2 stroke glow fuel in a four stroke glow engine? I have a Saito 180 black knight that I recently had rebuilt. I had just a small amount of 4s fuel to finish up last season (Magnum 15% 4 cycle) but I have a few gallons of Omega 10% 2 cycle ready for this season.

Can I run the 10% two cycle in the Saito, or will it hurt her? If it's not such a good idea, Then I need to get my order in for this season.

thanks in advance for the help Guys!
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Feb 14, 2012, 08:58 PM
H&H Hobbies
H&H's Avatar
You will have no problem . I run the same fuel in all my engines. Byron 10 or 15% Nitro - 18% oil
Feb 15, 2012, 03:46 AM
Registered User
I agree. I've always used the same fuel in my 2-stroke and 4-stroke OS engines. It was Model Technics Duraglo 10% mix with synthetic oil http://www.modeltechnics.com/glowfuel/duraglo.html. Too much castor can gum up the valves on a 4-stroke.
Feb 15, 2012, 06:11 AM
Registered User
Twinwarbirdflier you can use the same fuel for both kind of engines HOWEVER keep in mind that you should ALWAYS stay with what manufacturers advice you to do. That's because manufacturers test they're product to the max and know what does better for the engine.
Feb 15, 2012, 06:55 AM
Registered User
You can run glow fuel in your 4 stroke the 2 stroke/4 stroke fuel is BS
Feb 15, 2012, 07:50 AM
ARFs Are Me
TomCrump's Avatar
Twin, I run 2 stroke fuel in all of my four strokes. You may find, however, that your big Saito will prefer 15%, instead of 10%.
Feb 15, 2012, 10:28 AM
Registered User
Oberst's Avatar
I agee with averyone, you can run 10% and I know a few that do. Me personally out of habit I only run 15% in my 4-strokes, 10% in my 2-strokes out of habit and from what the manufacture recommends it in the manual.

As a retired small engine tech, I try not to take chances and to think I know more than the manufacture. It's safer, I believe to have the attitude I have even though- it might empty my wallet quicker.

It's one of those things I'm very superstitious about. Maybe if I were forced to try it myself, I'd have to spin around 3x's and brush my sleeves at the same time, and hope everything is OK not worrying I'm slowely damaging my engine.

That's my take on it.

Feb 15, 2012, 07:40 PM
Registered User
DGrant's Avatar
I use 15% 2-stroke fuel in all my glow engines.. 2-stroke and 4-stroke. No problems in years... really no problems ever.
Feb 16, 2012, 01:01 AM
Suspended Account

2 strole fuel ? ? ?

I never heard of 2 stroke and 4 stroke fuel till I read this thread and I am not just arriving in this hobby.

I have been using engines running on glow fuel since the 1950s.

I use 10% nitro because it help stabilize the idle rpms.
At least I think so. What the nitro does is that it carries some oxygen with the fuel into the cylinder(s).

Many carburetors have difficulty maintaining a proper fuel air ratio at low fuel flows. The nitro helps adequate oxygen in the firing chamber at low rpm.

Same fuel is used in the 2 stroke and 4 stroke engines

Feb 16, 2012, 01:24 AM
Registered User
Toysrme's Avatar
"2 stroke" and "4 stroke" fuel simply denote a change in the oil content from the maker.
its been a few years since i bought omega's 4 stroke fuel so PLEASE don't quote me on this. like its the bible.
practically all off the shelf "2 stroke fuels" are 17%+ regular old castor oils up to the old 20% number. (in more recent years this has come down as many are using base castor / synthetic castor blends, or selling "premium" fuels to price gouge & be synthetic castor)

practically all "4 stroke" fuels i recall coming across in the US contains:
15% nitro
17% oil (first common down from the typical 20% oil)
AND the coil is a castor / synthetic caster blend, or a full synthetic castor oil
NOT straight old fashion low grade "castor" oil

the 4-stroke fuels came about with the lower oil content & synthetic castor oils before 2-stroke fuels common today.

this is also why Klotz fuel was so popular with older 4-stroke engine buyers. it's a good quality, relatively cheap synthetic castor oil & MANY MANY MANY pre "synthetic" flyers staunchly believe in 20% oil regardless of anything. So SIG sold a TON of Klotz to the old buggers that want that 20% oil number back. (and people mixing their own fuels)

where the reality in LARGE engines is that provided the oil is up to it you can run well under the normal 17/20% oil "standards". 5% was not completely unheard of long ago in the 30cc+ engines (i personally wouldn't trust mine to it). 10% synthetic has been gaining popularity for all engines in the last few years as a custom blend for sport engines.
decreasing oil decreases the cost of the fuel, increases flight times & (like high nitro) can increase engine performance. tho on normal off the shelf engines, or small engines, just like real high nitro contents most of the benefit is placebo & little to no change in top performance will be measured.
Last edited by Toysrme; Feb 16, 2012 at 01:37 AM.
Feb 16, 2012, 04:30 AM
Registered User
Just check the oil content in the fuel, and what the manufacturers recommend for their engines and it will be fine.
Some 4 stroke fuels have a lower oil content than than required for the engine.
I have run 2 stroke fuel in all my masses of 2 and 4 stroke engines for over 30 years, no after run oil, and not a problem,
I have two OS 4 strokes that are over 25 years old still running well today on 2st fuel (byron 10% sport).
My Saito 1.80 I run on Byron 20/20 YS mix and it runs superb.
Choke the engine by finger over exhaust method, get a stick and just lightest of taps on the prop against rotation and it purrs into life, everytime.
I run my engines in up to 50c and 100% humidity with no adverse affects at all.

(from Dubai)
Feb 16, 2012, 06:04 PM
Registered User
The PIPE's Avatar

Clarence Lee used to be "the guru" for LOWER oil percentages in 4-stroke fuel....

Dear Fellow FOUR STROKE Lovers:

The PIPE Here...I've seen a good many of Clarence Lee's reviews of four-stroke mills from the pages of the now-defunct RC Modeler magazine here in the USA, and that's in addition to having my own volume of the RCM-published, very late 1980s-era four stroke engine book he authored.

In a LOT of those engine reviews from that era over two decades ago, Clarence often ran the engines under test on 15% lubricant fuel, and he even did a test of the exact fuel I used to run (and hope to run with AGAIN), the four stroke glow fuel from FHS Supply, at http://www.fhsoils.com/model_prices.html ., which I used to order with their proprietary synthetic oil at a 17% oil level, and 10% nitro content.

Also, in MANY of his four-stroke engine review articles, Clarence mentioned that engine manufacturer's instruction sheets would often specify higher lubricant content percentages of about 19% to 20%, but he felt that if a modeler became really experienced in setting up their four-stroke mills, they should easily be able to use oil percentages of about 15% on a regular basis, to perhaps as low as 12-13% for some engines...not for all of them, though!

When I complete my business degree by this June, and can manage to get back to work again (partially to AFFORD our hobby once more) later this year, I'd be going for a 10% nitro, 15% oil content FHS Red Max four stroke "custom blend" fuel, with no more than about 1% to 2% of the total fuel volume being castor oil in there (as part of the 15% figure), to guard against "lean runs", if I ever got ham-handed with any four stroke mill I happened to be breaking in.

I DO usually "spike-up" the oil content of the first 10-oz (280 ml) tankful of fuel with an extra bit of the FHS synthetic lube to 19% for that roughly first half-hour of running on a brand-new mill, and then run my usual fuel after the first ten-ounce tankful has been run through the new mill to get its break-in going onwards toward completion.

Some brands of four-stroke mills like Saito's fine collection DO require that the mill be kept at a "fast idle" setting (and NO faster) for the first 10 minutes or so of under 4,000 rpm, then after that initial period, opening up the engine for higher revs is all right, always keeping it a bit on the rich side to keep anything from getting "too lean" and potentially damaging the mill.

But for properly broken-in four strokers, perhaps some of us might want to think about Clarence's use of the 15% synthetic oil percentage fuel for our needs...just a bit less oil to slow down the mill, a bit more "combustible content" (methanol & nitro) for better power and somewhat better fuel economy, and just keeping the mill adjusted on the rich side of things to keep any lean runs from occurring.

If anyone wants me to, I'll get a good look and quote one of Clarence's engine tests, to show that he really DID say what I've mentioned him writing about in the RCM-published four stroke engine book he authored - especially about oil content in a glow-ignition four-stroke mill's fuel...

...until then, gotta to head for dinner for the time being...!!!

Yours Sincerely,

The PIPE....!!
Last edited by The PIPE; Feb 17, 2012 at 09:21 AM.
Feb 17, 2012, 01:40 PM
Registered User
Arceenut's Avatar
This article makes good sense to me.

Feb 20, 2012, 10:48 AM
Suspended Account
Originally Posted by djay
I run my engines in up to 50c and 100% humidity with no adverse affects at all.

(from Dubai)

50 C is 122 F nearly close to the record.

You are absolved for a bit of exageration.

No doubt in 50 C and 100% humidity your engine can perform better than you can.

In that weather you will find me in my air cooled home doing some building or household chores .

Feb 20, 2012, 11:51 AM
Suspended Account
Originally Posted by Arceenut

This article makes good sense to me.

I just finished reading the articles that this link brings up.

Yes there is good sense and good knowledge to acquire.

However it does not conclude with recommendations on lubricants and nitromethane content.


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