Why the 25:1 fuel - oil ratio for our engines?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
Dashz

Dashz

Well-Known Member
Messages
179
Location
Spain Andalucia
[Update] Zenoah themselves state in the manuals that their engines allow for a 25:1 to 40:1 ratio .
I have been seeing this for quite a while, from instruction manuals to a lot fellow brappers using this ratio. My question is, why such amount of oil? Generally thats too much compared to weedwackers, lawnmowers or chainsaws which all use 50:1, and these engines are identical to ours.

In my experience I can give 2 examples; I have been running an El Cheapo 100$ 29cc rofun engine with 40:1 for 2 years (about 40-50 tanks ) and the engine works fine, starts 1st pull and hasn’t lost power noticeably.
I have ran the crazy 25:1 for 3 tanks and not only it smokes like crazy (I know smoke is cool) but the amount of carbon build up inside the engine makes me cringe, even after giving hell to the car at Wot for most of the time. (I even fooled a spark plug some time ago)

Any practical reason for the 25:1 ratio?
 
Last edited:
Z.hb71 said:
It's all personal preference. They recommend that ratio becuase it's safe and there's probably no way you'll have an oil related failure. We've been over this a few thousand times
Click to expand...
Lol either my search bar doesn't work or something is wrong but I literally looked for “fuel ratio, gas ratio, mixture” etc, and no results came up. Can you link a thread were this has been discussed ?
 
Around here weedwhackers are a dime a dozen. Whens the last time you really went out of your way to save a weedwhacker? With the oil at 25:1 your engine will last a good bit of time as long as you don't run it lean and care for it
 
these guys pay WAYYYYY to much $$$ for their engines so they are scared ! LMFAO , J/K when I raced Karts we ran 25-30:1 depending on time of year. Summer was 25:1

We would run at the very limit of lean carb settings for MAX power ! but used a EGT to know exactly where we were temp wise.
 
For what its worth. Ope makers have the EPA to deal with. Oil causes lots of emissions. Over seas most ope starts at 33 to 1 and goes up from there. The 25 to 1 is scardy bull. Modern oils are a wonder. I run 40 to 1 in everything. Saws, rc, trimmers, snow blower, blah blah blah. Run whatever you'd like. Anything below 30 to 1 is just a waste of oil imo for 99% of us.
 
Never had an oil related failure to date. Most of us arnt racing, or holding high rpm for long periods of time, ie theres no point. I mean for crying out loud. 30 weight engine oil was mixed at 25 to 1 ratios, and tour telling me a modern oil needs the same ratio? Nah not buying it for a second, not for the average basher at any rate. Rpm, load, and duration dictate oil ratio. Our engines are mostly 20k rpm and down, and for most of us they rarely see that rpm for sustained times. Then theres the load placed in the engine, the hardest load we place on our engines is acceleration, with few exceptions. (Speaking strictly land based rc here) then you have duration, the combination of high rpm, and sustained load. Yep again most of us don't really qualify. If we want to talk strictly about racing, that's a different story. Engines tuned on the bitter edge of too lean benefit from the extra oil, to a point. The oil reduces the octane rating as well. And another point chop your plug and refer to one of the how to read your plug threads, guess what? Your plug will tell you if your running the proper ratio as well as proper jetting.
But hey, I'm an idiot, run what you want, its your engine
 
Rep732 said:
Im just ball busting. And sean what is sustained high rpm to you. I tend to do some long field blasts wide open for over 8 seconds
Click to expand...
I wouldnt classify 8 seconds as a long duration. For shortest hardest duration I would have to give that to a scale dragster, or long straightaway. The hardest loaded rc engines I can think of would be a toss up between boat racing, or flight. (Specifically rc heli during 3d flight) I doubt as a basher it's an issue needed to worry about till you've 30+ seconds at the least. Even then depending on your state of tune, it's a not going to be a major issue. Again imo.
 
I run 50:1 in my leaf blower and that puppy stays at WOT for 20-30mins. The motor is holding up better than the plastic mount and straps. I'm the 3rd owner too!

My cars get 32:1
 
Last edited:
Back
Top
✖
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks