????? 50:1 is leaner than 40:1 (i.e., the ratio is 50/40 parts of gas to 1 part of oil)
Oil advice from Stihl ...
- Thread starter lilspenny
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Fuel ratio is leaner with 40:1 that is a correct statement
You have to define what lean-ness you mean:
50:1 is leaner in terms of oil
40:1 is leaner in terms of fuel
50:1 is leaner in terms of oil
40:1 is leaner in terms of fuel
You should try torco gp7
Correct...For conventional OPE vernacular for 2-cycle engines, a "leaner" fuel mixture means less/insufficient oil for lubrication purposes. For 4-cycle ICE applications, a lean fuel mixture means too much air in relation to the gasoline constituent (e.g., stoichiometric air/fuel ratio (AFR) is ~14.7 : 1).
I run the VP stuff in all my Stihl equipment. I only get the Stihl oil because it doubles the warranty on a new piece but it just sits on the shelf.
What do you mean by this?
Also, 2-stroke production is limited now only to OPE and some motorcycle models for Africa. Asia, and maybe South America.
How much too lean?
If I tell you - not much at all?
Here is the easiest example in metric system as most precise:
50:1 is 20 ml (or cc) per a liter of gasoline
40:1 is 25 ml (or cc) per a liter of gasoline
Now, get some measuring cup or a spoon and see for yourself how much 5 ml difference is. For reference a teaspoon is 4.8 ml and a table spoon is 14 ml.
So you are telling me that an extra teaspoon of oil in a liter of gasoline (for liter imagine a bottle of oil which is a quart - a little less than a litter) makes the fuel leaner because it has more oil and less gasoline?
I can tell you it's almost the same AFR, but your engine is better lubricated, especially at high RPM.
I’m still working through my several year old husqvarna low smoke synthetic that Lowes clearanced out. I’m less concerned about brand than I am about the fuel itself. Stihl, echo, husqvarna, it doesn’t matter. It’s a leaf blower, not a Ferrari. My oldest 2 cycles equipment is 25 yrs old and not a single oil related issue.
Japanese.... A late response ... It's really not that simple. Some oils just don't run well in a br800, no matter the ratio, no matter the gas. Some oils make a carbon mess. Many people say they have had good results with certain oils. But... Have their results been in a br800? Have they compared as many as ten oils to see which ran best? Ran coolest? Ran cleanest? Most likely not. I have tried, for example Motul 800 off-road.... It ran dirty, plus it did not run with spunk. It's overkill for my br800. So, finding the best overall oil(s) is a real challenge... It's anything but a "just pick one" and all will be good. Now, my fs131r isn't picky. Nor are many other machines. Stihl Ultra, surprisingly, is one of the coolest burning oils. It also makes a carbon mess. So, is "ashless" important? Perhaps. The ash buildup on 4-mix valves might be an issue. That takes time to assess. So, Stihl Ultra is ashless. But it runs dirty. There is a long list of negatives surrounding most oils that might go unnoticed unless compared with other oils, unless piston crowns are viewed, unless temperature is measured, and unless rpm is tuned to max and acceleration from idle is tuned. Which oil runs best? Cools best? Runs cleanest? In a br800?? The br800 is not a 2 stroke. It is a 4 stroke that runs on mixed gas. It runs great. Valves take 10 minutes to adjust and might need to be adjusted yearly, or every 15 years. No set schedule. Not for everyone, but neither are screwdrivers.
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I have a BR 600 and 800. I run STIHL ULTRA @ 50:1 in both of them. You'll have to kill me to get me to stop using STIHL ULTRA.
I don't know why I'm cited, but thanks. Just want to mention that I love 2-stroke machines but currently don't have any OPE. I have experience mostly with 2-stroke street bikes (not racing).
Interesting observations between two 4-MIX® engines and also different 2-stroke oils. Thanks a lot!
What do you mean by that?
Motul 800 is definitely overkill for either for those machines since neither of them runs over 10K RPM like chainsaws and especially like race dirt bikes and go-karts. I have a friend and he runs his race go-karts (that run b/w 15K and 18K RPM) on Motul 710. This oil probably will be overkill for any 2 or 4-stroke OPE running below 10K RPM.
What I can tell you from briefly looking at the two Stihl engines' specs (BR800 and FS131R) is that the first one is more than double the displacement of the second one, but also runs at least 2,000 RPM lower at WOT than second one.
Stihl BR800, 80 cc
7,600 RPM optimum power (per Google)
The PDF below - Oil mixing (p. 10), Engine specs (p. 19), Spark plug: NGK CMR 6H
https://ssc.stihl.com/tsa/techdoc-documents/DVS_STIHL%2FZBA%2FZBA%2F0458-490-8321-B_ZBA_04_01.pdf
Stihl FS131R, 36 cc
8,500 RPM (optimum power); 9,500 RPM (cut off)
The PDF below - Oil mixing (p. 22-23), Engine specs (p. 38), Spark plug: NGK CMR 6H
https://ssc.stihl.com/tsa/techdoc-documents/DVS_STIHL%2FZBA%2FZBA%2F0458-432-8321-B_ZBA_08_01.pdf
I bet the BR800 engine runs much cooler not only because it runs on lower RPM, but also because it's larger displacement - runs more fuel (more oil too) and dissipates heat much better because the larger area of both cylinder and cylinder head. It's just a larger engine.
That's why you have issues with more carbon deposits in the BR800 engine.
You will have carbon deposits regardless if the oil has ash or is ashless because the carbon also comes from the gasoline, not the ash (I'll leave the ash a side for a moment). But running high viscosity, thick oils (like Motul 710 and 800, and Amsoil Saber) at lower temperatures will definitely make more carbon deposits and mess. Those oils may give much better results in chainsaws that run at 12K-13K RPM and hogher. Ash is mostly needed in engines that run higher than 10K RPM but not always.
If you want to use thicker higher viscosity oils like those above just run them at 65:1, but only 800 or Saber and only in the BR800. 710 I would run 50:1 in both engines.
At what gasoline / oil ratio do you run in each machine?
It looks like both engines run the same spark plug - NGK CMR 6H. Number 6 in NGK plugs is relatively hot plug, meaning it's run on cooler engines. The NGK plugs for high temp. performance engines start at 7 and higher. So both those engine don't run really hot.
Also, keep in mind that cleanliness and optimal engine protection are two different things. You have to decide if you want your engines cleaner or better protected.
If I had those two machinery I would run the BR800 on ashless middle ground viscosity oils (9-10 cSt at 100°C) and no higher ratio than 50/40:1. I would stay away form thick high performance dirt bike / go-karts 2-stroke oils.
Middles ground oil (not as thick as Motul 710, 800, Amsoil Saber, but thicker than TC-W3 / snowmobile oils) is for example Motul Scooter Expert or 510 - I think it's the same oil for different markets. It's a 2-stoke synthetic blend JASO FD oil. I run it in my 2-stroke street bikes and they don't run over 6K-7K RPM. 50/40:1 for scooters and 30:1 for street/dirt bikes. You'll be more than fine at 50:1 in the BR800 and 50/40:1 in the FS131R.
Motul 510 2T - eBay
Oil PDS
https://azupim01.motul.com/media/motulData/DO/base/510_2t_en_fr_motul_15000_20251008.pdf
Motul Scooter Expert 2T - eBay
Oil PDS
https://azupim01.motul.com/media/motulData/DO/base/scooter_expert_2t_en_fr_motul_57800_20251008.pdf
If the oil is very low viscosity (5-6 cSt at 100°C) like TC-W3 boat or snowmobile oils I'll go to 25:1 ratio. People also run ATF in OPE at 30/25:1 with good results and that oil runs clean. You can give it a try in the BR800 with any of those oils. I haven't experiment with either one, but those oils may run cleaner.
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Interesting, some people hate that oil, but others love it.
To add up to my long post above. I think I mislead myself in the beginning and probably many people in this thread. In that regard I contradicted myself - first saying don't run TC-W3 and NMMA oils (page 2) and now saying you need lower viscosity oils like TC-W3 and NMMA. That is because I was not familiar with the specifics of the 4-MIX® engines and also nowhere in your thread title or initial post you mentioned 4-MIX® engine.
We are talking about 2-stroke oils and mixtures but in 4-stroke engine. In this case BR800 because you said your FS131R runs fine on any oil. The FS131R runs fine on any oil because it runs at higher temp. which allows the oil to burn completely and cleanly. It runs hotter because is much smaller displacement (run less fuel - hence oil, dissipates heat slower than BR800) and runs at about 1,000-1,500 RPM higher RPM than the BR800.
Also, 80 cc is quite a large displacement for OPE engine. In 2-stroke engines only professional loggers use chainsaws with displacement over 50-60 cc.
4-stroke has twice as less power strokes as 2-stroke engine. Meaning: if your BR800 runs at 7,600 RPM (per Google, they are not mentioned in the manual) and FS131R tops at 9,500 those translate respectively to 3,800 and 4,750 RPM in a 2-stroke engine. Those are relatively low RPM for 2-stroke engines which means it doesn't run hot enough compared to 2-stroke engines. But at the same time you use the same gas/oil ratio as 2-stroke engine 50:1, for obvious reasons - they are the same (even more) moving parts in the 4-stroke engine.
So, what happens is the engine cannot reach optimum temperature to burn cleanly the 2-stroke oil. At the same time you were trying thicker oils like Motul 800 and Amsoil Saber (with higher flash point) because you watch videos that people have good results with those oils but in pure 2-stroke engines (most likely high RPM chainsaws), not in 4-MIX® engines that run at half the RPM.
So, you also need oil with lower flash point for the BR800 and those usually are TC-W3 and NMMA (Pennzoil, Valvoline, Amsoil etc.) oils, but again I would increase initially the ratio to 30:1 or 25:1 (until I find the sweet spot) because they are lower viscosity as well.
Did you try yet the VP Racing at 50:1 in the BR800? It's full synth. relatively lower viscosity oil (compared to regular 2-stroke OPE oils) with lower flash point as well.
Also, I think there are two underrated but great OPE 2-stroke oils:
Stihl HP (orange bottle)
Castrol Go! 2T (mostly available in Canada, if not discontinued all)
However, I think those are not ashless and also are JASO FB oils. They probably would also be overkill for your 4-MIX® engines but are great for high revving (12K and over) 2-stroke chainsaws and vintage air cooled bikes.
Usually in the Stihl manuals for 2-stroke chainsaws says something like:
"Run only Stihl HP or HP Ultra oils at 50:1 ratio. Any other oil run at 25:1."
But that is not mentioned in the manuals of the 4-MIX® engines above. It says only:
"If you mix the fuel yourself, use only STIHL two stroke engine oil or another high-performance engine oil classified as JASO FB, JASO FC,JASO FD, ISO-L-EGB, ISO-L-EGC or ISO-LEGD." - and no 25:1 ration is mentioned.
I think I just found out why - because it's a 4-stroke engine (running at lower RPM and lower temp.), not a 2-stroke as their chainsaws.
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Stihl's key words in their correspondence to me are "fully synthetic" and "equivalent". Thing is, there is no equivalent oil to Stihl Ultra. Ashless, high flashpoint, fully synthetic, with a not so high viscosity. Yes, VP was run and it ran well. Tried 50:1 and 40:1. Both ratios ran sorta hot. 40:1 started producing carbon so I never went to 32:1.To add up to my long post above. I think I mislead myself in the beginning and probably many people in this thread. In that regard I contradicted myself - first saying don't run TC-W3 and NMMA oils (page 2) and now saying you need lower viscosity oils like TC-W3 and NMMA. That is because I was not familiar with the specifics of the 4-MIX® engines and also nowhere in your thread title or initial post you mentioned 4-MIX® engine.
We are talking about 2-stroke oils and mixtures but in 4-stroke engine. In this case BR800 because you said your FS131R runs fine on any oil. The FS131R runs fine on any oil because it runs at higher temp. which allows the oil to burn completely and cleanly. It runs hotter because is much smaller displacement (run less fuel - hence oil, dissipates heat slower than BR800) and runs at about 1,000-1,500 RPM higher RPM than the BR800.
Also, 80 cc is quite a large displacement for OPE engine. In 2-stroke engines only professional loggers use chainsaws with displacement over 50-60 cc.
4-stroke has twice as less power strokes as 2-stroke engine. Meaning: if your BR800 runs at 7,600 RPM (per Google, they are not mentioned in the manual) and FS131R tops at 9,500 those translate respectively to 3,800 and 4,750 RPM in a 2-stroke engine. Those are relatively low RPM for 2-stroke engines which means it doesn't run hot enough compared to 2-stroke engines. But at the same time you use the same gas/oil ratio as 2-stroke engine 50:1, for obvious reasons - they are the same (even more) moving parts in the 4-stroke engine.
So, what happens is the engine cannot reach optimum temperature to burn cleanly the 2-stroke oil. At the same time you were trying thicker oils like Motul 800 and Amsoil Saber (with higher flash point) because you watch videos that people have good results with those oils but in pure 2-stroke engines (most likely high RPM chainsaws), not in 4-MIX® engines that run at half the RPM.
So, you also need oil with lower flash point for the BR800 and those usually are TC-W3 and NMMA (Pennzoil, Valvoline, Amsoil etc.) oils, but again I would increase initially the ratio to 30:1 or 25:1 (until I find the sweet spot) because they are lower viscosity as well.
Did you try yet the VP Racing at 50:1 in the BR800? It's full synth. relatively lower viscosity oil (compared to regular 2-stroke OPE oils) with lower flash point as well.
Also, I think there are two underrated but great OPE 2-stroke oils:
Stihl HP (orange bottle)
Castrol Go! 2T (mostly available in Canada, if not discontinued all)
However, I think those are not ashless and also are JASO FB oils. They probably would also be overkill for your 4-MIX® engines but are great for high revving (12K and over) 2-stroke chainsaws and vintage air cooled bikes.
Usually in the Stihl manuals for 2-stroke chainsaws says something like:
"Run only Stihl HP or HP Ultra oils at 50:1 ratio. Any other oil run at 25:1."
But that is not mentioned in the manuals of the 4-MIX® engines above. It says only:
"If you mix the fuel yourself, use only STIHL two stroke engine oil or another high-performance engine oil classified as JASO FB, JASO FC,JASO FD, ISO-L-EGB, ISO-L-EGC or ISO-LEGD." - and no 25:1 ration is mentioned.
I think I just found out why - because it's a 4-stroke engine (running at lower RPM and lower temp.), not a 2-stroke as their chainsaws.
So, both Motul 710 and VP Racing don't run clean at 50:1 in the BR800?
Can you describe your oil mixing procedure?
There is no "full synthetic" requirement in the Stihl BR800 manual:
"7.2.2 Engine oil
If you mix the fuel yourself, use only STIHL two-stroke engine oil or another high-performance engine oil classified as JASO FB, JASO FC, JASO FD, ISO-L-EGB, ISO-L-EGC or ISO-L-EGD.
STIHL specifies STIHL HP Ultra two-stroke engine oil or an equivalent high-performance engine oil in order to maintain emission limits over the machine’s service life."
Page 10:
https://ssc.stihl.com/tsa/techdoc-documents/DVS_STIHL%2FZBA%2FZBA%2F0458-490-8321-B_ZBA_04_01.pdf
I think JASO FB oils are never full synth and they are not low ash either. But you never used any of them anyway. However, Stihl HP and HP Ultra are JASO FB oils, as far as I know.
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True about the manual. I emailed Stihl and their response was equivalent full synthetic. See my other posts. That would not allow Red Armor as Red Armor is a synthetic blend. Wow, really? But Red Armor is a really good oil. Stihl HP has no Jaso rating. I have run HP Ultra... It ran slightly cooler than any of the dozen or so oils that I tested. Well, Saber was equal. Motul 710 was tested. 710 really offers nothing over Saber or Motorex Crosspower 2T in my br800. It runs hotter, more carbon, plus does not have great spunk. Not a bad oil, just not the best. Mixing procedures? Really? I was a landscaping business owner for 18 years. I've probably mixed more 2 cycle gas than 95% of the people on this forum. I sold my business and am retired. Playing with 2 cycle oil is now a hobby. I have owned and run Echo, Stihl, and Husky. Various models. Used ethanol, non-ethanol, boat oils, gas station oils, dealership oils, internet oils, ... And it amuses me that my mixing procedures are subject to inquiry. I'm not interested in what oils run best in 2 cycle machines. Only what runs best in a br800x. There are jillions of oils that will never grace my presence. Various gasoline mixes, engines, outdoor temps, oils, ... There is absolutely no way to give a practical and scientific test that is financially feasible. If there were, there would already be one. Instead, the only ones are biased and performed by oil or equipment manufacturers. So, my testing is for me and for anyone else who cares what I say. Most people have a favorite oil. Okay. I am narrowing my favorites and sharing bits here and there. In my br800 I really like Motorex Crosspower 2t 40:1. Smells great, too
