40:1 instead of 50:1?

[clyde]

I don't believe , with a high quality synthetic oil, at 32 to1 , you would have more build up than with the stock oil recommendation.  I think the motor would  last longer also.  I base this from racing 2 stroke motorcycles for 30 yrs.  High quality synthetic oil is superior.  Noticibly.  Especialy two-cycle oil, in high reving situations.  I think the oil is more important than the ratio(not an amsoil 100to1 fan).  A high quality synthetic oil will lubricate well at 50to1, but it will have better power and lubrication at 32to1 with no negetive effects.  All of this is just an opinion not fact.

[bwalker]

Doc, would you care to tell us the differance bewteen Stihl orange bottle oil and a oil from say 1984? Are both not API TC oils both formulated with a mixture of light petroleum base oils, a heavy petrol brite stock and additive package made with a calcium based detergent?
 Advancments have been made in lubrication, but the saw makers havent really picked up on this until the last few years. They have now began to use PIB blended oils to increase cleanliness over the old brite stock based oils.
 

If you ever have a chance to look through Stihl's engine failure diagnostic manual you will find that running a mixture too rich say 33:1 leads to excessive carbon build up and piston scoring on the exhaust port side and ring sticking as the carbon build up falls back in on the piston

Again, there is no build up with the proper oil. All of the jap motor cycle companys spec 32:1 ratios, even with dino oil.

[StihlDoc]

In the USA, the percentage of bright stock was changed and the treat rate and chemistry of the additive also changed in 1989 when the mix ratio recommendation and bottle sizes changed from a 40:1 to 50:1 mix ratio.

[bitternut]

StihlDoc I am getting confused as heck following this thread. I use Stihl oil that comes in the small bottles ( 2.6 oz I think ). I mix it to one gallon of fuel. Could you tell me if I am right in doing so. I run this mix in my Stihl 026 Pro winter and summer.

[sawguy21]

You people south of 49 need to go metric. One 100ml bottle to 5 litres of gas = 50:1. Simple The imperial system drove me nuts. I needed a wall chart with all the different mixes in the old days. 2.6 oz to the U.S. gallon sounds about right.

[beenthere]

StihlDoc I am getting confused as heck following this thread. I use Stihl oil that comes in the small bottles ( 2.6 oz I think ). I mix it to one gallon of fuel. Could you tell me if I am right in doing so. I run this mix in my Stihl 026 Pro winter and summer.

UR doing it right. Says right on the bottle that it is to be mixed with 1 US gallon of fuel (I use premium as it doesn't have ethanol in it).

[Rocky_J]

when all else fails, read the directions on the label... 

[Todd]

Its all so clear now!!???

[bwalker]

In the USA, the percentage of bright stock was changed and the treat rate and chemistry of the additive also changed in 1989 when the mix ratio recommendation and bottle

Which is a the same approach that was used in the early 80's.

[StihlDoc]

Run what your instruction manual states or whatever ratio and brand of oil you are comfortable with and have confidence in. If you elect  to use something different than a manufacturer recommends, don't complain that the product is not up to standards if you happen to experience lubricant or combustion deposit related failures in the future.

The amount of oil to gasoline in the USA to achieve a 50:1 ratio is:

1 gallon gasoline to 2.6 ounces oil
2.5 gallons gasoline to 6.4 ounces oil
5 gallons gasoline to 12.8 ounces oil

Items to note for small air cooled two-stroke engine lubrication:
a) Small changes in mix ratio won't be noticeable to you or the engine (e.g. 40:1 vs. 50:1).
b) Higher mix ratios (e.g. 50:1, 80:1, 100:1) allow the engine to produce more power as long as the oil has the necessary lubrication properties to overcome friction.
c) Don't run outboard motor oil in high performance chain saws and don't use high performance chain saw oil in outboard motors.
d) Synthetic oils are usually better performers than petroleum oils.
e) Manufacturers do extensive testing to come up with an oil formulation and mix ratio that has a reasonable price and works well in their products under most circumstances.

[bitternut]

Thanks, I will continue as I have been at 50:1 with Stihl oil.

[clyde]

stihl-doc
why do you get more power when running less oil in the mix?
I don't believe this to be true.
testing has shown us that a two-stroke motor makes more power with more oil in the mix all the way until the spark plug will foul.

[StihlDoc]

The BTU energy in gasoline creates power. Oil is not as volatile and does not produce the heat energy that gasoline does. But oil does reduce friction and helps piston rings to seal. It is possible that you could feel an increase in engine power by adding more oil if the engine cooling is not efficient, the piston/cylinder tolerance is tight, or piston rings are worn.

[bwalker]

Mac authored a SAE paper int he 70's that conlcuded that a two stroke made more power as the mix ratio was decreased up untill plug fouling became a issue.

"The BTU energy in gasoline creates power. Oil is not as volatile and does not produce the heat energy that gasoline does. "
Wouldnt oil have a higher BTU than gasoline and it sureley produces heat energy when it burns.

[clyde]

Mercury outboard motors came to the same conclusion also.
It really doesn't matter what the btu's of the oil is.  It is really not burning in the cumbustion(not much anyway).  This is why the engine runs leaner with a higher oil ratio (less gas mixed w/same amount of oxygen).  The oil volume isn't even figured in because it is not burning.  Most of the oil is burned off in the muffler.  The increased power (dyno-proven time and again) is more due to better ring sealing (higher compression) than less friction (not a bad thing).


****32-1****

[kkesler]

What would the consensus be on the appropriate mix for my Homelite C-5 with modern oils?

Here is what it says on the saw:
http://www.keslers.net/images/open/c5-mix.jpg

(16:1)