Pre-Mix ??

[bwalker]

power or more heat & fouled plugs?

You will not foul more plugs with a richer ratio. Your engine will also not run hotter. 50:1 is to satisfy the goons at the EPA and is not the best thing fort your saw.

 

[stihltech]

50 to 1

OK, 50 to 1 is bad fort everything. BUT, why am I now rebuilding LESS saws than I did 10 years ago. More sales per year, more customers. What am I doing wrong? Why are the saws lasting longer in everyday use?

 

[bwalker]

OK, 50 to 1 is bad fort everything. BUT

I dont think its a question of 50:1 being bad, but one of 32:1 being better. Your saws motor will not implode if run at 50:1.

 

[mikey]

Hi fella's,I'm not in disagreement.I remember reading,on this site,by a man who I believe, was a petroleum engineer.Anyway,I believe he stated that more oil burned hotter and that pre mix oil today (synthetic) is superior and there was no need to richen the ratio.It was a while ago, but I'll look for it.Good Day Gentlemen.

 

[bwalker]

Mikey, It was dagger that made the comments about oil burning hotter. While I respect dagger( hes a industry insider and engineer) I also respectfuly disagree with him on this issue. If the extra oil did indeed burn hotter I find it hard to believe that a extra 1.5 ounces per gallon would make a measuarable differance. Also it seems to me that if oil evaporates at a higher temp than gasoline it would in fact leach heat out of the combusation chamber by sucking up heat to vaporise it proir to combustion. With more oil you have better ring seal, more comp, and less wear. Notice that no oem reccomended 50:1 before the epa started becoming a problem. I know some people will say "well oil tech has improved since then". I would reply to that by saying that the mineral based mixes from sthil and husky are not high tech. By looking at the msds files for both it appears that both still use petrol bright stock bases with very little additization(essentialy 70's tech). If they where to have some sort of high CST ester base I could see a 50:1 ratio, but 50:1 on low cost/performance oil it seems a bit odd to me. Stihl Tech mentioned that saws lkast longer now than they did in the 32:1 days. This may be true, but I would bet it is not because of lubrication. Cylinder coating, bearing, piston/ ring tech, and QC/tolerances advances every year. In all probability this is what is responsible for Stihltechs observations. Fire away.LOL

 

[WRW]

Partner was recommending 50:1 back in the 70's (with Partner mix). I don't think EPA was a consideration at that time.

 

[mikey]

Well, if 32/1 is better than 50/1 then is 20/1 or 16/1 even better?Or what about 40/1?I'm sure the type and quality of oil makes a difference.Are the oil manufactures influenced by the EPA?

 

[jokers]

Hey Ben, maybe the failures in the "old days" of 32:1 were due to carbon flaking off and scoring the cylinder wall? Just guessing cause I didn`t have any failures then either. I think keeping the fuel/air ratio right is just as important as keeping the oil ratio spot on. I don`t doubt that on a comparative basis, OEM mix oil is still in the 70`s but it sure does seem to burn cleaner. BTW, I was there, in the 70`s, and it sure was smoky. Russ

 

[StIhL MaGnUm]

It sounds to me like there are'nt to many of you who like the 32:1 idea,I just alway thought the more oil the more or better the protection from piston seizure.I guess 40:1 would be better than 50:1 anyways,but I'll wait to see what everyone else is doing with their oil...

Later Rob...

 

[tundraotto]

a good ratio is definately 32:1. i think the expertise of the saw gurus here on the site have lots of PRACTICAL experience on this.

now hypothetically more oil is better, but i also think the higher the oil ratio the lower the mixed octane will be --> hotter temps. i think the ratio of choice of 32:1 provides us with the extra lubrication we need (that the EPA does not think we deserve) and still allows us to keep the temperatures within spec for the modern (read SYNTHETIC) oils to lubricate. Secondly, due to this lowering of the octane it is important to use as high an octane of good new gasoline as possible to keep the heat (and pingin/knocking FISH!!!) to a minimum. what do you think fellas?

 

[jokers]

I thinking pinging and knocking Fish is a good idea, besides, he seems to like it. Russ

 

[StIhL MaGnUm]

Sounds good to me Otto..

 

[bwalker]

Well, if 32/1 is better than 50/1 then is 20/1 or 16/1 even better?Or what about 40/1?I'm sure the type and quality of oil makes a difference.Are the oil

The amount of oil in your mix should be based on the load you intend to inflict upon the saw. 32:1 is a good mix ratio. 40:1 is a little on the lite side for a highly stressed aircooled high rev small bore motor. CArt racers use 16:1 ratios in Yamaha 100cc aircooled carts so thats not a unreasonablr ratio, although the see much higher dynamic loadings than a saw does unless your trying to cut iorn wood with a severly dull saftey chain..

Hey Ben, maybe the failures in the "old days" of 32:1 were due to carbon flaking off and scoring the cylinder wall? Just guessing cause I didn`t have any failures then either. I think keeping the fuel/air ratio right is just as important as keeping the oil ratio spot on

I agree with you joker. Keeping the filter clean the carb adjusted and useing one ratio is a smart thing to do. Crab adjustments have agreat influeance on engine deposits so you are spot on there. BTW Some of the oils today are so clean with correct carburation that the only residue left in the combustion chamber is caused by the fuel itself. i have a sled like this. It has 3,500 miles on it and the piston is the color of cremed coffe while the head has a small spot of residue on it that can easily be wiped off.

now hypothetically more oil is better, but i also think the higher the oil ratio the lower the mixed octane will be --> hotter temps

More oil mix may or may not decrease the octane of the mix, but this will not increase temps unless detonation or pre ignition is present. This is really a moot point in a stock saw anyhow as the compression ratio is so low. Remeber Otto octane does not "burn"cooler unless abnormal combustion is present. regular and premium pump fuels have very close to the same btus which is the ultimate influeance on burn temp.

 

[bwalker]

[oops double post