Thread: Problems with Stihl Ultra Oil

I'm not sure if anyone else is having this issue or not (and I'm guessing people are/should be). In one month, I have had an 036 Pro, 192T, and just cause a Mantis Tiller 50:1 all bite the big one and have scored bores. I noticed the engines were running rough, and would have to adjust the carb slightly. In the long run, something was causing the engine to run hot, and I was most likely doing is making the engine run leaner. The one thing between all 3 that I have switched is from HP Super to HP Ultra with 93 Octane gas. I know that Stihl only requires 89, however, the dealer told me when I switched that 93 is better in 2-cycles. When I questioned the dealer (and an e-mail to Stihl) they say that Ultra is the best, and should have no change other than cleaner running engines.

One thing that the dealer has said was that ethanol content in gas will be increasing from 10 to 15% by Jan 1, 2012. He recommended using ethanol free gasoline from Shell to mix with the Ultra. However, a warning he also said is that any engine made prior to 2007, with a carburetor will have issues after Jan 1.

Is anyone else in the same boat? I'm rebuilding the 036, and just bought a brand new 362 because parts for the 036 won't be in till the end of September.

It's not the oil. You probably leaned them out too much. How old is your mix?

Three engines in a month is not a coincidence, did you mess with all three carbs? And you need a new dealer, end of september for parts? Maybe he wanted you to buy a new saw....

The new Stihl oil should be ok even if there is significant alcohol in the gas,after all 2-strokes run fine on pure alcohol providing the mix oil is compatable.The Stihl oil should be ok,alcohol(In the gas) just doesn't like to mix with ordinary mineral oil.
I would do a little test for myself with the Stihl oil,I would pour maybe a cup of alcohol into bottle and then add some of the Stihl oil,shake it up and it should mix. Mineral oil just will not mix as you would find. I think the Stihl oil is synthetic,should be ok.
I've not tried the new Stihl oil,but synthetic Amsoil mixed with pure alcohol fine so it would be ok with gasahol...
I would think most modern oils in USA would be compatable with gasahol,since you guys have a lot of it.

Originally Posted by DSS

It's not the oil. You probably leaned them out too much. How old is your mix?

Three engines in a month is not a coincidence, did you mess with all three carbs? And you need a new dealer, end of september for parts? Maybe he wanted you to buy a new saw....

I make fresh mixed gas every month (college professor always said that any mixed gas only lasts about a month before it gums) and generally I use a gallon a month. I did mess with all three carbs, as the engines were still running crappy after i did normal routine maintenance.

Parts are coming from Bailey's FYI.

I have been running Stihl HP Ultra for about 5 years now. Not a single issue. Mix 50:1 and run it in all my 2 cycle stuff.

Before the gas was 10% alcohol, ran high test. About 2 years ago, we could not longer get "good" gas around here.

Went to 100 LL AV fuel and have never looked back.


I have to wonder if there was any possibility of a fuel issue which resulted in all the failures.

Was any of the equipment sitting for a few months at a time with fuel in it?

Originally Posted by PA Plumber

I have been running Stihl HP Ultra for about 5 years now. Not a single issue. Mix 50:1 and run it in all my 2 cycle stuff.

Before the gas was 10% alcohol, ran high test. About 2 years ago, we could not longer get "good" gas around here.

Went to 100 LL AV fuel and have never looked back.


I have to wonder if there was any possibility of a fuel issue which resulted in all the failures.

Was any of the equipment sitting for a few months at a time with fuel in it?

No, the majority of my 2-cycle equipment runs at minimum 1 time a month. The Mantis was first, then the 192, and finally last week the 036. Essentially in order of bad to good quality.

Your professor should stick to art, history or whatever he is teaching; gasoline is good for several months provided it is kept in a relatively stable environment. I run 50:1 in everything and have for about 3yrs. I have had zero oil-related failures. If you are using Ultra, you should be OK with mix that is several months old. I have many saws that sit for months bw use and fire up without any problem. You messed up the settings of your carb, and you dealer is lousy if he can't get parts in less than a month.

Originally Posted by nmurph

Your professor should stick to art, history or whatever he is teaching; gasoline is good for several months provided it is kept in a relatively stable environment. I run 50:1 in everything and have for about 3yrs. I have had zero oil-related failures. If you are using Ultra, you should be OK with mix that is several months old. I have many saws that sit for months bw use and fire up without any problem. You messed up the settings of your carb, and you dealer is lousy if he can't get parts in less than a month.

Fuel will go bad without stabilizer. Ultra does have a stabilizer in it. Sure I messed up the carb settings, because something was causing the engine to run hotter. I was compensating by adjusting the carbs to run leaner, causing overheating and eventual scoring of the bores. It was already too late, when I'm loosing at piece of equipment to the same failure each week. I have never had to adjust carbs or any fuel related issues in the 10 years I've owned the saws. I'm NOT getting parts from my dealer, but from Bailey's Online.

I have kept mix up to 8 months with no problems. Actually some longer, but it gets dumped into the mower.

Been running Stihl Ultra lately, also with no problems.

Did the gas in all 3 machines come from the same batch of mix from the same gas can? It's possible to make a misteak-oops,mistake,and accidentally mix wrong? The last time I saw 3 of a guys saws sieze all around the same time(Very exp. faller) someone made a mistake(No oil)mixing his gas.
Or fiddling with the high speed screws can do it too.

Tell me,are the pistons seized and scored all the way around(Oil problem),or are they only siezed on the exhaust port side(Lean HS screw). That tells half of the mystery right there,if they seized from oil mix or lean seizure...

Originally Posted by WHGStihl

Fuel will go bad without stabilizer. Ultra does have a stabilizer in it. Sure I messed up the carb settings, because something was causing the engine to run hotter. I was compensating by adjusting the carbs to run leaner, causing overheating and eventual scoring of the bores. It was already too late, when I'm loosing at piece of equipment to the same failure each week. I have never had to adjust carbs or any fuel related issues in the 10 years I've owned the saws. I'm NOT getting parts from my dealer, but from Bailey's Online.

there's your problem.

I talked to my boys at the stihl dealer here that I use religiously, and when I asked about the HP Ultra oil compared to the High Performance oil here is what I was told. The HP ULTRA oil was designed to work better with the new 4mix motors, the Ultra oil was made because of the new emission BS. It will work in the all stihl products, HOWEVER, The older Stihl equipment was designed to work with the standard High Performance oil(hence the term High Performance). Therefore you should continue to use the oil that the products you have were designed to use. And they said if you have been running them on the regular HP oil, and aren't having any problems, don't switch. Stick with what works and what they were designed for.

The only thing that we use the Ultra in is two 4mix weedeaters, and FS90, and an FS110. I hate those two compared to my FS85 PRO, I would have the 2cycle over the other two anyday.

Originally Posted by trappermike

Did the gas in all 3 machines come from the same batch of mix from the same gas can? It's possible to make a misteak-oops,mistake,and accidentally mix wrong? The last time I saw 3 of a guys saws sieze all around the same time(Very exp. faller) someone made a mistake(No oil)mixing his gas.
Or fiddling with the high speed screws can do it too.

Tell me,are the pistons seized and scored all the way around(Oil problem),or are they only siezed on the exhaust port side(Lean HS screw). That tells half of the mystery right there,if they seized from oil mix or lean seizure...

It's a scored on the exhaust side, the compression in the 036 was 60 psi, and I know that 120 is considered bad. I know I leaned it with the HS screw. The point is, what caused the engine to run bad in the first place. I use pre-mixed bottles of Ultra made for gallon usage, I always poor the oil in the gas can and then add gas.

I agree seen easy mistake's happen. Could have over mixe'd, been to rich and run rough. Then leane'd out too much to compensate.

There are a lot of loyal Stihl Ultra users on this forum, good luck swaying the crowd. Maybe pics of the damaged pistons/cylinders would help.

What oil are you going to run in the equipment when it is back togehter?

How did you retune the equipment? By ear? With a tach?

My dealer once mentioned that when switching from dino oil to Ultra, or any other high quality synthetic, failures could result from carbon being loosened up on the piston and breaking loose.