small engine: use "premium" gas?

[timbirr]

I'm not an expert in this, but I assume Stihl engineers are. I own timberland and have a variety of Stihl and Husky power tools, ranging from the small "home trimmers" to professional brushcutters, chainsaws and pole pruners.

Stihl states quite clearly in their owner manuals that 89 octane or above is to be used, at least with all the equipment I have. You can read the manuals online at

They state specifically that lower octane ratings may cause higher temperatures in the engine and increase risk of piston seizures.

Considering that when I do run my equipment, I often run it for five hours or so, I would rather keep it cooler, so I spend the extra dime a gallon and get premium for my equipment.

So, run the higher octane fuel (89 or above) if you trust Stihl. If not, well...

[Eigenvector]

You are absolutely correct, you should ALWAYS go by the owner's manual - never what a salesman in the store says. As to what we say online, newsgroups are an excellent resource for information that you might otherwise not know, but always start with the owner's manual.

[HeyBub]

But WHY should you always follow the owner's manual (or at least CLAIM you followed the manual)?

a) You may void your warranty if you don't follow the instructions and limitations therein. b) You have an unassailable position when the device - used according to detailed directions - maims you.

[zxcvbob]

Echo recommends 89 octane gasoline, so I usually use mid-grade gas when I mix a can of 2-cycle fuel.

I've found that if I buy a gallon or two of premium in the spring for my

4-cycle small engines (lawnmower and tiller) they start and run much better for that first startup. (they usually have a little bit of stale gas in the tank leftover from the previous year.) By the time I use up that first can of gas, I switch to regular and they run just fine on 87 octane. All grades of gasoline are 10% ethanol here.

Bob

[timbirr]

LOL:

"Dear Augustus Stihl:

I done used your chain saw and put in 89 octane gasoline and the tree I cut fell on my truck, completing destroying the vehicle. Since I followed directions and used the proper grade gasoline, I feel your company owes me a new Ford F-150...."

;>0

[George E. Cawthon]

I presume your string trimmer is 2 cycle. Gas and oil are mixed. What do you think adding oil to gas does to the octane? What do you think a slight miscalculation in mixing the oil and gas will do to octane?

You are right to be surprised. It is amazing how much BS some people spew. "Cleaner, filtered more, and lower octane gumming" are all nonsense that an uneducated person would say.

What you need to read is not on the net but in the manufacturers handbook. Almost all small engines

2cycle or 4 cycle use regular gas. Most automobiles use regular gas.