Which Octane Gas for Kohler Command - Exmark

[adamrc]

I have a 2010 Exmark Next Lazer Z with a 23 HP Kohler Command engine. I was just curious which octane of gasoline you all recommend using. My dealer said he recommended 89 octane (which is what I've been running since new).

The Kohler manual says - "Octane rating of 87 (R+M)/2 or higher"

 

[exranger06]

I would follow whatever the manual says. There is no need for anything higher than that.

 

[bepperb]

The compression on OPE is generally low enough any gas will work. A lot of times people will recommend higher octane gas because the octane rating lowers while gas sits (which for OPE old gas is used often) and many times premium gas has no ethanol, both of which are good reasons to use it.

Really if you use fresh gas it probably doesn't matter.

 

[Rand]

I'd go with 87 the higher the octane the more likely it has more ethanol in it as ethanol is a great octane booster.

At least around here.

 

[TC]

"My dealer said he recommended 89 octane (which is what I've been running since new)."

Depending on who you're talking to, sometimes dealers have some great insight and experience as to what works well with a given device. Other times, dealer = glorified salesman = having the same level of mechanical inclination as my dog.

On the other hand, you can assume the manual's "87 octane" recommendation had some or much input from the engineeers who originally designed the engine. It's no contest over which source I'd trust more.

 

[lexus114]

I dont use 87 octane fuel in anything I own. Including my out door power equipment. To me, it`s the absolute minimum octane required for a motor to run on. that`s why I use 89 in my ope.

 

[Quest]

Originally Posted By: bepperb
The compression on OPE is generally low enough any gas will work. A lot of times people will recommend higher octane gas because the octane rating lowers while gas sits (which for OPE old gas is used often) and many times premium gas has no ethanol, both of which are good reasons to use it.

Really if you use fresh gas it probably doesn't matter.


I'm with bepperb on this one.

Citing RE: B&S Small engine repair and care (sp?) written in collaboration with Briggs and Stratton, citing that typical flat-head B&S engines run on approx. 7:1 compression ratio, and should be good to take on anything around 77octane or more.

In other words: 87octane (RON+MON divided by 2) should be more than sufficient to run your flat-heads.

OHV may require slightly higher than 87 (then again: system/manufacturer-dependent).

I'd run fresh, clean and doped (with fuel-stabiliser) 87 octane gasoline in my flathead at any given day than, say, run higher octane gasoline (but lost a bit of octane due to decomposition, etc.) citing the gummy deposits and carboning of the combustion chamber.

See my other posting RE: B&S 675 refresh and take a look at the combustion chamber deposits on a 7-season, owner-neglected head and carbon deposits....

Q.