View Full Version : what octane
gas hog
03-19-2001, 03:27 PM
What is the best octane to run in my 125 merc.
Your manual says 87 octane.
Your manual will say a minimum octane of 87. I find my 90 starts easier and idles smoother with the 91.
mbrandt
03-20-2001, 04:30 AM
My manual also says 87 minumum, but it also recommends using the mid range octanes because of the added cleaners in the mid range fuels. I am using 90 or 91.
Mark
I first ran mine with 89 octane and when I troll for longer periods it would cough once in a while. So I changed to 91 and it idles smooth all day, also starts better in colder weather. I also run Sea Foam in it.
As you know the higher the octane the slower the fuel burns. In a two cycle engine snowmobile or boat, gas can cause you alot of problems. Lower octane gas especially oxygenated burns faster and alot hotter and can be harder on your engine. I found that with oxygenated fuel, if I turn my motor off for 1/2 hr or so I have to choke the motor to start it. I think because the motor is running hotter and the fuel evaporates faster because of the alcohol . I then found with Non Oxygenated premeium that the motor did not have that problem. I would run High Octane Non Oxygenated if possible or if not available just high octane fuel
Try this site for a list of known non-oxygenated fuel stations in Minnesota. msra.com/non-ethanol.htm.