Small Engines (Lawn Mowers, etc.)/Chainsaw fuel ratio


I just replaced the cylinder, piston, and rings on my efco 181. I would like to know the best ratio to mix the gas to make the engine last the longest. Any information is appreciated. I looked for chainsaw engine failure analysis but could not find much. It would be interesting to see a comparison of the internals of one saw run on 25:1 and another on 50:1. I have done a lot of research but everyone has a different opinion. I have heard old timers say run it rich because it protects better and worst case scenario foul a plug or plug the exhaust. I have also been told industry standard is 50:1 now and any more oil than that burns hotter and could damage the saw. I know how to adjust the carb properly. I have stihl snythetic oil. I also purchased two blue max saws that recommend 25:1. If you have any resources or links with information I would appreciate it. Thank you

Mainly opinions.  True about running more oil regarding the carbon deposits and fouled plugs.  You could run 40:1 and then adjust the carb high speed a little rich, more fuel, but you will loose high speed RPM.

I use 50:1 Stihl for all by equipment but mix it to about 40:1, just use a little over .75 gal of gas.  I have had my Echo trimmer and blower for about 17 years and both still run great.  i use the blower year round so the engine get lots of hours on it.

I've never seen any rings build up with too much carbon due to a richer oil mix but I have cleaned lots of spark arrestors.

How long did the last cylinder and piston last?


Small Engines (Lawn Mowers, etc.)

All Answers

Answers by Expert:

Ask Experts


Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

©2017 All rights reserved.