Oil/Gas Mix

For example - Stihl states: 1:25 ratio when using SAE engine oil, and 1:40 to 1:50 when using Stihl two-cycle engine oil.

Generally speaking, I doubt you're going to find a verified example of anyone having an engine problem because they used a TCW (water-cooled rated) oil in a chain saw, or a heavier ratio mix of any oil.

The simple fact is - getting the API two-stroke TC rating is expensive and most oil companies don't bother. That's doesn't mean they don't meet the specs - they are just not spending the money to prove it. To the converse, the TCW rating is needed for many warranties in the boat industry - so for that market - the extra money is spent for certification.

I started working as a saw mechanic back in the 60s. I think I've seen just about every type of failure there is - within that market. I've also cut a lot of wood over the years and use many types of two-stroke-cycle saws and other type of equipment. Many older - especially consumer-level saws used to have very poor cylinder walls. Some just aluminum, some with a thin and poorly bonded chrome plating, and a few with real iron liners. Stihl got famous with their Mahle process. What ever exactly is was - or is - it worked. A saw with a good cylinder wall and real ball-bearing mains (no sleeves or needles) can last virtually forever if cared for. These attributes were common in the 50s, then pretty much disappear later in consumer saws, and now - they're back again to some degree.

Most saws I've seen destroyed - got that way from lugging them with dull chains - or running too lean due to various reasons. Lean with a 16 - 1 one mix is one thing, and lean with a 50 - 1 mix is another. Besides the overheating issue from a lean air-fuel ratio in itself - you also get the additional lack-of-lube problem from it.

I've never burnt up a cylinder wall or piston - ever - in any two-stroke-cycle engine and I use cheap oil and a heavy mix. I'm still running a few old Remington Mall saws, some 50s Homelites, a Hoe, many Stihls from the 1960s, and well as some newer stuff. I've had zero prolems with cylinder walls, crank bearings, port plugging, etc. Subsequently - I don't think the expensive oils amount to any measurable gain - unless you insist on running lean and/or abuse your equipment.

I've got many two-stroke-cycle engines on portable water-pumps that I use in maple sugaring. And, many chain saws from the 1950s to present. Years back - many cheaper saws needed 16 to 1 because of a poor cylinder wall design and main-bearing design. The better saws - like Stilh, Sachs-Dolmar, Husky, Jonsered, etc. had much more durable wall-liners and could stand 40-1 or 50-1 with the better TCW rated oils. Now - with all the EPA regs - even the cheap saws have to put in more durable liners in to be able to run on 50-1. The older cheap saws would burn up pretty fast. That being said, any saw will last longer with more oil in the mix.

The oil has changed too -considering in the 1960s - SAE 30 W motor oil was recommened. The later outboard-certified TCW oil has better protection.

thanks sonny

to find out how much oil you need take 128 divide by the mixture ratio number, that will tell you how much oil to put in a gallon of gas. ie
128 divided by 40 is 3.2

High oil/fuel (16:1) requirements can be driven by the engine having plain bearings. Low oil/fuel (40~50:1) would suggest to me that there are likely ball and/or needle bearings.