Thread: which 50-60cc Stihl chainsaw

3% fuel oil mix for over 60cc saws to keep the clutch side crank bearing cool

2% for anything smaller


3% is 33 to 1 which you can actually use for everything


The critical load area of saws is not the piston, it’s the crank bearings

The highest thermal load is on the piston/barrel clearance

If you keep inside the cases of your saw exceptionally clean then thermal load concern of parts is all but eliminated

Originally Posted by 7mmsaum

3% fuel oil mix for over 60cc saws to keep the clutch side crank bearing cool

2% for anything smaller


3% is 33 to 1 which you can actually use for everything


The critical load area of saws is not the piston, it’s the crank bearings

The highest thermal load is on the piston/barrel clearance

If you keep inside the cases of your saw exceptionally clean then thermal load concern of parts is all but eliminated

Yep, hottest part of the saw is the front right area of the cylinder - right next to the area where the oiler lives so if you have a thermal problem often one of the signs is poor bar oiling - thermal thinning of the bar oil due to crankcase heat. Had one 026 that was really bad for this, slight ding on the front half of the muffler was redirecting the exhaust gas over the front right of the crank case. Weld a little deflector plate on and hey presto no more issue...

As far as oil ratio in the fuel, I've gone to good synthetic or semi-synthetic oil (quality stuff not something from a bulk retailer) and 40:1 for everything. One of these oil brands guarantees their oil against all and any damage at 100:1 in modern small engines - bugger that but at 40:1 I know it's a good mix and if the saw is clean and the chain is sharp there won't be any issue with heat damage. It's one of the things I don't like about TC tipped chains, they cut slower and are draggier in the wood meaning more load and heat on the saw. They have their place, I was using one stumping out a conifer tree stump that just refused to die. See how it likes life in the fireplace... Very hard on gear, bars and clutches and rim sprockets but at least the chain doesn't go blunt in the first second hitting dirt. Saw runs noticeably hotter on the TC chain though, I just don't like them for normal work.