Do yourself a favour and find some unwanted uncool oil that does not have to be anything special and run that in your mix for breakin. Just don't use 100% full synthetic oil.... mix a lil rich for breakin. Now you only get ONE go at this and oem jugs cost plenty so get it RIGHT. NO baby baby easy peasy cutting at half throttle or long idle periods. Brief warm up then straight into some nice big wood and give it hell!! If you want a good break in that could result in say a 2-8% nett power gain over a poor ring seal you need to create as much pressure in that cylinder as possible. Gas pressure is what seats rings. So you need to create it!
1. I have heard from several what I would consider reliable sources (chemical engineer friend, several mechanics) that every brand/type of oil has a slightly different chemical make up. Maybe that is true maybe it's not. Maybe it doesn't mater. But why take the chance. I run Stihl ultra synthetic mix from day 1. And I don't use anything else. I run my cars the same way...same mobil one oil every change. Got 320k miles before I traded it in.
2. I've heard it every which way to sunday to run 40 to 1 to run 50 to 1. I've actually tested both in the 660 on the same day, with the same bar, with new chains, in the same wood, - tune didn't change, the bar temperature didn't change, the jug temp didn't change, the cut times were basically identical as well. Slight advantage on the larger log with the 40 to 1. Bottom line I split the difference and do 92 octane ethanol free with stihl ultra at 45 to 1. That gives me 1.8 gal of fuel to work with vs 1.6 gal (40:1) or 2.0 gal (50:1)
yesterday - I started the saw (took 2 pulls) and I let it idle for about 5-8min to warm up, while I got stuff ready. It was 18 F degrees out. 661 and I were out for 6hrs. First tree was a simple cedar about 12" across. fell it, cut it up. Next was 20" white pine. So guy wanted it in 16s so I got a bunch of full throttle in soft wood quick cuts. I tried to keep the low throttle stuff to a minimum as the saw would be running leaner. After that I cut up a pile of maple. And then cut up a big oak. Finally on tank 4 I was putting some real stress on the saw by noodling the frozen oak. I ended up cutting and stacking a lot of wood. Gas mileage I would say is better than the 660.
See page 36 of 661 stihl manual
"unnecessarily high loads during break in period" - basically to me it says don't really stress the saw for the first 3 tanks.
now I've gone through 5 or 6 660's and I have found the saws to be faster if I did a nice idle period after I first started the saw. maybe im wrong i dunno. I don't have enough money to get scientific about it and buy a bunch of new saws all at once to try it. But doing the break in the way I just described has given me good results.
