and borticus, i ran a dealership (not a mom and pop shop or a discount store), and as you probably know there arent many mowers sold in the winter. I would take my guys (sales ppl and techs alike) to numerous schools during the winter. I know things that are passed along to dealers and not the public for reasons. I know that a modern echo 2cycle engine is designed to run for 5 hrs on straight gas without failing. but if someone on here asked what to do if he ran out of mixed gas and needed to finsh his trimming, i would under no circumstances recommend that it would be okay to run straight gas, that would be entirely wrong and foolish. and briggs makes 2 lenths of filters used on their engines, the reason is tolerence, there may not be enough room to fit the longer one on an engine depending on whats its mounted. i believe in cross reference, but i would never recommend they just screw a fl400s on there as it isnt a direct cross to any small engine filter to my knowledge. several filters will screw on your car, but only a select few were designed for its engine. im a cost cutter too in ways, i buy only sae30 valvoline and only when i can buy it for $1.99/quart, and i already stated what i pay for filter. and if your using m1 and paying full price for it, your paying more for 2 quarts of that, than i am for 2quarts valvoline and the filter. i do buy in bulk when its on sale. i dont buy val sae30 this time and quaker state 530 cause it was on sale. and at those numerous hours ive spent in training, i would like to pass this along straight out of a briggs engineers mouth "multi grade oil used in a lawnmower under load will cause the engine to lose power". so with all this said, i change my oil and filter 3x per year with a total cost of about $21 per year. and i put right at 250 hrs per year on it. its a johndeere gt275 with a 17hp single cylinder kaw its a 1994. it has over 4k hours on it, it has NEVER used of leaked or lost in any way a drop of oil, the motor has never been torn down for any reason, and the dipstick looks brand new, all because i choose to pay a measely $21/yr on oil changes. i grease it, sharpen blades, clean pre filter 2x/yr, and run fuel stabilizer on my last cutting. that is all the maintence that mower recieves yearly.