The reason Exmark wants syn changed at the same rate as dino is because MOST mowing companies do not have employees who CARE about their equipment, let alone sharp blades, oil levels, maintenance schedules, and clean air filters. I was in the green industry for years, trust me, dealers dont like warranty work because it doesnt pay the full shop rate. WHEW!!! Trust me, they will weasel around on warranty work if they can find any fault to put back on you. If it is under warranty then use what they say too unless you want to dump the syn and put in say some dino oil with 20 or so hours on it so it will have a nice 'patina' to it so you can prove that yes you changed oil on a regular basis should you have to take in the mower for service or warranty work.
Your engine is liquid cooled so it wont get too hot anyway and it revs at lower rpm's when compared to a gasser.
Now they push their 5/30 syn as it offers the best protection under all conditions. Briggs once told me nothing but 30 wt dino oil in their engines as that is what they were designed for which is bull. Dealers and manufacturers have been behind the curve when it comes to syn oil. The Daihatsu engine will appreciate a clean air filter more so than syn oil.
