Hello Gang! I run a small fleet of Ford E-series wheelchair vans (90% city, 9.5% highway, 0.5% idle)They are on OEM recomended 5W20 Motorcraft with Motorcraft filters. Schedule says 5k interval heavy duty use, 7.5K "normal" use. I think I should consider my application "heavy-duty" Question - should I stick with OEM recommendation or like in all my other personal cars I use M1 extended with extended filter once a year. I agree once a year for "industrial" application should be a bit of a stretch but maybe twice a year? Thoughts? Thanks!