I have a 2001 Honda Rancher ATV 4x4 (ES350).
Up to this year I ran 10W-40 synthetic (Amsoil) but this year went to 20W-50 synthetic. All my riding is at temps over 40°F and according to Honda Service Manual (just found one) its OK to use. I would think 20W-50 would be the best choice for hard working engine in hot temps. I would not use anything less. If yours is anything like mine, it seems to run hot when it idles and using a good synthetic oil might be a wise choice if you intend to keep the machine for a long time.
High-temperature operations often lead to the thermal degradation and oxidation of conventional oils, which leads to the formation of deposits, sludge and varnish. Synthetic oil withstands thermal degradation and oxidation at higher temperatures than conventional oils do, ensuring clean, dependable performance in high-stress, high-temperature operations. Especially in air-cooled engines.
I change once a year which is about 250 miles more or less. Last year I hardly rode it any great distances but used it often so that last oil change was in 2002, just forgot about it as I had other things to worry about.
I highly doubt the need to change every 6 months on a rarely used machine if u use a good oil.
btw-Local ATV dealer will install any lubricant you want. The sell them all including Amsoil which they have sold and raced for many years.
[ April 18, 2004, 08:56 AM: Message edited by: Mike ]