20w50 oil

So we made a huge mistake and took my dads sportsman in to get serviced at the local stealership.( Im the smart one and do my own service on my ex)lol. Anyway it took them literally a month and a half to get my dads quad back to us. Its a 05 sportsman 500 H.O. Then we found out that they put 20w50 weight oil in it. According to the manual we shouldnt run that heavy weight oil. Should we change it out or do you guys think it will be fine? dont want to fry a valve train or anything :) Thanks

Mornin †2005 400ex†
I'd go to Advanced Auto and get some Mobile One 0-40 and put in, It's cheaper then Polaris oil and just as good if not better, I have an 06 500 X-2 and use the Purolator oil filter # PL-14610,, NOT the p-14610

even though that the mobil may be cheaper it is not as good as the polaris oil. its contents are not as good for the engine as the polaris oil. i had hears that it can sometimes even hurt it.

(just saying)