I have a 05' 400ex what type of oil should I switch to for winter. S. louisiana so I would say between temperatures of 40 - 70? I run honda hp4 20w-50w now? Just wondering for my next change.

 

And all stock

 

With the air cooled 400EX, you want to run oil that is on the thick side to help protect the cam area. 20W50 is a good choice for hot summers in the southern states. It is cooler in winter, but not so cold that you will ever need one of the full on "winter" oils like 5W30 or 0W30.

40-70 degrees is perfect for 10W40!. 10W40 will go down into the teens and up to 100 degrees, so you will right in there.....

HP4 is good oil. It is a petroleum/synthetic blend, and contains a fair amount of ester in it (based on the smell), and a pretty robust additive package.

I personally like the ester based full synthetics, like RedLine, Maxima Extra, Klotz, or Motul....all of which are however very highly priced.

 

Thanks for the response, I am not really worried about the prices of full synthetics cause I think of oil as cheap insurance. What I am worried about running full synthetics is that I heard that the bike may develop leaks that were not there before. Thanks again for your response!