"Disclaimer :  I am not a mechanic by any stretch of the imagination"                                                                                                                                                             Hi all!   I recently bought a 2007 GS500 and while the oil looked good upon purchase, i decided to go ahead and change the oil.   I am not sure what type the previous owner put in it,  but i went back with Mobile 1 10-40 synthetic motoorcycle oil.  Oddly,  after filling up the crank case and starting the motor,  i noticed that it idles 100-200 rpms lower. It was 1200-1400 and now it's generally 1100-1300.  Appears to be this case after a few cool downs/start ups.   Is this normal when switching from a mineral based oil to a synthetic?  If he had a heavier oil in it and i went with 10-40,  could that have done it?  Is this even an issue i should be concerned with?  Thanks for any of your input!  New member and i really dig the information and support from this site!

Weather the same? I'm in the East coast and it has gotten hot & muggy. Notice the same symptoms. Normal less dense air.

Make sure you haven't overfilled the cases. Measure the oil level with the bike level ( fore/aft AND side to side). Too much oil will drag as the cranks hiy it and lower the idle RPM.

Ummm. . I'm entirely prepared to be wrong.   But isn't Mobil 1 seething with friction modifiers? .. it's not JASO rated either?! ...

Friction modified oil is a BAD IDEA in a wet clutch situation. . Nearly all bikes use a wet clutch!

Quote from: Janx101 on August 12, 2016, 01:55:48 PM
Ummm. . I'm entirely prepared to be wrong.   But isn't Mobil 1 seething with friction modifiers? .. it's not JASO rated either?! ...

Friction modified oil is a BAD IDEA in a wet clutch situation. . Nearly all bikes use a wet clutch!

The only thing wrong with Mobile 1 10-40 synthetic motorcycle oil is that it's kinda pricey for a GS500.  Never saw a 10w-40 oil that wasn't suitable for a GS, the energy conserving oils are lower viscosity ones like 10w-30, 5w-20, etc that are marked with this donut symbol, don't use with wet clutch:



I like the 15W-40 heavy duty oils like Shell Rotella T, Mobil Delvac, etc for the GS.

Sometimes Delvac is cheaper than Rotella so that's tempting.

I use valvoline 15w40 diesel oil anyway. . Which is jaso rated