Hi it's me again? I lost my owners manual for my 2007 S40 and I can't remember what oil weight they recommend? Is it 10-40W? And which would be best; synthetic or conventional. I'm often confused as to which to use as I only what the best in my bike. Any guidance will be great. Thanks.

Bleemus wrote on 09/05/08 at 14:21:50:


Synthetic, 20w-50 also,  but I'm using Mobil 1 V-twin.   Local Walmart & Auto-Zone carry it, but NOT with the car oils.

There is a 2002 Owners manual to download in the Tech Ref section (look in the index (link at the top).  Only differece between 2002 & 2007 is the badging and the two extra handlebar switched, (Flash to Pass & Hazard Flashers)

My 2008 S-40 manual says 10W-40 or if not available use 20W-50 from 14 degrees up (F). 15W-40 or 15W-50 for temperatures a little over zero (F) up and finally 10W-30 for -4 to 86 degrees F.
There is a caution NOT to use oil that is classified as friction reducing or something to that nature. Do not use additives either as this can affect the clutch. I put Mobil 1 in mine just as a personal preference. (It's only a couple of quarts-my Dodge diesel pickup takes 11 quarts)

Most owner's manual recommendations assume non-synthetic oil, which will break down over time and "thin."  If you're going to use full synthetic oil you can ALWAYS move to the next "thinner" oil.  For example, if the OM says use 10-40, you can use 10-30 or 5-30 full synthetic.  After about 50 hours, most petroleum 10-40s are no thicker than 10-30, and some 20-50's break down to something between 30 and 40...

As a general rule, thinner oil will give you easier starts, better mpg, and cause the engine to run cooler.  Thicker oils generally offer more film strength, shear force & shock load resistance (for gears), less oil leakage, and in petrol only oils, longer life before the oil gets "too thin."

I'm currently using Amsoil 10-40, but am switching to Amsoil 10-30 on my next oil change.  Both are full synthetic & wet clutch compatible.  Just my two cents...but like Jay said, and others have said, there's an oil war here every so often and I guess we were due.