5W40 instead of 10W40?

Originally Posted by hardhat_harry

Tbh I dont believe their is a difference between bike and car oil anymore.

Not true, Car oils have 'extra slip' additives, Motorcycles cannot use oils that contain these - the wet clutch wouldn't work!
As to what oils contain what additives, the only way of telling is by the API/ACEA ratings.

Just something I learnt from my Castrol talk back in my apprenticeship.

Originally Posted by minitwin49

Not true, Car oils have 'extra slip' additives, Motorcycles cannot use oils that contain these - the wet clutch wouldn't work!
As to what oils contain what additives, the only way of telling is by the API/ACEA ratings.

Just something I learnt from my Castrol talk back in my apprenticeship.

not all car oils, only "energy conserving" car oils that are generally a viscosity of 30 or less warm so car 10W40 or 5w-40 or 0w-40 are ok, but not 10w30, 5w-20, 0w-20, etc

and as far as "won't work" is extreme I know for a FACT they will work as I have used energy conserving in my SV without any harm in a pinch to top off and stayed in till next regular scheduled oil change.

your better of with a full crank case containing some car oil than you are running low on motorcycle specific oil

the statement is better worded, energy conserving car oils "might" make wet clutches slip

Originally Posted by RandyO

and as far as "won't work" is extreme I know for a FACT they will work as I have used energy conserving in my SV without any harm in a pinch to top off and stayed in till next regular scheduled oil change.

the statement is better worded, energy conserving car oils "might" make wet clutches slip

I have used it as a top up for about 300ml and it was fine, but if used as a full drain it does cause this, I have ridden a wet clutch motorcycle that had this oil put in when the customer serviced it, the clutch slipped badly and new plates were required.

Well if it's anything... I have always used just a 10w-40 from Halfords to top mine up! As bad as it sounds I didn't actually know there was a difference. I though 10w-40 was 10w-40 whether that be a car or a bike...

Never experienced a problem though

Now I know... Ops!