i have a 2006 roadstar will 10w40 mobil synthetic car oil hurt anything?
motorcycle oil in tn. is $9.00 a quart.

check that there are no friction modifiers in it!

car oil can contain such modifiers which ain´t a problem in cars as they generally have a dry clutch, but on a bike with a wet clutch it can cause slippage.

i run bel-ray 10-40 synthetic in mine with no problems

On an oil container you will find a circle. On the upper part it will give the API (American Petroleum Industry) Service designation such as SL/CF with the first S? applying to gasoline engines and C? to diesil engines. For gasoline engines the S? ranges from SA to SL. The R* needs an SE or better (SE, SD, SF to SL) but don't go looking for it

The middle part of the circle will have the grade of oil (15W-50).

The bottom may have the words "Energy Conserving". Don't buy any oil that has this in the bottom circle to use for the R*.

Most auto synthetics have friction modifiers in them. Mobil has various weight synthetic oil which can be identified by the colour of the cap; the Red Cap is 15W-50, Blue Cap is 5W-30, etc.

The Red Cap has now been replace with Gold Cap. I have been using Red Cap for a number of years.

I believe the Mobile 10W-40 has friction modifiers in it. I would not use it.

Doc

thanks doc i'll use 15w50!!!!

Doc you can add api service SM as castrol GTX 10w-40 I am using is SM
Also is there any truth to.... unless you are running hot avoid oils with too hi viscosity range like 50 as they do not lubricate as well at lower engine temps

You are correct, the API goes to SM.

Low number = thin oil = for low temp
High number = thick oil = for high temp

However, it's best to keep the range between the first number (10W) and last number (40) small. In other words, a 5W-50 is less desirable than a 10W-50 for hot temps.

The lower the viscosity the better for low temps (like Edmonton ) but poorer when the temp is high. I ride between 0 and 30 C (32 and 85 F) and find the 15W50 good all round. It's a little 'thick' when the temp is around freezing and the bike is noticeably harder to start if it's been outside all day. So I'd recommend a different weight (5W-?) if you find yourself riding mostly around these temps.

I tried the Valvoline 5W-50 for a while but found the engine too noisy in the summer.

Doc