Viscosity question

[TxRider]

The manufacturer recommends 20w-40 wt oil for my Yamaha FZ1. Would 5w-40 wt in a synthetic be suitable? I figure that film strength cold, although of short duration is still a consideration and so I should be looking at 15w-40 conventional oil. Anyone with technical expertise in this area, I would appreciate hearing an opinion.

 

[DNS]

5W40 synthetic will work fine as a replavement for the conventional 20W40. The reason 20W40 is reccommended is not because the cold film strength of 20W is needed at atartup but because the 20W40 won't shear down thinner than a straight 20. However, the synthetic is likely to be at least a 5W30 long after the conventional would have sheared to a 20W20. The 5W40 synthetic has more than enough cold film strength and may in fact reduce engine wear because it gets pumped to the moving parts sooner after startup.

 

[msparks]

Speaking of shearing,

I would be more apt to find a 10w40 or a 15w40, which will have less VII's than a 5w40. Unless you are riding in Minnisota in January, the 5w40 is not needed.

Just my opinion though.

 

[Jay]

I agree with msparks. Delvac 1 5w-40 shears significantly in my Honda VFR (but protects very well) even though it's synthetic.

I also agree with you that cold flow is important and that 20w-40 is thick stuff when cold. You can do better. A good shear-resistant synthetic like Amsoil's 10w-40 is a good compromise.

 

[penzdude]

i think another reason 20-40 is recommended for your fz is that yamaha just so happens to offer it in their "yamalube" lubricant line. nah, that wouldn't be it....

 

[XS650]

15w-40 dino HDEO oils do about as good as any xw-40 dino oil in motorcycles.

 

[DNS]

I still maintain that in general, a 5W40 SYNTHETIC will shear down less than a 15W40 dino oil. However, I agree that a synthetic 10W40, 15W40, or 20W50 will probably be more shear stable than a 5W40.

 

[TxRider]

The 15w-40 synthetic looks like the way to go but it looks a short list. Choices look like costly 10w-40 synthetics or cheaper 15w-40 dino. This may be the time to look into Amsoil even though the cost remains an issue. The Shell Advance line also looks interesting because there are more viscosity offerings. Unfortunately they still haven't made it available in the US. Inquired a year ago and got some vague reference to they were looking into it.