So, from yesterday’s post you know the amount in ppm (parts per million) (by weight) of various stuff in the the used oil of my bike. It’s one thing to look at a ppm, but what does it look like?

I wondered that.

If, for instance, I wanted to know how big a ball of aluminum was worn off my engine… what would I find?

I ran some simple math through Mathematica to start with. (Likely overkill, but screw it for now. I’ll run the rest in a spreadsheet I guess.)

In[19]:= DensityOil := .8881 (* kg/l *)
In[53]:= TotalOilWeight := 4*DensityOil * 10^3(* g *)
In[54]:= TotalOilWeight
Out[54]= 3552.4
In[27]:= WeightAl := TotalOilWeight * 7 * 10^-6 (* g Al *)
In[56]:= WeightAl (* g *)
Out[56]= 0.0248668
In[42]:= Alcm3 := WeightAl / (ElementData["Al","Density"] * 10^-3)
In[43]:= Almm :=Alcm3*10^3
In[57]:= Almm
Out[57]= 9.20993
In[62]:= Solve[Almm == 4/3* Pi*(d/2)^3,d,Reals]//First
Out[62]= {d->2.60067}

In the four liters of oil in the bike, if you took out the aluminum you’d get a BB around 2.6mm in diameter.

Where did it come from? The case and cylinders are made of the stuff. Though, the cylinder walls have a hard coating of Nikasil on them.

Honestly I don’t really know where it came from. But it shouldn’t be a bit wear item at this point. I’m guessing it’s still just wearing in of the engine. It’s barely broken in now, and this batch of oil came from the 600-6000 mile chunk of break-in.

The real interesting stuff is going to be from the next change. :-)