E6B only tells you what you already know. You already have instruments that tell you everything on there, and it computes the rest (using fuel to tell how much longer you have to run engine at X settings, and times speed at Y mph, gives you Z duration, etc).
There's no "loss of oil" meter or anything. There's no way a pilot has to know how long the gas will drain from a tank or the oil from his engine before it's gone.
I'd rather it NOT tell how much oil time you have left. Already too many folks say "screw this, I'm going to keep dogfighting" and that would only give them reason to say "Fine, I have 1 minute left to fly, I'll dogfight for 59 seconds then bail"....
I think it'd set a bad precedent, personally.