[Shop-talk] How do they do that?

[Eric Murray]

On Sun, Apr 11, 2010 at 04:21:38PM -0400, Gerald Brazil wrote:
> So listers, how does the car's computer system immediately recognize that I
> have just dumped in a load of higher octane gas?

If that is what is happening, it could be because the ECU isn't having
to pull timing advance to prevent knock.  There is usually less BTUs
in higher octane pump gas, but the tuning of a particular engine can
make more difference.  On your engine and car, high octane apparently
improves mileage significantly.


OTOH, the car is guessing that you filled up the tank.  It can't measure
the input to the tank, only the outflow.  So it is possible that it is
underestimating the amount of fuel you put in.

Eric