Winter gas and fuel trims

I reset the mpg history each summer/winter. Is this what your talking about?

 

not that i have ever read

 

I think OP means to disconnect the 12 volt neg cable for a minute or so.

I've done that when doing brake work, and the next few start ups (two or three), it does an unusual rev-up, for maybe 15 seconds. I'm thinking it's testing something, re-establishing some parameters.

My 2 cents, I wouldn't bother doing this seasonally, but who knows.

 

Ignore the MDF.
Those values are only useful as an 'is/was' indication for relative fuel efficiency.
The computer values are off by at least 3-percent.

If you've changed wheel/tires then you're going to see a change in your fuel efficiency. That change will be reflected more or less as inaccurately by the MDF whether or not you 'reset the computer.'
If I understand the ECU's role in dolling out gas to each of the four cylinders, I'm not sure what resetting it will accomplish other than to erase the information stored from the 'summer gas' use history.
The only 'learning' that happens from what I remember is the DTE (distance to empty) guestimations which are updated by historical fuel efficiency guestimations.

Either way, your car's 'real world' fuel efficiencies are not going to be affected by resetting the ECU if I understand life in Priuses correctly....whether or not your local fuel supplier has started diddling with your local formula.

Does this happen on a specific date in Caly?
Do they drain the tanks first or is the summer gas allowed to mix with the winter gas briefly?

Winter versus Summer blends in the south east must not be that big a deal, because I never hear it discussed other than in this forum.....but my tank-to-tank averages in winter change more from temperature variations than fuel blends - and even then not by that much.

 

Turn around is just an industry term for shutdown.

They do a lot of repairs as downtime is $$$.

I know the labor pool is thin up here as the turnarounds are happening.

Not related to answer you question I would say though.

 

there must be a required date in the law, but who knows when it gets to a gas station?