Did reprogram affect your mileage?

[Azor]

Originally posted by earnyermoney@Feb 27 2006, 05:13 PM
Every time I take my 05 Prius in for a 5K checkup, the gas milage has gotten worse.

I have also had large discrepancies between the cars calculation of MPG and the manual calculation based on the miles driven divided by the gallons added to the tank. The diff between the two methods is over 20 MPG. Piss poor. You simply can not trust the fuel gauge on the dashboard.

[snapback]217610[/snapback]

Just to clarify: ALL the gas mileage I have quoted in my thread of conversation comes from me filling up the gas tank to the very tippy top and then dividing the miles I have driven since the last tippy top tank by the gallons I just put in. I have never relied on any display. Of course, I continued to calculate mileage the exact same way after the reprogram and got significantly lower mpg.

[Azor]

By lengthening the duration to, say, 0.4 seconds, the reprogramming will avoid the "false alarm shutdown." The actual conditions under which the ICE starts up are not changed, just the "patience" of the car as it waits for the ICE to fire.

[snapback]217621[/snapback]

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Do you think this duration lengthening could decrease mileage for someone who got good mileage to begin with because of their "patient use" of the gas pedal? I did all the tricks to increase the mileage...

[Tideland Prius]

No but it could increase the amt. of fuel left before the light comes on so you'd travel less before the last bar blinks and also fill up less.

[artie]

My mpg was reduced a bit after the campaign. maybe not so bad now, i am able to avge. 50 plus on the hwy, but i have to drive slower, 64 or 63 mph.

[robinsod]

I have noticed no change since the reprogramming. I understand the reason for the reprogramming was that with some '04's the ICE would shutdown and not restart as it should have. I had this happen once. (It finally restarted after a several minute wait with the car powered off.)

If the mpg drops after servicing, I would suspect an oil over-fill problem.

Also, after a tire rotation, you may find that the tire pressure is not what you usually maintain.

I agree that a large (10-20mpg) drop after the reprogram suggest a malfunction. I'd insist on another reprogram.

[Azor]

Thanks to everyone for all the info.

I'm pretty sure I won't be able to get the old program back. I will definitely try for another reprogram (I just hope things don't get worse than they are now). At the least, I'm hoping Toyota pays for this reprogram. I also think they should warn those that have not upgraded their old program that there is a pretty good chance mileage will decrease.

For those mentioning the oil - I had no oil service. Therefore, oil overfill is not the issue.

For the note about more fuel remaining in the tank - that would make no difference in my mpg calculation because I use an accurate method that does not rely on displays: I fill the gas tank to the top and divide the miles since the last full tank by the gallons inserted in the new full tank.

The issue is that I observed the engine acting differently after the reprogram. For example, on this stretch of highway that gently sloped downward I could release the gas which would shut the gas engine off. Then I would coast on battery and then ever so gently press the gas to trip the electric motor. I could go on electric for 2 miles or so at speeds over 50 mpg. Now, no matter how hard I try, the car will not allow me to do this on the exact same stretch of highway. The engine always kicks on when I gently press the gas. The electric coasting was something I did consistently for 2 years on my way to work. The reprogram no longer allows this resulting in a significant decrease in my mileage.

[V8Cobrakid]

i hope it doesn't do what lexus put into their programing.. with the 400h, you get three tries for the ICE to fire.. if it doesn't fire, then it locks out.. and you have to take it to a dealer.. so i plan on testing this with our 400h?.. no..

[Tideland Prius]

By "top" you mean filling until you see fuel? cause when the pump clicks off can vary too.

[tomdeimos]

Already posted here my results. Get way better mpg with the reprogrammed computers.
Very glad I got it done and early.

[HybridVigor]

I believe that my dealer performed this upgrade on my car during my 5K oil change/service. I also saw a change in mileage but only on the MFD. By this I mean, my MFD mileage dropped by several miles per gallon, but my calculated mileage based on miles driven divided by gallons pumped stayed approximately the same as before. I have not noticed any difference in when glide can or cannot happen. Driving behavior seems about the same. In the end, this has been a good thing because my MFD mileage was consistently 2-4 mpg too high, and the update brought it closer to my calculated mileage.

One item of note: When the dealer did my service, they identified that my tires were set at 38/40 (or whatever the hell I had them at) and reset the pressures to Toyota specified numbers. This temporarily drove me batty until some kind soul here suggested checking them, and I was able to bump them back to 40/42. Perhaps part of the problem some folks are having might be related to lower tire pressure?