Questions on cooler weather behavior.

My daily commute on US 26 takes me over Portland’s Sylvan hill with a vertical of in excess of 500 feet. With the traffic usually slowing from highway speeds at the top to near stop-and-go at the bottom in both directions, it is a near daily occurrence for me to see a full green bars on my battery level display.

Normally, I have been able to drive quite a distance through traffic without the ICE restarting after this descent. Recently, I’ve noticed a tendency for the ICE to stop and restart a number of times, not only after leveling out, but while still descending with my foot off of the accelerator. With the weather turning colder recently, I was able to duplicate this behavior with the heat and defroster both turned off.

I am thinking that with the cooler weather (low-40’s to mid-50’s), the ICE is being restarted to warm the more rapidly cooling engine (??). With the occasional traffic slowdown, I have spent as much as 20 minutes without needing to restart the ICE in the past.

In addition, I pulled into my regular gas station to refill this morning. Out of sheer habit, I normally pull up to the same pump at the same gas station with the same attendant (Oregon is one of the few states with no self-service gas pumps). As I normally fill up at around 2-3 bars, I was expecting to take around 7-8 gallons as I have for the last 18 tanks. To my shock, the pump charged right past 8.7 gallons before clicking off as fuel shot back out of the tank.

I’ve heard of others experiencing this but, until now, I have never encountered any issues with tank spit-back, inability to fill the tank or drastic inconsistencies of the fuel gauge. Since Oregon does not have any self-service pumps, I was not paying attention to what setting the pump was on. After calculating my MPG and comparing it to my displayed MPG, I’m assuming that I took at least 1-1.5 gallons more than I normally would have from this same pump. The VIN for my Prius is outside the range for the EL010-04 TSB. Needless to say, my calculated MPG has dropped dramatically from around 52 to just under 40 mpg.

With my beloved Prius performing so well over the last 4 months, I’m left wondering if it has suddenly become possessed?