Balancing Act

Observed Increase in Fuel Efficiency For the 2012 Prius Follow Up

Here’s a follow up to the original post regarding fuel efficiency improvements after performing major maintenance services. In addition to the following services,

I recently cleaned the throttle body, the intake manifold and mass airflow sensor at 124,990 miles. I’ve also changed the motor oil and replaced with 5w-30 viscosity Mobil 1 High Mileage motor oil. Since these additional services, I have driven an additional 1,000 miles and have seen a significant boost in fuel efficiency. I gauge the Prius’ fuel efficiency from two indicators:

  1. the MPG as reported by the Hybrid System Indicator (HSI)
  2. the cruising range until empty indicator

For the past three years, I have watched the Prius’ system reported total cruising range, after a full tank, gradually decrease from ~590 (at the start of ownership in May 2012) to ~480, to ~420 and rock bottom at 385 miles.

After performing the above bullet points of maintenance, I’ve seen the total cruising range increase back to 416 from ~385 after filling up a full tank. After changing the motor oil (to 5w-30) and cleaning the intake manifold, throttle body and mass airflow sensor, not only is the Prius hitting the mid 50’s in MPG average fuel efficiency between fill-ups¬†consistently¬†for the first time in at least two years, the total cruising range also jumped to 587 miles, very close to the initial ownership era.

Also, the first thing I noticed is that the EV indicator activates with more frequency when I’m cruising at 45 mph or slower. Before, I would had to “ease” the throttle to trigger the EV assist, but after doing the aforementioned additional service, the EV assist just activates with higher frequency.

I was literally blown away by this significant jump. This weekend, I will fully service and clean the entire exhaust gas re-circulation (EGR) assembly, including the cooler. I am estimating the entire job will take at least 3-4 hours but I am eager to see what, if any, improvement it has on further increasing the efficiency of the Prius.

We’ll be taking the Prius on a road trip to Sonoma County soon, so this will be the perfect time to gauge any improvements, if any.

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