I have read the gas mileage pdf. I'm wondering why my 2010 Prius has dropped about 5 mph over the past 2-3 years. Some of this may be due to more short trips however long highway trips are also about 5mpg lower than in the past when I got over 50 mpg (currently getting about 45 mpg on the highway, 40 in town). These mpg numbers are taken from the read out on the dash. Here's more info: 2010 Prius 3 with 122,000 miles. Bought it 10 years ago when it had 40k miles. I have changed the oil with 0w-20 full synthetic every 5k miles. Changed trans fluid at 97,000 mi. Last replaced air filter at 120,000mi. All other fluids are original (I plan to change them this Spring). Spark plugs are original (need changed). Replaced brake pads and rotors and bled brake lines several times; there are no dragging brakes. Replaced a rear wheel hub 4 months ago. I run Costco top tier gas 90 percent of the time (87 octane). I did a DrPrius test of the traction battery today and it came out as 'good' at 83.5%. I replaced the 12v battery 2 years ago. It has never had a check engine light or error code. Car seems to run perfectly as it always has. Acceleration is strong, no bogging or hesitation. Since the traction battery is okay, I'm wondering the the most likely culprit is the EGR valve, which has never been cleaned. Please let me know what you think. Thanks.
Not sure that it'd be the "culprit" for mpg drop, but definitely get on cleaning EGR ASAP. Any recent tire replacement?
I feel it's good to monitor mpgs; could be the canary in the coal mine. Unfortunately, hard to isolate factors that affect it, especially going back 3 years, without super detailed records. Sounds like something changed in the way you drove it though, with the 'shorter trips', unless it was external. Mpg is highly dependent on speed. Something changed. I wouldn't trust the computer for an accurate measure. I don't know how it calculates-perhaps integrating instantaneous usage? I wonder if the computer readouts remain constant over time, as in, say, 'always 2 mpg optimistic', or does that change over time? How about tires? Trying to think of something that might not be in the .pdf...
It dances around some, I would think mostly due to vagaries of gas station pump shut-off, but stays about the same on average. My take, it’s almost certainly an intentional “tweak” by Toyota.
I realize that. I just wondered if any changes could be attributed to sensor deterioration over time.
