At around 35k, my 2017 Prius MPG dropped from 60-65mpg to 47mpg. I've been into extreme car modification for decades and I thought this would be a simple fix. I live in Socal and the weather only fluctuates from 65-85 on average. I started with the simple fixes first - reflash the ecu, check the tire pressure. Nothing. Rubbed my chin and took it to a tire shop and got a rotation. Still no change in MPG. Ok.. so I took it up a notch. Replace the air filter with K&N.. nope. Replace the cabin filter.. nada. wth. Nothing installed on the exterior to create wind-drag. I was frustrated at this point and took it up another notch. Replace the 12v battery with a brand new one from the Toyota dealer. This is usually the last step for many and often times it fixes the issue. For me, still nothing. I didn't notice any difference in the frequency of engine kicking in. I believe in 'if you throw enough money at it, you can fix the problem.' So I went and replaced all 4 tires (my treads were at 20%, but had some cracks on the walls). This still didn't fix the issues. My last ditch effort was to clean the fuel injectors. Still didn't change anything. I swallowed my pride and started digging deep into the forums for answers at this point, but still couldn't find anything worth while. So exchanged it for a 2022 Prime XLE, lol. I work from home, so I'll be filling up around 5x times a year. With a $6.50 average gas price in socal, this is awesome. Here's a check list for MPG drop. for 90% of you, one of this will solve your issue. Order from simple to more aggressive. - Check Tire Pressure - Rotate tires - Temp drop or fluctuation? - Elevation change? - States with extreme weather - try thinner synthetic oil in the winter and thicker in the summer - disconnect the battery to have your ecu re learn your driving habit - Change air filter. Change cabin filter - Newly installed roof rack or other culprit of wind-drag - Change all 4 tires - Change the 12v battery (often times this fixes the issue) - Clean the fuel injectors (not using injector cleaning solutions, but having the shop clean it) desperate attempts - replace transmission oil (dirty oil can interfere with shifting) - clean or replace O2 and MAF sensors - change spark plugs. - clean throttle body very lastly, it can be your electronics, which isn't common.
Also, running AC will hurt MPG by 3-5, but not by 10+. There's a small possibility that my main battery was wearing out, but it only had 35k miles.
Years ago, I asked a Toyota mechanic about using fuel injector cleaners in my vehicles. He said I don't have to worry about that if I use gasoline from "Top Tier" gas stations. There's one near me so, now, I only fill-up from there, even if their price is a bit higher (it usually isn't, though). This website helps you find Top Tier stations and there's even an APP for your phone you can download. https://stationfinder.toptiergas.com/
Yep, you are right . Just changed my Écopia for 4 winter tires and steel wheel for winter (mandatory where I live for the 1 december) and got a 10% dip in my EV range.
I'm going through the same exact issue as you.. Tried all the above EXCEPT cleaning out the MAF sensor and hoping thatll fix it. Its a 2016 with 133k+ miles so my other thought is the hybrid battery giving out but i'm hesitant on believing it because of the long term durability of it reported by others..
