More than a 20% drop just due to tires? And the OP said he bought fuel saver tires? Got to be something else. Granted maybe the new tires may cause some loss, but this loss is really significant. I would go over the whole car, check the normal stuff or have Toyota do it. That much of a drop is really high. Rocketman
I vote for temperature. The mileage on my hybrid drops about 7 mpg or more in winter.
Any chance this could be an electronic hiccup affecting the dashboard indicator?
The MPG display on my Lincolns has been near dead on but now and then (say once a year) it has a tendency to go off the rails for a day; maybe two.
The car usually gets about 27.5 on the road and when it develops a hiccup it may show 16, 19, or whatever. A day or two of that anomaly and then it’s back to normal.
Of curse we have no idea how OP measures his gas mileage. I once heard the owner of a Ram truck brag he got 35 mpg.
In the late 80’s, I was driving a used Bonneville, I think 8 pass. I got around 17 mpg out on the open highway. A fellow worker ridiculed md and said the same model gave him more like 24 mpg. I did not believe him.
Docnick, I measure using Fuelly app which gives me accurate mpg than my car’s display does.
Not sure how an APP can measure mpg. The only sure way is to fill the tank to the FIRST click, then drive till it’s less than 1/4 and the fill it up again TO THE FIRST CLICK AT THE EXACT SAME GAS PUMP!!!
Do this twice and you will have a reasonably accurate figure for mpg. Depending on you driving, the second tank may yield a different figure, so it’s best to average the two.
I agree, I don’t see how any app can accurately measure MPG. It doesn’t have the data. Unless you are doing like Docnick states above, in which case it’s just simple arithmetic and you don’t need an app to do that. Or I hope you don’t.
I don’t think you have to go back the the same pump, they are accurate enough.
Pretty sure the app requires you to put in miles and gallons. It’s a way to track and compare mpgs.
@texases Yep, Always input mileage, price input and exact gallons filled up with that app.
Oooooo—you mean the app will divide for you? Wow! Where can I get one??
Lost 2 mpg, 18 to 16 city, 24 to 22 mpg hwy after switching tires, were Michelin cross terrain to long trail ta, never got it back, gas usage and mileage, same tire size.
Just because they’re labeled “fuel saver” does not mean they’re meant specifically for super dooper fuel efficient hybrid vehicles :neutral:
Big difference, as was already pointed out
Nobody’s going to market tires that say “gas guzzler” on the sidewalls. Can’t imagine too many people would buy them, if they saw that 
It’s like buying a brake pad that’s labeled “ultra premium” 
Fine . . . doesn’t really mean they’re quiet, doesn’t mean your car will stop on a dime, doesn’t mean the pads won’t eat up your rotors 
OP, please answer these previously asked questions:
Did you get the “Energy Saver” or the “Energy Saver A/S”?
(TireRack lists your A/S at $122/tire. What did you pay?)
Did you get an alignment with the new tires?
So this “fuelly app” is really just a calculator? It just also keeps rack of how much you paid for the gas. No wonder it is fairly accurate.
@melott if you have iPhone, go and download free app “GasTracker+” which is Fuelly connected you can see on web browser on PC.
I’m not sure if they have app for Android devices
@MikeTheMailman please look up “sarcasm”
@BillRussell That’s probably true for NEW pumps. However at my favorite gas bar some pumps click off much earlier than others. The difference may not be large compared to a full tank.
A $10 pocket calculator is all you need to get accurate gas mileage. The local DMV here has a handy little cardboard slide rule where you dial in the miles driven and gas consumed and it gives you the mpg.
That’s true, doc.
IMHO mileage should always be calculated over a number of fills rather than a single one. Even then it’ll never be perfect, but the inaccuracy won’t be large enough to be important.
Even if the pumps were perfect and the odometer accurate, there’ll still be variations in mileage due to weather (including wind), road conditions, length of drives included, and other variables. But monitoring mileage will tell you when you have a problem. When it drops significantly outside the normal variation, it’s time to take a look. Of unhitch the boat from the bumper hitch.
@mountainbike Very true. I average 3 tanks or so to get a representative figure. The best mileage is always on a long trip at moderate speed.