10% drop in Prius v mpg after new tires and fuel injector service

Your OEM tires probably had a different tread pattern, but the size is the right size. Brand new tires will cause you to have lower gas mileage initially, they need to be broken in for best mileage. This could take over a 1k miles or more, but it certainly should be broken in by 10k.

Your air pressure could be higher for better mpg, I have mine set at 44fr/42r. That's at the high end and will result in stiffer ride comfort. I have acclimated to this and it's a none issue. I get about 50mpg on the Bridgestone Ecopia EP422 I got from Costco.

The fuel injector and Throttle Body Service I've never had from the dealership, so I can't speak to that item.

Your drive pattern has also change from your previous pattern so that will have some affect on mileage. My driving is in the Houston metro area with a mix of freeway and suburban driving as a comparison.

 

Drop In MPG:

This is 0% fuel injection service related.

This is 100% new tire related.


Rob43

 

the fuel injection caused an unnecessary drop in your bank account

 

There is a coast down test that was detailed on this site that gives you sort of a ball park for rolling resistance. You accelerate to 60 and then time the coast down. You repeat the test three times in each direction on a deserted highway. Too bad that you weren't aware of it and performed it on the old tires and now the new tires to compare the results. Just noticed that the original post was in March of 2019.

 

@Ronald Doles could you post a link to the coast-down test?

 

Following for coast down test info.

 

I did a search and couldn't find the link on this website to the coastdown test. Here is one from GrassRootsMotorSports that is also an Excel spreadsheet.

 

The station wagon Prius is rated for something like 43/39...so your mileages aren't that bad but the change is something that bears investigating.
How many miles on the car in total?
Have you ever had the brakes worked on?

Advice:
1. Your tires are inflated to spec but there are some in the forum who advocate bumping them up about 5psi. If you have a pump at the house, it will not cost you anything to find out.
You might get some of the fuel efficiency back at the expense of a slightly harsher ride.
As mentioned above, the -3 delta is almost dead-bang guaranteed to be the tires.


B. I'm always VERY dubious about mechanics who prescribe car maintenance that's not in the warranty and maintenance guide.
If you trust them, that's fine but you're probably over-paying for their "help."
If you're close to your 120,000 maintenance then you may want to pay close attention to what they...ah....(*) "recommend" for maintenance.

It would be a shame to save all that gas money only to have to give it back to a dealer for unneeded maintenance expenses.....

 

I too experienced a drop in mpg in my 2016 prius after fuel injection cleaning. I was getting 56-61 mpg before the cleaning and it's been no higher than 50-51 effective immediately after the cleaning. New tires were installed 3 months before the cleaning. No significant change in weather, driving route or gas brand or tire pressure maintenance before/after the cleaning.

 

Regarding lower mpg aftwr fuel injectors ckeaned: I figured the injectors must be used to calculate mpg, since the injector cleaning was the only differing factor that occurred when I experienced the drop in mileage. When I googled i found this quote on Edmunds "senior manager of GM's energy center, explains that the fuel economy gauge makes a calculation by counting the number and duration of pulses made by the fuel injectors as they squirt gasoline into the combustion chambers of the engine. The onboard computer system divides the distance the car travels by this estimated fuel consumption." I know that's GM's explanation but im sure the manner of calculation is global.
Edmunds had that reply to their questions to manufacturers as to why their manual mpg calculations were consistently, significantly lower than the tested cars' computed calculations.
I've long suspected the car's calculation was faulty. Sometimes I've cranked the car and noticed the displayed mpg was 199 or 99, which rapidly adjusted down after driving a few miles. I'm disappointed in the automotive industry, but Yeah. Welcome to reality. And Santa Claus isn't real either