drastic reduction in mileage after tune up

[syncmax]

I took my car for a problem I have always had with this car - rumbling noise at most speeds esp at highway speeds. They have done front wheel alignment twice before - they told me my tires were cupped - uneven wearing. Finally I got sick of the noise and at 65K miles I was ready for change of tires. There was still good tread left on factory original tires. They replaced the tires with pirelli centurato all season - which is what they said they were putting on all cars (the original dealer we bought car from). They also called me and said the car was due for tune up service - I said go ahead. This involved new spark plugs and the invoice indicated them updating PCM software to the latest version. After I took the car back I felt the ICE was kicking in more often than before. Sure enough after two tanks of gas I realized my mileage has gone down from 45-47 before to 40-41. It was roughly 50:50 split between EV miles and non-EV miles before. Now it was more like 25:75 (EV:ICE). I called them and they said none of the work they did has any impact on it. I probably should not have replaced the tires at the same time as doing the tune up. Now I don't know which one of this is the culprit. any thoughts?

[jestevens]

Do you have to step on the gas (ICE) to get it to move all the time?  Hybrid cars need low rolling resistance tires, period.  Without them you won't be able to do all of the coasting that is necessary to save gas. 

 

There are multiple versions of the P7 tire.  "Pirelli Cinturato P7 All Season Plus" and "All Season" (A touring tire, $150 or $174 on tire rack) have their "EcoImpact" formulation.  I had a set of the P7's and although they were "stickier" than the other tires I found that to be helpful in wet/snow weather so I grumbled a little bit and kept them anyway until they wore out.  With the OEM tires the car was reporting around 45MPG average.  My average MPG when I switched to the P7s and ever since really has been about 40.2 with tires at 42 psi.  On individual trips I range from 37-60MPG - depending on ambient temp, engine temp, traffic, use of EV+ around town, etc.

 

The local dealership recommended Goodyear fuel max assurance tires and they seem like a good tradeoff between price and performance.

 

I find that LRR tires already start out at 7/10th brand new, so although I don't seem to put that many miles on I go through one set of tires a year anyway, maybe I like the electric torque too much.

 

It may be that brand new they are very sticky, and once they get broken in your mileage may get slightly better.

 

One time just starting out with hybrid I was stupid and decided to put standard BF Goodrich Traction T/A tires on my Prius because I didn't know just how much difference LRR tires make.  HUGE mistake, every time you step on gas engine comes on (the horror!).  I took them back to shop immediately and very lucky they were willing to swap them for LRR without any additional fees.

Edited October 4, 2019 by jestevens

[plus 3 golfer]

1) new tires get about 2% less in FE than old tires due to increase in diameter vs old resulting in odometer recording less miles traveled with new tires than old tires.

2) new tires will have higher rolling resistance than when the new tires are worn assume 20% or a 2% reduction in FE.

3) if old tires were the Michelin Energy Saver, then the RR of the new tires is significantly worse than the E/S. See this chart in link below which shows your RR force at 8.8 pounds which is good but the E/S are likely around 8 pounds or lower, say around 10% lower which equates to around a 1% reduction in FE.

4) inflation pressure affects RR and the effect will be different on different brands.

 

So, it wouldn’t surprise me if the new tires have lowered FE by 5% or more. Colder weather will require ICE to run longer to reach operating temperature. Colder weather means the air is denser and increases aerodynamic drag lowering FE. Dealer will set tire pressure at the pressure on the door jam. Increase your tire pressure. The linked thread talks about tire pressure.

 

http://fordcmaxhybridforum.com/topic/7794-figuring-out-the-right-tire-pressure-to-use/?p=73572

Edited October 4, 2019 by Plus 3 Golfer

[ptjones]

I agree with above comments, Michelin's get the best MPG's so any other tire your gas mileage will go down. :sad:

 

Paul