# Why is my hybrid mpg getting worse with time? **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** hybrid-repair, fuel-economy, camry\ **Created:** [April 27, 2008, 5:47am UTC](https://community.cartalk.com/t/why-is-my-hybrid-mpg-getting-worse-with-time/13322 "2008-04-27T05:47:49Z")\ **Posts on this page:** 2\ **Page:** 2
**Author:** ![J.D.Bookhout](https://avatars.discourse-cdn.com/v4/letter/j/59ef9b/32.png) [@J.D.Bookhout](https://community.cartalk.com/u/J.D.Bookhout)\ **Post date:** [April 30, 2008, 6:19am UTC](https://community.cartalk.com/t/why-is-my-hybrid-mpg-getting-worse-with-time/13322/21 "2008-04-30T06:19:23Z")
I don’t have specific knowlege of your car but I do believe that the most commonly overlooked engine maintainence is valve clearences.Find a mechanic that has the shims and have them set on the loose side of specifications. ---
**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\ **Post date:** [April 30, 2008, 10:54am UTC](https://community.cartalk.com/t/why-is-my-hybrid-mpg-getting-worse-with-time/13322/22 "2008-04-30T10:54:16Z")
“Would the change in fuel mixture show as a gradual chance in mpg on an instantaneous (per fillup) mpg chart, or would it be more of a sudden change with a standard range for winter and summer?” Yes … Generally it will change over a matter of weeks. The tank at the station will not be empty when the new fuel is added so it becomes a blend. Even the fuel being delivered can be a blend from the tank farm. So it does change, but it should not take too long to be mostly changed out, a few weeks likely. It is also possible that they may intentionally have an intermediate mix, but I don’t know if they do that anywhere. [Previous page](https://community.cartalk.com/t/why-is-my-hybrid-mpg-getting-worse-with-time/13322.md?page=1)