# Gas mileage **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** hybrid-repair, chevrolet, 1500\ **Created:** [July 13, 2010, 4:16am UTC](https://community.cartalk.com/t/gas-mileage/51754 "2010-07-13T04:16:48Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![jmnewton](https://avatars.discourse-cdn.com/v4/letter/j/ed655f/32.png) [@jmnewton](https://community.cartalk.com/u/jmnewton)\ **Post date:** [July 13, 2010, 4:16am UTC](https://community.cartalk.com/t/gas-mileage/51754/1 "2010-07-13T04:16:48Z")
I recently replaced lifters on 2007 1500 chevrolet with cylinder deactivation. I now get 4 mpg less than before replacing lifters. Any suggestions? ---
**Author:** ![jmnewton](https://avatars.discourse-cdn.com/v4/letter/j/ed655f/32.png) [@jmnewton](https://community.cartalk.com/u/jmnewton)\ **Post date:** [July 13, 2010, 4:20am UTC](https://community.cartalk.com/t/gas-mileage/51754/2 "2010-07-13T04:20:26Z")
not a hybrid ---
**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\ **Post date:** [July 13, 2010, 12:44pm UTC](https://community.cartalk.com/t/gas-mileage/51754/3 "2010-07-13T12:44:12Z")
Why did you need to replace the lifters? ---
**Author:** ![jmnewton](https://avatars.discourse-cdn.com/v4/letter/j/ed655f/32.png) [@jmnewton](https://community.cartalk.com/u/jmnewton)\ **Post date:** [July 15, 2010, 7:43pm UTC](https://community.cartalk.com/t/gas-mileage/51754/4 "2010-07-15T19:43:06Z")
lifters collapsed due to cylinder deactivation this is a bad problem chevrolet is having just dont know why it would hurt gas mileage so bad ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [July 15, 2010, 9:02pm UTC](https://community.cartalk.com/t/gas-mileage/51754/5 "2010-07-15T21:02:04Z")
Are they hydraulic lifters? Mostly I smell a coincidence. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [July 15, 2010, 9:40pm UTC](https://community.cartalk.com/t/gas-mileage/51754/6 "2010-07-15T21:40:46Z")
I’d be inclined to want to put a vacuum gage on the engine, deactivate the “displacement on demand” system, and see if the vacuum is steady. It may be that the cylinders remaining closed is allowing a residue that’s gumming the valves. The crankshaft and its connected components do continue operating, so the walls continue to be bathed in oil but residue never cooked away as it would be in the combustion process, causing a gumming of the walls of the cylinders and the valve faces. Remember that the engine ovverall is still at operating temp and those cylinder walls are still hot, albiet not as hot as if they were experiencing combustion. Understand that I’m throwing a wild guess on the table. I’m sure the problem is more complicated as it’s looked into more deeply. But my guts tells me valves may be sticking. Wayyyyyyyy back when we had a lengthy thread on this subject. It was my feeling then that this system would not come without some problems. Perhaps my suspicion has become reality. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [July 15, 2010, 9:56pm UTC](https://community.cartalk.com/t/gas-mileage/51754/7 "2010-07-15T21:56:43Z")
"Wayyyyyyyy back when we had a lengthy thread on this subject. It was my feeling then that this system would not come without some problems. Perhaps my suspicion has become reality. " It never worked. It never will work. GM needs to learn how to fire losers who call themselves “engineers”… ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [July 15, 2010, 10:35pm UTC](https://community.cartalk.com/t/gas-mileage/51754/8 "2010-07-15T22:35:03Z")
Or stop using their customers to do their long term reliability testing for them.