Gas mileage

hybrid-repair
chevrolet
1500

#1

I recently replaced lifters on 2007 1500 chevrolet with cylinder deactivation. I now get 4 mpg less than before replacing lifters. Any suggestions?


#2

not a hybrid


#3

Why did you need to replace the lifters?


#4

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


#5

Are they hydraulic lifters?

Mostly I smell a coincidence.


#6

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.


#7

"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”…


#8

Or stop using their customers to do their long term reliability testing for them.