Cruze’s New Oil Pump: Brilliant or Imbecilic?
September 8, 2010
Chevrolet has been trying to roll out the Chevy Volt; supposed MPG master of the road. Meanwhile it's sneaking out another contender in the fuel efficienct category: the Chevrolet Cruze. Gets great gas mileage (purported 40 mpg highway), looks cute (sort of like a civic), and so far looks nice and classy on the inside. Seems like Chevy is finally learning from Ford you need to have nice interiors to entice people. But more on that later.
Chevrolet is bragging about their new variable displacement oil pump. Most auto oil pumps use engine rpm to drive them and feed necessary oil to all the moving metal-on-metal parts in your engine. This could potentially mean you'd end up, at times, with the engine driving your oil pump higher than it needs to be for moments when you don't need to feed a lot of oil into your car. The idea with this pump is the oil pressure pushes the housing against a spring that when the oil pressure tries to go to a higher pressure than that of the spring it can't, reduces the displacement, and therefore reduces the oil pressure.
This isn't too much different from a standard oil pump where oil pressure increases with engine rpm. But in this case, load also has an affect thereby reducing oil efficiency even further. And by spending less of the engine power driving the pump, slight increase in mpg. However, to get this tradeoff is greater complexity. True, it's still hydraulically driven, but now requires nine spring-loaded vanes instead of just bypassing the excess oil like your typical oil pump.
Then again, it's not entirely new either. VW and Audi have been running similar designs for a while now, granted not on your "average" car like a Chevy Cruze. So, will it be a smart decision or a stupid one?