Crosstrek: CVT vs manual 6x

[ditzaroo]

I'm trying to understand why the '18 crosstrek equipped with a CVT gets 3MPG more than the same model equipped with a manual transmission.  I thought it was natural variability in driving patterns with a manual transmission.  But just the other day I came across a post on reddit saying that the camshafts in that model are ground specially for the CVT shifting in mind.  The engine runs smoother at consistently lower RPM and that's what makes the CVT design get better mileage than the manual.  Also, there is less oil blow-by since downshift breaking is minimized with the CVT (I also heard that the rings are thinner to reduce friction and increase mileage).  The thing is, I haven't heard anything about this anywhere else.  Can someone on this forum confirm or deny this? 

 

[987687]

I don't know about the specifics you mentioned, however a CVT is pretty much always going to get better mileage than a manual. It has a much wider gear ratio and can change gear ratios very quickly. This means cruising on the highway the engine can be running a very, very low RPM, but move to a lower gear ratio to make it up an incline. With a manual transmission you can't have a really tall overdrive gear because you'd constantly have to be shifting out of it, lugging the engine, etc.

Same with stop-and-go traffic, the CVT can keep the engine at a much lower speed accelerating slowly. With a clutch you continuously have to rev the engine to get it first gear, then rev it out far enough to shift into 2nd without lugging the engine, the CVT has none of these restrictions.

 

I wouldn't be surprised if the engine was tuned differently with a different cam profile. It's driving a somewhat different load, so Subaru probably fine tuned it to match that load. The engine computer and transmission computer can work together for the most efficient driving, whereas a manual needs to be tuned for someone who may not be good at driving a stick. 

[djbroadus]

I drove a 18 6 spd about a week ago, was pretty disappointed with the road and engine noise. The gear box felt really sloppy and cheap compared to my old sti 6 speed. CVT may be the way to go imho.

Edited October 3, 2017 by djbroadus