FearlessFarris

I know that having my performance exhaust turned on may inspire me to be a little more heavy on the pedal, but I'm curious if--all else being equal--the performance exhaust settings actually make any difference in the overall fuel efficiency of the vehicle?

FLC63s

Most definitely effects gas MPG....

Tuxdude

If the performance exhaust only affects opening/closing the valve, does it still affect mpg? If it causes the engine to rev higher than when the perf exhaust is turned off, then yes for mpg decrease.

FearlessFarris

Yes, you restated my original question better than I did, thank you.

I don't believe hitting the PE button changes how the engine revs (whereas switching to Sports Mode does change the revs). It mostly has to do with the valves, from my understanding. Correct me if I have this wrong.

So, all else (including revs) being equal, does activating PE decrease MPG?

untamedd

Opening/closing valves will make no difference to mpg. Opening the valves and driving aggressively to hear that intoxicating sound definitely will.

You should know that this car is obviously not gas friendly. For eg. I filled her up and drove around in Race mode for around 100 km and the tank was almost half gone lol

FLC63s

I believe that since opening/closing the valves the back pressure, you will get a variance in MPG..
(its not as drastic as changing from Comfort to Sport mode of course) but still effects to a degree) <- from my experience ...

I have aftermarket exhaust on mine, so cannot really speak in terms of stock cars...

munis

Talking about fuel economy in the C63s section ? Just kidding. I think yes the PE does affect the mpg as burble over runs are added only when PE is activated. Overruns and burbles do waste gas more gas than just driving it normally.

LessIsMore

In theory the open valves would allow gasses to flow more freely, which would actually improve MPG. Although probably not noticeably. Realistically, I think the practical effect will be that most people will have a heavier foot with it open and thus correlate to lower miles per gallon.

superstarR

PE exhaust is usually on and I’m getting 8 MPG with a mix of S+ and C driving. I fuel about every 3 days.

user33

My individual mode setting has powertrain in Sport mode and the PE on. I use an app to keep track of fuel mileage. My 2017 C63 S sedan's mileage has varied from 21.14 MPG (Imperial gallons!) with mixed highway/city driving (I'd guess 60/40, no long highway trips yet) down to 4.63 MPG during about 50 miles of on-track driving. From the trip computer, it looks like the "highway only" mileage is about 25-26 MPG ... giving this vehicle a _huge_ dynamic range of more than 5:1 (thank you modern ICE technology).

As others have stated, I suspect the PE, itself, has no effect on fuel mileage (but does affect "fool [around] mileage").

Mojo31

Does it really matter? I don't think anyone would buy one of these to hypermile with the Prius set.

FearlessFarris

I'm not one of those guys who tries to squeeze every last MPG out of my vehicle, but I do like to understand my vehicles as well as I can. It's more a question of curiosity than any real concern about optimizing mileage.