Soo according to my MPG read out on the last two long road trips I've done (Houston to Austin, Austin to Houston) I got about 23ish on both trips. The first trip I did the day after having the stillen cat-back installed. The most recent trip was today, about 3 weeks afterwards. Usually I averaged mid 19s/low 20s on the drive - is it completely possible that freeing up the exhaust system gave me 3(ish) more MPG in this situation? Similar driving style, similar speed, etc?

 

it's possible the exhaust helped your MPG, but it's also possible it's just the speed/traffic that you had. B/c i drive roughly 70-80 miles a day, and it varies so much on the traffic and how i drive my car. I'd range anywhere between 19-25mpg... and I reset my MPG calc after every fill up. But if i get caught in a lot of red lights on my way to get to the interstate, i'd never get past 20mpg. But if its a fairly smooth trip to get to the interstate for me, i'd average ~22-23 MPG driving fairly quick on the interstate (~85mph). But if there's congestion on the interstate and it makes me drive 60, i get like 25 mpg...

 

I am seeing about a 2.3MPG increase since installing the Stillen exhaust on my car. When I first got it, I saw about a 4MPG decrease, but that was because I couldn't keep my damned foot off the gas. In all seriousness, I've seen huge MPG gains on the highway and city.

 

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The drive from Houston to Austin is about 160ish? miles and 98% of that is spent at speed (there's all of 3 stop lights along the way) so the speed driven and style driven was about the same. I have to make the drive again tomorrow so I'll update with the mileage that way. But as I said, all trips are done at similar speeds with similar driving conditions and it's over such a large distance that the 3 stoplights don't really factor in.


Nice! I'd confidently say it could add 10% to the mileage. If you're getting 2.3 and I think I'm around three. They should test and advertise this too!

I completely agree though - I spend ALL my time listening to the exhaust. I always make sure to downshift when slowing down to get that little kick in the exhaust. I'd have to say my mileage has for sure dipped around town cuz of how I drive now, but on the highway it seems up!

 

To get 3mpg more with all things equal except the exhaust, you'd have to be making significantly more hp at highway speeds with the same throttle. Our exhausts aren't restrictive enough for this to be the case.

Most likely weather conditions along with the other usual variables like traffic.

If the DA was better that day you'll have seen better mpg.