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2016 EBPP with 54k miles, bone stock motor. New block and head with 1k miles accrued so far. Both before and after the new motor, my display has always said I average about 23.x mpg. I do about 65 highway, 35 city. I was expecting around 25-26 mpg, but figured the 3.55 gears aren't doing me any favors there and I've been "breaking" in the block so I'm varying rpm quite frequently and not necessary focused on mpg. Now that I'm past that period, I'm driving more normal, but still not impressed by the mpg. I drove about an hour yesterday, all freeway, and intentionally kept it around 65-75 tops. That yielded me a max of 27.8 mpg over the course of the trip.

I've seen plenty of people in other posts saying they're getting 30-35+ mpg during highway driving...are these people driving 50 on the highway or what am I missing here? Are these motors really that finicky or are they really all over the board?

I very rarely see boost as well, it's not like I have a heavy foot. The only thing I know was affecting it was it was 100+ degrees and of course the a/c was on. I'd expect a couple mpg increase in better weather with no a/c on, so maybe I need to wait for cooler weather before I start complaining...lol
2017 EB convertible, 3:55 gear, 6 spd auto, using 93 oct gas from Costco, stock. Have averaged 28 mpg for 38K miles. Interstate gets low 30's consistently running 65-70 mph. Have gotten as much as 35 on a long flat interstate run at 65 mph.
 

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2017 EB convertible, 3:55 gear, 6 spd auto, using 93 oct gas from Costco, stock. Have averaged 28 mpg for 38K miles. Interstate gets low 30's consistently running 65-70 mph. Have gotten as much as 35 on a long flat interstate run at 65 mph.

Your numbers fall right in line with me. I do 65-70mph all day, and im 3.31 so add 3-4mpg on top of your mileage for my gearing and speeds and we are right in line.
 

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Discussion Starter #23
Any of you guys have a FP tune? Wondering if that affects it much. I was seeing the same ~28 mpg on a relatively flat road at 70-75 without a/c on the other day, just really seems low for some reason. I'm not going to stress about it, but damn lol
 

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Any of you guys have a FP tune? Wondering if that affects it much. I was seeing the same ~28 mpg on a relatively flat road at 70-75 without a/c on the other day, just really seems low for some reason. I'm not going to stress about it, but damn lol
yes. I do. I always got 30-35mpg on highway at 65-70 though (but I dont really use ac) I keep windows down and use AC seats, Lol I just like it during summer.

but I already gained some MPGS after catted downpipe install, just a couple mpg, like 2-3
(full 3 inch downpipe, into 3 inch exhaust into 2.5 inch duals) so no restrictions I guess other than the small cat. I assume this lets it breathe a little easier
 

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Discussion Starter #25
I used to be the same way haha. First car had no a/c so I was used to driving around in 90-100 degree weather with the windows down. I really never felt comfortable with the windows up. The older I get, the less I drive with the windows down for some reason.
 

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I’m driving an hour to get alignment at team beefcake I will post final figure
Be aware as soon as I hit city and I floor it a few times
Goodbye mpg
Turbo eats fuel when you floor it
37516
37517
 

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Mine has received a steady diet of Costco 93 since purchased March '19 and is running a Cobb 93 tune. There's no evidence Costco's gas is inferior. Runs great and gets acceptable mileage (22.3 avg for 18 months). Thanks to Covid, the Costco here got down to $1.97. With their credit card and the store rebate, that made it about $1.86.
 

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Discussion Starter #31
Cobb OTS maps should be a pretty conservative, I'm sure you're fine with Costco 93 (y) I'd be hesitant to run it on a more aggressive custom tune. I finally set up the OAR PID on my Torque app, so I'm interested in the results from different stations. So far Shell 91 has been -0.99 at the lowest.

I've given up on my quest for better mpg for now. I've read multiple threads that said mpg well increase as the motor racks up a few more thousand miles, but I also tend to forget my "highway" drive isn't exactly a flat, steady speed drive. I lost 2-3mpg on my commute on my previous car when I moved to this house as well. I'm going to quit thinking about it and just drive :D
 

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Discussion Starter #33
Lol ok I'm waving the white flag, I'm not trying to fight anyone over it. Until I blow a motor running Costco gas, I don't have any proof that I shouldn't be running it, so I'll leave it alone :LOL: I've specifically been told by reputable tuners, shops, and experienced forum members in the boosted LS world to not run it (and my cousin that actually works at Costco doesn't even run Costco gas himself), so I'm going to heed their advice on my own personal boosted cars.
 

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I’m a guinea pig. I only use sams and Costco.
170k on my Scion, 26k mustang, 5k harley and 10k sportbikes

I’m cheap, and they have the best pricing of fuel around. 80c difference often from their 93 and shell etc per gallon
 

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Discussion Starter #35
I hear you man, I used to run it all the time in my V6 Accord. My mom will drive miles out of the way to get it lol, but it's not that big of a price difference here, so I tell her all the time it's nuts to drive out of the way and wait in line to save a couple bucks total haha. 80c difference makes it worth it :cool:
 

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Sams isn’t top tier. I had stuttering after fill ups and I was paranoid. But found out it’s prob my purge evap valve. I ordered a new one

after fill ups, car stutters for a moment
 

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Discussion Starter #38
Haha yeah I avoid Costco like the plague around here. Seems to be packed no matter what time it is.
 

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I own a 2018 base model, with 10R80 and 3.15 gears and routinely see at least 35 mpg, at 70 mph in ideal conditions. I've seen as high as 40.7 mpg, at 65 mph. These numbers are using the dash display. When I calculate the numbers myself, I typically see 1-1.5 mpg less. When I say ideal conditions, I mean 93 octane, dry, flat terrain, cruise control, daytime, moderate temps, no AC, windows up, light to moderate traffic, and only my 170 lbs in the car, with little to no extra weight.
Keep in mind, my car is the best version for mpg. It's the lightest, with the narrowest tires and has a .64 overdrive ratio and the 3.15 rear gears. Performance Pack cars add extra weight and inferior aerodynamics, in addition to the 3.55 gears.
There are so many things that can negatively impact mpg, such as driving style, mph, road conditions, temperature, AC and other electrical loads on the alternator, weight, tires, aerodynamics, and mechanical condition of the car.
 

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I can't remember where I read it but by adding the torsen rear diff the ecoboost PP looses mpg. Interestingly, it doesn't have any effect on the GT, go figure. On road trips I get about 28. When I got my MBRP Street Cat Back I actually got a bump on MPG but looks like my new Nittos aren't giving me anything back. Would it be cool to get the higher mpgs, sure but the car is just too much fun to drive that at the end of the day you don't care.
 
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