Lost 4 mpg. after pan mod

[howdee]

I have a 2011 eco manual with 26k. We bought primarily for use on the same hwy trip every two weeks. The best mpg was 39 by the guage, which I quickly found was always 3 mpg. higher than p$p actual. This is filling up just before and just after the interstate*.
After the pan mod, the #'s dropped to 35 guage and 32 p&p, 10 miles less than advertised.
My dealer says that the 2013 ecos are comming with the pan cut though I haven't seen proof and doubt Chevy could keep their claimed ratings having destroyed the car's aerodynamics.
All they need to do is put a couple rear facing louvers in the pan right below the heat shield so any oil can escape. Unlike the current remedy, this would preserve aerodynamics and mileage.

Anyone with a '13 Eco- how is your belly pan below the oil spout fixed?


* Tank always holds .7 gal more than dash says was used

 

[70AARCUDA]

Howdy, Howdee! A 4 MPG drop from almost 40 MPG is a 10% loss...that's pretty big for just an aerodynamic loss. I'd suspect tires, gasoline, and weather.

So, what air pressure are you running in the tires? Did your gas station recently switch over from 'summer' gasoline (lower Reid vapor pressure) to 'winter' gasoline? And, how much did the air temperature go down during that time? Temperature can be a DOUBLE whamee: (1) colder air means longer engine warm-up time, which reduces MPG; and colder air (2) causes loss of tire pressures because every 10ºF drop in air temperature results in a 1 psi loss of tire pressure.

Other people have commented that 2013 Cruzes actually are coming from the factory with "hand-cut" engine pan shields (ugh!), but supposedly a new shield is being designed.

Did you know that the exact SAME engine pan shield is used on 2013 Buick Veranos (Cruzes 'twin') but, ironically, THOSE shields have NOT been Safety Recalled!!! Seems the problem is directly related to the 1.8L and 1.4LT engines only.

 

[howdee]

Yes 10% drop seems unbelivable but true. Our trips are exactly the same and except for a slight allowance for lugage weight dif. , seasonal temps and blend adj.,our #'s have remained extreamly close. That is until the trip after the pan mod and ever sense.
My dealer went to far as to put my car up on a rack next to what i was told would be a'13 ECO which also had a cut shield. Then he played dumb when i pointed out the other one was an ls 1.8 and with lower mileage ratings than the ECO stick in large part due to it's lack of aero dynanic features such as the ecos grill louver which closes at high speed. That in itself should speak to the aero loss due to engine compartment resistance.
Lets face it, all the ls and lx's top out at 36 MPH,only slightly skinier tires, about 20 lb weight cut and the aero additions give the ECO 42 mpg.
Dont waste 6k on an eco when asimilarly equiped LS with atleast as good mileage.

 

[70AARCUDA]

FWIW, the ECO Cruze has different automatic and manual transmission gearing and final axle ratios than the LS and LT models:

...as well as different Engine Control Module (ECM) calibration via RPO: Y8X - FUEL ECONOMY - ENGINE IMPROVEMENT.