19bonestock88's 07 "Malibu Eco" build

[Ecky]

In my car, A/C is worth about 25mpg when cruising at 50mpg - that is, I get 75mpg with it on, and 100mpg with it off. Your engine runs cooler because with the A/C on, there's a fan running full tilt all the time.

The (percent) impact on your car may be smaller, because it's probably about the same amount of load but your vehicle is much larger, but I'd expect better economy by opening up the block a little and not using the A/C to keep the engine cool.

[roosterk0031]

Not sure on the Malibu's but on my Cobalts, if air position control knob is just about to the floor position or anywhere farther towards the defrost it turns the A/C on. I'd guess A/C on is a 2-3 mpg hit for my XFE and Impala.

[19bonestock88]

I actually just did some testing, and you're right... With the APC knob any further than floor, it kicks on the A/C compressor, adding approx 10% load at idle... Coasting in neutral (engine running)at 40mph, it'll cut my MPG in half...

Since discovering that, I've been running with it off if at all possible...

[19bonestock88]

So, I've had a bit of a setback on my build, in the form of a broken spark plug that initiated a misfire... I noticed the miss on my way to work, last night of last work week... When I got home, I eventually removed plug 1 and noticed that the electrodes were gone, along with the center insulator... Feeling sick, I tried sucking it out with vacuum to no avail... Thinking it was already gone, I put in a different(but functional) plug and fired it up, and the misfire persisted, and eventually I heard a loud tapping that abruptly stopped... I removed the plug and found tap marks on it and the center insulator was broken(sliding up and down the center electrode)... Another functional plug was installed(only two of those left before needing to buy one), and re-fueled, and the miss finally went away... Maybe water in the fuel or something, but I've never heard of a 15k mile NGK plug failing...

Anyway, I did a compression check on 1 and 2 for a rough guess as to engine health... 2 had 190# and 1 had 140#, so I'm guessing something was damaged in the whole ordeal... Mileage is consistently down about 5% too... While in the same weekend, I switched to a 26 inch wiper blade, I doubt it was a 5%FE loss by itself...

[19bonestock88]

So, I guess this engine(and car) will live on... No signs of imminent death and running as it has always... On occasion, the idle is a little rough, but it's not out of the norm for a car nearly ten years old...

I have found a sticking caliper pin that'll need attention before long, and at least the rear rotors need replaced...

I'm also getting my best mileage, averaging over 40mpg indicated on most trips from home to the local towns...

[19bonestock88]

So, I've come to a point, where I have to ask, what next? I've got wheel skirts, rear wheel spats, an air dam, belly pan, and max pressured tires...

I still need to tuck the exhaust in order to build a diffuser, and really should redo my belly pan for smoothness(and ease of oil changes)...

Will making a higher flowing exhaust system help mileage?

Changing from panel filter to cone filter? I've got a K&N sitting around meant for a Cobalt SS... Higher flowing intake tube as well?

Not deleting the functional A/C, even though I don't use it...

Maybe higher voltage coils and wider plug gap?

[06Aveo43061]

impressive mileage for a 07 malibu.

I don't know how your stock airbox is in your malibu, but I did a box delete in my 06 aveo, and went with a cone filter attached to the stock intake hose. My stock airbox has an hole that takes in air near the passenger front wheel. We blocked that hole to prevent cold air from entering the new intake and to hopefully only allow warmer engine compartment air thru the new filter. After adjusting the ECU, I noticed about a 5% gain in my total miles on my tanks. Hope this helps

[19bonestock88]

I have been considering getting HPTuners software to tune my other car, and would also use it to tweak my Malibu for both performance and economy... My thought was lower idle(600 vs 800 RPM), leaner mixture across the board(though still richer than stoich at WOT), more timing advance across the board(except maybe idle), slightly earlier shift points(allowing 3rd and TC lock at 25bs 30, and allowing 4th and TC lock at 35 vs 40), and slightly more throttle allowed before downshift... This would allow me to lug the engine down to nearly 1000 RPM in some cases, and hold higher gears longer before kicking down...

[06Aveo43061]

That sounds like a good plan. Wish I could help point you in a better direction as far as reprogramming your factory ECU, but I know nothing about it.

[me and my metro]

Be aware that k&n air filters let more dirt through as well as more air.