CaughtinmyGrill

I recently installed an AFE Proguard system and noticed an immediate drop in mileage. I went from 13.7 mpg in town down to 12.9 (all according to the overhead. I haven't refueled to be able to hand calculate my mileage.) I drove 150 miles with the AFE on and I just chalked it up to putting my foot into it.

Because I received the wrong housing, and need to ship the whole unit back, I put my stock air box back in yesterday. Immediately, my mileage jumped back up to 13.8 for the 20 all-city miles I have driven since. I purposefully drove as hard as I was with the AFE installed.

What would cause my computer calculated mileage to drop this significantly?

TXCatfish

My mileage went down even more than that without any change in driving habits. I also put the stock box back on and the mileage returned to what it was prior to the AFE.

Anyone?

vbert

I lost about 1 mpg on the computer and hand calculated when I installed the Scotty Ram Air III. When I put some weight in the bed to improve the empty ride I lost another 1 mpg. I get about 19 on the freeway now down from 21 mpg driving at 60 mph.

rossn2

Did you change the exhuast system? If you let more air in, you have to let it out too? Doesn't do any good to increase the air flow with a restrictive exhuast system...

PourinDiesel

Hmm...
A person at work reported similar results with an 03 Cummins after they installed a drop in AFE unit.

This one has me baffled.

CaughtinmyGrill

I've got a 04.5 600 with 4" exhaust, turbo back. I have a Edge Juice/Attitude that I am waiting to install. Once installed, I was going to monitor the EGT's to determine what mods I need in my exhaust system.

I don't think that the stock exhaust system would cause that drastic a change in mileage, but I could be wrong.

rossn2

Just by hanging a Brush Guard on the front of the truck, you tend to loose 1-2mpg?

I have an drop-in Amsoil oiled foam air filter and haven't noticed any difference either way. When I changed frt&read end, transmission, transfer case and engine out to synthetics, pick up 1-2mpg...so who knows?

Scotty

Here is my long shot guess about this...

More air needs more fuel and my guess is the ECM is seeing a leaner condition and is ramping up the fuel to compensate. [I am thinking Mass air flow sensor] I also feel that this as well as slightly different driving habits when adding an air intake or exhaust or whatever will hit the mileage a bit too. We all do like to listen, test and feel the difference an aftermarket product adds. Fuel quality can do this as well. When I use fuel in Canada I take a hit of at least 2 mpg compared to fuel in the USA. JMHO

Scotty

abc4yew

Guys, From all I've read about mileage ...apparently the cooler a diesel runs the worse the mileage. More cool air the cooler the charge, the cooler the exhaust, the cooler the engine. The best mileage is when the exhaust and coolant is hottest. If fuel is delivered at the same rate a hotter engine will have higher mileage. I used to have a link to a site that used a coolant that had a boiling point of 180 or 200 degrees C. that they used to boost the mileage or diesel engines. For every 20 degrees coolant temp there would be a 5% increase in mileage. Don't know all the facts and formulas but I'm sure some of the engine specialists out there do. KS