mudguards/flaps affecting mpg?

Re: mud guards killing MPG?

Arvin, what speeds do you typically drive? If your drop in fuel economy is in urban (or similar) driving, it is not from the mud guards.

On the other hand, for highway driving I can't be as certain. I thought I noticed a bit of a drop when I put mine on. But a "bit" of a drop can be caused by any number of things, including mechanical issues as mentioned by others here and weather conditions, wind especially.

The only way to tell for sure is a controlled test. Make a series of back and forth runs on a highway, with at least one round trip each with the guards in place and without, resetting the MFD after each (or using an add-on device like ScanGauge to figure trip MPG). The test route should be long enough to make it meaningful, say, 10 miles. Make the runs on the same day at the same temperature, no wind if possible, and with identical driving conditions; cruise control probably best assures the latter.

These days I don't worry too much about them because my highway driving is limited. For extended highway trips I can quickly remove them. I replaced the mud guards' factory screws with hex head screws and I keep a box end rachet to fit the screws in the trunk. This allows me to easily remove them without removing the rear wheel.

 

Re: mud guards killing MPG?

Side mirrors are a special case vis-a-vis aerodynamics. They are in a
particularly sensitive area where high pressure air is moving with a
slight diagonal movement across the windshield and then turning
around the A-pillar to move along the side of the vehicle. There is a
large probability that they cause turbulence. That said, I've seen it
reported that removal may gain ~2% FE, maybe 1 MPG for us.

The airflow down around the back of the wheels is anything but
smooth. Again, the airlfow is slightly diagonal outward. The wheel/tire
combination is churning up the air, and the wheel well openings add
more chaos. Mud guards are unlikely to have much aerodynamic
significance in this confused, jumbled up air mass.

So, I say put 'em on. The lower paint work will thank you. :rockon:

 

Re: mud guards killing MPG?

Arvind:

I see you wrote that

"I had my 60k service done and had the flaps put on with side moldings...."

I think the real issue is the 60k service. I think that something was done wrong with your 60k service, and that is what is affecting your FE.

Others have reported none or negligible impact from the mud flaps, so I would not worry about those.

If they adjusted your rear brakes you should look there. Also oil level, oil type (maybe they used 10w-30 instead of 5w-30), etc.

Best wishes,

Frank

 

Re: mud guards killing MPG?

I'm with yardman 49 as well -- they did something odd at the 60K service. I've had rear mudflaps on for 4 years and saw no difference in mileage, but a big difference in fender hygiene.