From 38mpg to 45mpg on 07 Yaris hatchback by hypermiling and detailing exterior

[07yarisegg]

I just got back from a 450 mile trip going from San Francisco to Los Angeles. I wanted to implement all my different hypermiling techniques so I decided to wash, clay, and wax my car before my trip. Detailing it took about 5-6 hours since I'm guilty of washing my car maybe once every other year or less. That's gonna change now that I realize how much drag a dirty car produces.

The best mpg tank to date was a trip to Vegas using the exact same driving style and that only got me about 38mpg. For the longest time I couldn't figure out why my car was getting such poor mpg on the freeway, and it didn't matter that I did a full tune up including replacing the AFR/O2 sensor, spark plugs, filters, fluids, pcv valve, 45psi in tires, etc.

These hypermiling techniques included drafting behind large cargo trucks, never exceeding 65 mph (staying around 55mph), speeding up before a steep incline, engine off coasting (used very rarely).

After detailing my car, I decided to try a front upper grill block and used packaging tape on the seams between the hood and the front bumper. My license plate was already relocated to the lower grill and blocks a portion of it. I drove at night and arrived in the early morning and did so for each trip so my car wouldn't over heat, nor did I have to deal with traffic.

If I were to try another experiment on my next trip, I'd remove the passenger mirror as well as the wiper blades since I clayed and waxed all my windows.

So for those that haven't washed your cars in awhile and experience poor mpg on the freeway, try clay barring and waxing it. I'd like to find out if I'm the only one who experienced a large increase in fuel efficiency from doing so. Not only do you save gas money, you'd be saving your paint from failing prematurely, which will help your car retain it's value when resold.

Has anyone else experienced something similar after claying and waxing their cars? Does anyone have any other mods they'd recommend such as a warm air intake?

[Airstreamer67]

Congratulations on your great mileage increase!!

I will observe that IMHO, the significant increase cannot be attributed to your washing, claying and waxing. Although it can help a bit, it would not be so dramatic. There had to be something more going on to give you that kind of boost, such as a tailwind.

Trying to compare economy measures with just one trip, even a long one, can be misleading. Multiple trips under varying conditions over the long term would provide a more true evaluation of how economy techniques are working.

Keep up the good work!

[JockoT]

Washing and waxing doesn't make a difference. Something to do with Laminar Flow. And according to wind tunnel tests by Nascar teams, taping up panel joints have minimal effect. I think the majority of your improvements come from the adjustments to the nut behind the wheel. Your changes in driving technique have probably made the biggest difference.

[Jcp385]

Agreed. The stuff outside will have a negligible effect, if any. Fuel economy is far more heavily dictated by your driving than any modifications, etc.

I could probably get 15mpg or 50mpg in my car doing nothing but changing how I drive. I can't think of any mechanical or physical modification or change which would yield anything close to that spread.

[JockoT]

Originally Posted by Jcp385

I could probably get 15mpg or 50mpg in my car doing nothing but changing how I drive. I can't think of any mechanical or physical modification or change which would yield anything close to that spread.

No truer word said.