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Old 08-25-2017, 11:28 PM   #1
07liftback
 
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From 38mpg to 45mpg on 07 hatchback by hypermiling and detailing exterior

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?
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Old 08-26-2017, 03:51 AM   #2
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Good to know man thanks

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Old 08-26-2017, 03:27 PM   #3
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I find it unlikely that a 7mpg gain is possible from simply waxing the car. I'm sure a smooth surface will reduce drag but I suspect something else is responsible for your increased mpgs.
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Old 08-26-2017, 03:48 PM   #4
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The clear coat on my car is peeling so I'm not sure if that affects it at all

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Old 08-27-2017, 05:22 AM   #5
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Hypermiling

Quote:
Originally Posted by NYC-SE View Post
I find it unlikely that a 7mpg gain is possible from simply waxing the car. I'm sure a smooth surface will reduce drag but I suspect something else is responsible for your increased mpgs.
OP's opening post notes a number of aero mods done after the detailing and before the test run...then finishes with a contradictory question:" Has anyone else experienced something similar after claying and waxing their cars? "

So, needs to repeat test w/ a modified dirty car. And/or a detailed stock car.
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Old 08-27-2017, 08:34 AM   #6
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I did 45mpg (U.S. Gallons) with my 2009 Yaris just by driving it at 55mph for a non stop distance of 450 miles. Did nothing to it........just drove it steady.
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Old 08-27-2017, 07:12 PM   #7
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I personally don't think that waxing yiur car will get better mpg. I dont wash my car often and i still get great fuel mileage. Highway driving 6L/100km at best with 120km/h average speed. Clean or dirty its the same. Don't mean to shit on you OP! I'd say your increase in mileage is due to the hypermiling
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Old 08-28-2017, 09:06 AM   #8
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Iirc a few years ago there was a test done and it was found that a clean car will achieve better mpg. Lots of surface area paired with a smooth surface can do a lot. I don't think it alone is the reason for the op's very high increase in mileage but it has been shown to help and there is a definite plausible mechanism of action
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Old 08-28-2017, 11:14 AM   #9
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Quote:
Originally Posted by tmontague View Post
Iirc a few years ago there was a test done and it was found that a clean car will achieve better mpg. Lots of surface area paired with a smooth surface can do a lot. I don't think it alone is the reason for the op's very high increase in mileage but it has been shown to help and there is a definite plausible mechanism of action
That's a trip, but it makes sense.
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Old 08-28-2017, 09:42 PM   #10
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i heard once that the reason truck(semi) wash places are so popular is for the same reason- not just to look good. i guess if it's your rig is clean and you drive all day for a living it would probably make a difference($) in the long-run!

i know they don't go as far as clay barring, however. i just finished clay barring BOTH my vehicles and you can certainly feel a difference when you drag your finger across the paint!
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Old 08-29-2017, 12:23 PM   #11
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...i just finished clay barring BOTH my vehicles and you can certainly feel a difference when you drag your finger across the paint!
Big time. Just had it done to my better half's Honda and the difference was incredible. Her paint looked good, but felt like sandpaper. After the clay bar, it looked even more brilliant and felt like glass. It's really cool.
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Old 04-27-2018, 02:23 AM   #12
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Sorry to revive my old thread but I think part of the improvement could have been from drafting behind large trucks 70-80% of the time. On my way back from Los Angeles, I was only able to obtain 38mpg where I still drafted behind trucks 50% of the time and stayed under 60mph, usually 50-55mph. Not sure how everyone else in this forum is getting 40-60mpg easily on the freeway.
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Old 08-03-2018, 05:11 PM   #13
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Quote:
Originally Posted by 07liftback View Post
Sorry to revive my old thread but I think part of the improvement could have been from drafting behind large trucks 70-80% of the time. On my way back from Los Angeles, I was only able to obtain 38mpg where I still drafted behind trucks 50% of the time and stayed under 60mph, usually 50-55mph. Not sure how everyone else in this forum is getting 40-60mpg easily on the freeway.
Maybe... you're mostly going up hill?

I notice I get about 42 mpg going to my grandparents house, coming back I get about 47 mpg semi consistently. Back road going about 45 to 50 mph. Apparently grandparents house is at a higher elevation.

ALso, unless I'm within a car length distance with big trucks I don't notice much mpg increase. I have to be pretty close to them and cop pulled me over once and explained he wasn't too happy to see that. Legally you need to be within two car lengths he explained but didn't recommend doing that either.

Anyways I only got like 3 maybe 4 mpgs extra from that distance. I think I might get 1 or 2 mpgs at two ish car lengths behind big rigs. Which of course is better than nothing as it adds up. Going 70 on the highway gets me about 38 to 39 mpg within 100 miles. Same distance behind trucks got me 40 to 42 mpg. Of course it seems like the farther I go the better mpgs I get. went from georgia to michigan and got about 47 mpgs on the highway but it took a few hundred miles to max out mpgs. And of course on the way up and on the way back I got different mileage. but I believe 47 was the average for both trips.
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Old 08-03-2018, 09:20 PM   #14
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Buy skinnier tires.

I went from 175 to 195 and lost 5mpg (6L/100km to 6.8L/100km) doing 100% highway at 80mph
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Old 08-04-2018, 10:29 AM   #15
dogsridewith
 
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hypermiling

what was the spacing to trucks on the 47 mpg run?
Quote:
Originally Posted by Ilovemyyaris View Post
Maybe... you're mostly going up hill?

I notice I get about 42 mpg going to my grandparents house, coming back I get about 47 mpg semi consistently. Back road going about 45 to 50 mph. Apparently grandparents house is at a higher elevation.

ALso, unless I'm within a car length distance with big trucks I don't notice much mpg increase. I have to be pretty close to them and cop pulled me over once and explained he wasn't too happy to see that. Legally you need to be within two car lengths he explained but didn't recommend doing that either.

Anyways I only got like 3 maybe 4 mpgs extra from that distance. I think I might get 1 or 2 mpgs at two ish car lengths behind big rigs. Which of course is better than nothing as it adds up. Going 70 on the highway gets me about 38 to 39 mpg within 100 miles. Same distance behind trucks got me 40 to 42 mpg. Of course it seems like the farther I go the better mpgs I get. went from georgia to michigan and got about 47 mpgs on the highway but it took a few hundred miles to max out mpgs. And of course on the way up and on the way back I got different mileage. but I believe 47 was the average for both trips.
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