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Discussion Starter · #1 ·
New jeep wrangler with 15 thousand miles on it. My mileage has dropped to 16.2 from around 19.5 all highway miles. I was told I had a lot af carbon build up. I know nothing about this. Any one have any thoughs??

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That don't sound right. Gas mileage could be many things, heavier foot, head wind, winter gas, extra weight, the non aero dynamic roof rack you installed and so on. Carbon build up sounds bogus
 

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in my Audi 2.0t there is huge carbon build up issue but its direct injection. 3.8/3.6 isn't DI. not sure if carbon build up can crop up its ugly head. heres the carbon at 40k
 

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I'm curious, how was that conclusion made? Someone put a bore scope in somewhere? Winter mileage always seems to drop, some due to fuel blend, some due to warm up periods, maybe running in 4wd at times.
 

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Discussion Starter · #7 ·
Yeah I got an oli change and they did some kind of exhaust check and out of a 10 I was at 3 I don't know. But driving hadits have not changed but it has been colder and its the first winter I have had it. I have had the roof rack on the whole time I have had the jeep and it even stays the same mileage when I'm top.less. so it was at a jiffy lube not sure exactly what kind of test they ran but I will try to find out
 

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It's a rip off. . That test shows nothing at all and is just how quick lube places make money. After 20yrs in the auto parts and service bizz I've seen it all.
 

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Quick change oil service most times is a scam. That test is BS. They often have inexperienced people. Most times they'll over fill/underfill, strip your drain plug and otherwise try and get you to do bogus service like the "carbon build up". If you don't want to do it yourself you're better off at a local shop or even the dealer. Dealer oil changes are usually a fair price to even cheap because they use that to get you in the door before they try to up sell. A lot of factors influence the computer read out on fuel mileage. To be accurate you have to actually do the math.
 

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Discussion Starter · #10 ·
Yeah I thought it was crap. I'm sure it has to be the winter. Jeep drives amazing drove 1,500 miles in a few days with it. From the evaluation of 10,000 to sea level mileage did change a.little but that's to be expected. Thanks for your inputs they

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saved me money which can now go to more upgrades.
 

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New jeep wrangler with 15 thousand miles on it. My mileage has dropped to 16.2 from around 19.5 all highway miles. I was told I had a lot af carbon build up. I know nothing about this. Any one have any thoughs??

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First check your TB valve..if it's caked with carbon get yourself a good brand of TB cleaner and spray and clean your valve.

Next is get a can of Seafoam treatment and get your JKU into a WELL VENTILATED AREA. Next while the JKU is running pull your Brake Booster line and place hose into the can of seafoam and allow the engine to suck in the seafoam. The engine will chug and choke but try to keep it running till you have nearly sucked all the seafoam out of the can.

Once the can is empty the engine should stall...if the motor does not stall turn it off....let it stand for 15-20mins. After 20mins start it up again and enjoy the smoke show! After 5mins of idle take it for a good hard brisk drive to clean out the upper end of your motor. This will help clean any carbon build up in the upper portion of the engine.

I have been doing this every 2nd oil change without issue and it's amazing how quickly the TB valve carbons up! Also, I will throw in a can of Seafoam treatment into my tank when it's nearly empty (most concentrated) to clean out my fuel system. It does improve the MPG slightly.
 

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Discussion Starter · #12 ·
Great thanks for the advice. First jeep so I.might need some help finding and doing this but well just have to see. I will try to do.more research on this as well. Thanks again.
 

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Don't do it that way!! Just letting it suck it in well burn out the cat. Cleaning the valves that way should take about 15-20 minutes & using a short of IV drip tool helps. You should be seeing at least 3 quick drips with a quick pause after. And the engine should be at operating temperature. If you are seeing smoke while doing this, you're doing it wrong.

Doesn't matter what injection type you have since you have a egr that bring back the gas & the minor blow by the engine normally have. So carbon build up well happen. It's good to do about every 20k.

And don't judge your mpg off of the vehicle reading.not really accurate. Calculate it your self, if you haven't been.

And any cheap carb cleaner will work wonders as well. You don't have to spend big bucks to get a good one. Helps to have a scrub brush to. But a lint free rag would be ok.
 

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I add a bottle of Seafoam to one full tank at every 10,000 miles. My commute to work does not allow for heavy accelerations to keep things clean. What you will notice:
- Your Jeep will sound very coarse until the tank with Seafoam runs out
- It will run sluggish until the half of the next regular tank of gas, not really sure why. By the end of the second tank you will be good to go and ready to tell everyone about Seafoam.

$10 at any auto store or Walmart, absolutely worth it. These variable valve timing engines love to get dirty on the inside. I had a Caddy with GM's 3.6 VVT in it, Seafoam fixed it the same way. I have never done the direct into air hose method.

Check and change your air filter if needed, clean filter adds HP.
 

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BG products are good. I think better than sea foam.
 

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There was another thread about with higher grade gasoline getting a smoother engine run if there is carbon buildup. The reason allegedly is that carbon buildup takes space away from cylinder chamber therefore the compression ratio increases, which in return causes early combustion with regular gas (I think they call this knocking). Higher octane gas is harder to self ignite, that's why high compression ratio engines need it. At least this was my understanding, sort of adds up.
 

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Seafoam is bogus. The only reason it causes so much smoke is because it's petroleum based. Apparently people don't like to read directions either, because if you read them you'll see that you should only add a third of the can to the gas tank. If you truly want to learn about what works, go to Bobistheoilguy.com. The best performing fuel system cleaners are 1) Redline SI-1 and 2) Gumout fuel SYSTEM cleaner, NOT the fuel INJECTOR cleaner.
 

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I just did the sea foam treatment to my gas and into the brake booster vacuum line. If your going to do it, just follow the instructions on the can rather than taking second hand instructions from here. The can instructions are straightforward and easy. There is also a youtube video from the makers of sea foam showing you how to go about using it if you are so inclined. Running sea foam through my 3.8l caused a check engine light to come on the code was for a misfire on cylinder 6. Based off of the way the engine was running after letting the sea foam soak and starting it again that code didn't exactly surprise me. After driving it a bit and clearing the system out, it has been running well with a smooth idle and smooth engine acceleration through the rpm range. I didn't have any particular reason for trying sea foam other than the fact that I cleared 30000 miles and thought it might be good for preventative maintenance. As far as your situation goes with such low miles, I would say the winter gas blend theory and/or different load configurations are causing your drop in numbers. The drag created by kayaks or work caused by hauling around extra pounds of stuff in addition to the possible drop in air pressure in your tires (if you don't have nitrogen or didn't add some air in the colder temps) could easily cost you a couple mpgs.
 

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Seafoam is bogus. The only reason it causes so much smoke is because it's petroleum based. Apparently people don't like to read directions either, because if you read them you'll see that you should only add a third of the can to the gas tank. If you truly want to learn about what works, go to Bobistheoilguy.com. The best performing fuel system cleaners are 1) Redline SI-1 and 2) Gumout fuel SYSTEM cleaner, NOT the fuel INJECTOR cleaner.

Many including myself will dispute this. I don't use it on my low mileage Jeep but have used it on several 200K+ cars and it works great....a can through the brake booster hose works wonders...it will smooth up idling and help restore fuel economy.
 
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