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Unread 05-17-2013, 12:30 AM   #1
perry32
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1998 XJ Cherokee 
 
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Engine Additives/Treatment for High Mileage

Hi All,

I just bought a 98 Jeep Cherokee LE - I6 4.0L with 135k miles and was wondering if there are any recommendations for an engine treatment to improve efficiency. Nothing noticeably wrong except poor gas mileage. Any product recommendations for
1) fuel system cleaner
2) engine oil additive/cleaner

Some products with good reviews I've heard are Sea Foam Motor Tune Up and Restore Engine Restorer and Lubricant. Would appreciate your advice!

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Unread 05-17-2013, 05:58 AM   #2
Newtons3
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Quote:
Originally Posted by perry32 View Post
Hi All,

I just bought a 98 Jeep Cherokee LE - I6 4.0L with 135k miles and was wondering if there are any recommendations for an engine treatment to improve efficiency. Nothing noticeably wrong except poor gas mileage. Any product recommendations for
1) fuel system cleaner
2) engine oil additive/cleaner

Some products with good reviews I've heard are Sea Foam Motor Tune Up and Restore Engine Restorer and Lubricant. Would appreciate your advice!
I dont believe in using any additives in the oil, with the exception of ZDDP during break-in. I run Berrymans FI cleaner. A lot of forum guys run Seafoam through the intake as an upper end cleaner. I have never used it. Berrymans and Seafoam are available at my local NAPA. As for Restore, I wouldnt use it to kill weeds.
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Unread 05-17-2013, 07:01 AM   #3
BIGBADWOLF
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Quote:
Originally Posted by perry32 View Post
Hi All,

I just bought a 98 Jeep Cherokee LE - I6 4.0L with 135k miles and was wondering if there are any recommendations for an engine treatment to improve efficiency. Nothing noticeably wrong except poor gas mileage. Any product recommendations for
1) fuel system cleaner
2) engine oil additive/cleaner
Best and safest way to clean engine is to use Rotella or Supertech diesel oil and change every 3k miles. After about 10 to 15k your engine will be cleaned of sludge and protected from wear with zinc. Using seafoam is too aggressive IMO and may plug up a lifter or cause a temporary blockage which could be catastrophic. Not so sure about fuel system,most of these additives are just different ratios of the same ingredients. I have used Marvel Mystery oil with good results.
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Unread 05-18-2013, 11:00 PM   #4
cruiser54
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Quote:
Originally Posted by BIGBADWOLF View Post
Best and safest way to clean engine is to use Rotella or Supertech diesel oil and change every 3k miles. After about 10 to 15k your engine will be cleaned of sludge and protected from wear with zinc. Using seafoam is too aggressive IMO and may plug up a lifter or cause a temporary blockage which could be catastrophic. Not so sure about fuel system,most of these additives are just different ratios of the same ingredients. I have used Marvel Mystery oil with good results.


This^^ and BG 44K in a full tank of gas.
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Unread 05-19-2013, 11:09 AM   #5
dmill89
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^All the above.

It would also be a good idea to pull the throttle body and clean it by hand (a can of throttle body cleaner, some q-tips, and rags). Nothing poured/sprayed on it will do as good of a job as pulling it and cleaning it will.

You can use seafoam, techron, BG, etc. in the gas (BG is probably the best but is harder to come by) though if your injectors are really dirty a professional cleaning (or replacement with reman units) may be necessary.

For the oil, as others have stated, just run a good quality synthetic and change often, additives can often do more harm than good.


By the way 135k mi is far from "high-mileage" for a 4.0L I6.
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Unread 05-21-2013, 12:07 AM   #6
perry32
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Originally Posted by dmill89 View Post
^All the above.

It would also be a good idea to pull the throttle body and clean it by hand (a can of throttle body cleaner, some q-tips, and rags). Nothing poured/sprayed on it will do as good of a job as pulling it and cleaning it will.

You can use seafoam, techron, BG, etc. in the gas (BG is probably the best but is harder to come by) though if your injectors are really dirty a professional cleaning (or replacement with reman units) may be necessary.

For the oil, as others have stated, just run a good quality synthetic and change often, additives can often do more harm than good.


By the way 135k mi is far from "high-mileage" for a 4.0L I6.
Ha. Well, the digital fuel economy reader says 13 mpg so either it needs a good cleaning or the reader is broken...

Thanks to everyone for the help
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Unread 05-21-2013, 10:55 AM   #7
tp72chev
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The #1 neglected part of every tune up is the o2 sensor. It is what regulates fuel mixture. If your lacking performance and fuel mileage, start with that. As far as additives go; seafoam is a great over the counter additive that you can add to the fuel and oil. The most common major engine failure for the 4.0l is varnished and sticking wrist pins causing the piston skirt to get beat up and eventually breaking. Products like Seafoam and Marvel Mystery Oil help to clean and protect against varnish build-up.
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Unread 05-26-2013, 03:39 PM   #8
JeepingJustin
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It's a jeep, mpg's are for the birds.

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Unread 05-26-2013, 04:15 PM   #9
CJ7-Tim
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Perform a complete tune-up with good quality brand name parts. Test the ignition coil. As suggested, clean the throttle body and use a good quality fuel injector cleaner in the gas tank every 4-6 months. I use whatever oil is on sale, no additives.

If you are experiencing low gas mpg's after your routine maintenance is completed, suspect either a cracked exhaust manifold, or failing O2 sensors. My 98 XJ Cherokee has 188,500+ miles and gets 19.2 mpg's on the highway. 13-16 city, or city/hwy combined would be normal. BTW you have to stay under 70 mph and accelerate like an old man.

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Unread 05-27-2013, 05:52 AM   #10
jeepdaddy2000
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First, you need to do do your fuel economy in real time. This means insuring the speedometer is accurate, counting gallons and resetting the trip odometer.
Don't be afraid to do a tune up. This includes plugs, wires, cap, rotor, air filter. Check your tire pressures. Stock tires can be run at the max allowed on the sidewall.
Slow down. High highway speeds will chew up efficiency, especially in sport utes.
You live in Fresno. Lots of time sitting in traffic with the AC on? driving habits and conditions will vary fuel mileage wildly. Take it in a trip. Open road in the 65MPH range should net you in the 20+ MPG area. We had a 95 GC that consistently ran 22MPG, and that included running the passes between Southern Oregon and Portland.
As stated above, 135K on any well maintained engine is well within it's service life.
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