What weight oil does a 96 jeep cherokee use

Most likely 5W-30. The W is for winter. The numbers tell summer and winter. A quart of this oil will act like 5 weight (very thin) in the winter and 30 weight in the summer (thicker). Let's not go in to how that is done.
If you live up north, a 5W-20 would do well also. Down south 10W-30 is often used.

judging logically by what you mentioned I would check the oil pump first.

did you use correct oil weight could be sending unit. high miles?

Hello Debra Russ,
U may locate oil filter 4 2006 Jeep Grand Cherokee 2 way's.

1.) Open 2006 Jeep Grand Cherokee Glove Box, remove the 2006 Jeep Grand Cherokee owners Manual from glove box. Open owners manual to index page, locate oil filter page.

2.) Secure 2006 Jeep Grand Cherokee from moving fowards or backwards by blocking wheels in front and back which will NOT allow movement of said 2006 Jeep Grand Cherokee.

Using a small person of average build, average height, average weight, average intelligence, average physical appearance, move average said person with said average features of above near the 2006 Jeep Grand Cherokee, instruct said person to physically crawl under vehicle while laying on said person backside, (**** scraping on average dirty ground or average dirty filthy oil filled garage floor filled with oil filled kitty litter. Hand said average person an average shop light with an average wallmart brand soft white light bulb, light bulb will bo out very soon so move to next step ASAP. view engine while calling out all massive oil leaks INCLUDING a dirty oil caked oil filter.

Congradulations!
You found it when a black oil droplet drips from the oil filter into said average oil filled hair of said average person!
(insert smiles here)
FASTESTNASCAR

The rear wiper blade is 11 inches according to the attached.

http://www.partstrain.com/store/details/Jeep/Grand_Cherokee/Anco/Wiper_Blade/1996/AN3011.html?ptc=S1171391678W45d204bec356b&ptanjeepgrandcherokee19932007ancoan3011196wibl

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Mobil 1 5W-30 or 0W-30

THERE SHOULD BE AN OWNERS MANUAL IN THE GLOVE BOX,IT RECOMENDS THE GRADE OR VISCOSITY EXAMPLE 5W30, 10W30, USED IN ASSORDANCE WITH THE TEMPERATURES, CHART FOR SUMMER AND WINTER DRIVING.

Changing the oil grade shouldnt do that you may have a bad ignition rotor or cracked cap

At an Idle your 4.0 creates a vacuum between the throttle body and the intake valves. As you need more throttle less vacuum is created. The PCV ( positive crank case vent) works off this vacuum. At the back of the valve cover there is a vacuum line that goes to the intake manifold. This line can become clogged. An engine produces "blow by". If you were to take oil cap off you might see it at an idle. Check the air filter. there is a line from the valve cover that leads to the airbox. this is where the "blow by" goes when pcv line is clogged. Part 1 the problem...... part 2 the fix.

your parts store would call it an oil presure sending unit