Soft Low Pitched Knocking After Oil Change. -
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post #1 of 3 Old 04-19-2017, 07:43 PM Thread Starter
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1990 XJ Cherokee 
Join Date: Jul 2015
Location: Brooks
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Exclamation Soft Low Pitched Knocking After Oil Change.

I usually use Pennzoil SAE 10w-30 for my 1990 Cherokee 4.0L, but this time I decided to use Chevron Supreme SAE 10w-30 because I had it laying around the shop.

Before the oil change i had 149,997 miles on it and used Pennzoil like I have in the past, and a Fram can of death "no problems luckily". exactly 1 year later (4/18/2017) I changed my oil at 153,000 miles with Chevron Supreme and a WIX filter. The next day i turn on my jeep and notice a low pitched knocking, I've searched and im not the only one to have this happen but i have not found any answers to why this would happen.

My best guesses are: Could the different oil type cause this? Does Chevron somehow use thinner 10w-30? Do I just need thicker oil like 15w-30 or even 10w-40? Could the Fram can of death have caused this? Did I develop this problem months ago but never noticed because the oil was old and thick?

Any suggestions and answers are helpful, ears open!

1990 Jeep Cherokee XJ with 153,010 miles and always maintenanced.

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post #2 of 3 Old 04-23-2017, 09:08 AM
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1988 MJ Comanche 
Join Date: May 2013
Location: bountiful
Posts: 83
Different brands of oil use different additives. As a general rule it is good to keep using the same oil for this reason. Where is the knock coming from? If it is from the pan that could be a rod knock. From the top it could be a lifter. They make a oil for high mileage motors. This has additives designed to swell old seals. Some engines have adjustable lifters and some don't.
I've always ran the 10-30 pensoil with no problems. I'd say that the problem may be additives.

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post #3 of 3 Old 04-23-2017, 11:39 AM
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2000 XJ Cherokee 
Join Date: Apr 2002
Location: out in the garage - Minneapolis
Posts: 25,789
Oil is oil, so changing brands of oil has no effect upon anything. My 1998 XJ has +264,000 miles and gets whatever brand of oil is in the 55 gallon drum at the oil change place, or is on sale at the nearest auto parts store. Old oil has had its additives used up and could possibly be considered thinner than new oil.

Naturally, you need to identify the source/cause of the noise, and then determine if it a usual/normal noise for a Jeep with the same age and mileage, or if it is a sign of a problem. Consider piston slap, lifter noise, or simple carbon build up as possible causes of the noise.

NO: 09-21-93
SUBJECT: Carbon Buildup On Top of Piston
DATE: Dec. 31, 1993

Symptoms vary from light ticking, to a ticking/hammering to a hammering/knocking noise as the carbon buildup increases with mileage and time. The noise is constant and more pronounced when the engine is cold. However, it may disappear when the engine warms up. The noise is most noticeable during idle, but will get louder as engine speed increases.

Carbon buildup is a relatively new condition that occurs during the combustion process and results from certain compounds in gasoline. These compounds form deposits on the top of the piston and cause contact between the cylinder head and the piston. The condition affects all gasoline engines and is industry wide. The brand of fuel and the type of detergents used by the gasoline supplier significantly contribute to the condition. Also, vehicles used in city traffic or light duty cycle operation are more prone to incurring the condition.

Make sure that all vehicle systems are operating as designed.
Using the Mopar Diagnostic System or the Scan Tool (DRB II) with appropriate diagnostic procedure manual, verify that all engine systems are functioning as designed. If Diagnostic Trouble Codes (DTC s) are present, record them on the repair order for future reference, and repair as necessary.

If all engine systems are functioning as designed, ask the customer about the fuel that is being used in the vehicle. If there is a question about the quality of the fuel, suggest that only fuels which are "warranted" by the gasoline company against the build up of deposits be used.

The use of Mopar Fuel Injector Cleaner has shown reasonable results in removing carbon buildup deposits. Add one bottle of Mopar Fuel Injector Cleaner (P/N 4318007) to a full tank of gas.


Mopar fuel injector cleaner is not intended for continuous use. Owners should be advised of the cause of the noise problem and a recommendation should be made to try other brands of gasoline.


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4.0 engine , cherokee , jeep , knocking sound , oil change

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