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Q: My motor oil smells like gasoline, Why? ( Answered 5 out of 5 stars,   0 Comments )
Subject: My motor oil smells like gasoline, Why?
Category: Miscellaneous
Asked by: rogerpemberton-ga
List Price: $15.00
Posted: 29 Sep 2002 15:35 PDT
Expires: 29 Oct 2002 14:35 PST
Question ID: 70568
I have a 1998 Jeep Cherokee Sport with 68K miles on it.  I changed my
oil the other day and I noticed that it smells like gasoline.  I
checked it several times and it definitely has some gas in it.  I
would like to know why so that I can do something about it.  Also, if
you can find out what I can do to remedy the problem I would like to
have that information as well.  Thank you
Subject: Re: My motor oil smells like gasoline, Why?
Answered By: crabcakes-ga on 29 Sep 2002 16:56 PDT
Rated:5 out of 5 stars

As always, when it comes to cars, I check with my daughter who is a
mechanic. She immediately said “It sounds just like the fuel
regulator/diaphragm, but get a fuel pressure test at a reputable
mechanic’s shop. The reading will diagnose the problem ”. She said you
should expect to pay around $75 or better at a Jeep dealer. Because I
am not very fluent in automobile, I found the following resources to
back  up her “blind diagnosis”

From “Racing,“Gasoline can also find its way into the
lubricating oil because of internal leakage in the carburetor. The
gasoline leaks first into the cylinders, past the rings then into the

This article is about a Dodge(Chrysler)not Jeep(Chrysler), but it hits
the nail on the head! From, “The gasoline in the motor
oil may be caused by a ruptured diaphragm in your fuel pump.  Changing
the pump, oil and filter should fix the problem.”

More from 2CarPros, about a similar problem with a Chevy
Blazer:Question: 1995 Chevrolet Blazer with a 4.3 W vortec with CMFI.
The problem is that the engine is so rich at idle that it lopes and
stumbles. I replaced plugs (AC), wires (GM), cap, button, coil and
fuel filter and performed all the basic checks before I took it in for
diagnostics. The dealer said that the fuel injector was bad. I did not
believe them so I took it to someone else; they told me the same
thing. I replace the injector ($$$) this had no effect on the problem.
It is not logging any trouble codes in the computer. I have now
performed a compression test and all the cylinders are fairly even
between 158 & 170. I also took the valve covers off and measured the
lift at the rocker arms to see if there might be a cam lobe going down
nothing out of the ordinary there. I checked the fuel pressure it has
62 lbs at start and 54 lbs running. I have swapped the crank position
and the cam position sensors off my s-15, the idle air control and
have also swapped the O2 sensors. I have checked anti-knock sensors
8400 ohms, I have tested the throttle position sensor and the engine
coolant sensor all of which checkout with the book that I have. It has
17 inches of vacuum at idle so I don't think that it has a leak. Also
the timing seems high 22 degrees BTC. Nothing that I have done so far
has any effect on the problem. Any ideas? Answer: We suspect a faulty
fuel pressure regulator is causing your problem. The regulator may
have a ruptured diaphragm allowing the raw fuel to leak into the
intake manifold.

“a bad fuel pump diaphragm will allow fuel into the oil”

My mechanic says: “The first course of action would be the fuel
pressure test. Depending on the reading, you would start by changing
the fuel pressure regulator, and the fuel filter if it has more than
30,000 miles on it. Changing the air filter is a good idea as well.
Starting here will save some money, because if this fixes the problem,
there is no need, at this time, to continue. IF this does NOT fix the
problem, continue changing out the fuel pump and fuel filter. Next
check the “O” rings around the fuel injectors.” One or all of these
should fix the problem as these are almost always implicated as the
cause of gasoline in the motor oil.”


In case you are a do-it-yourself kind of guy, here are some Jeep
online part vendors:;$sessionid$TGHRASQAABBNKQSNDV1CFFCCJUOXKIV0

Here's hoping this helps with your Jeep. If not, please ask for an
answer clarification before rating.


Request for Answer Clarification by rogerpemberton-ga on 29 Sep 2002 21:11 PDT
Thanks for answering so quickly.  I would like some clarification on
one part of your answer.  Your mechanic suggests that changing the air
filter may also help.  I have a K&N air filter that I noticed is
getting filthy.  Could a lack of oxygen be a potential cause of this
problem?  Also, what happens if I find the problem and fix it but
don't change the oil?(I just changed it and I used full $$$$$ynthetic
for the first time!)

Thanks again,

Roger Pemberton

Clarification of Answer by crabcakes-ga on 29 Sep 2002 21:26 PDT
First, thank you for your kind rating of 5 stars!

I just called my daughter, and you may not like her answer! She said
if it were HER car, she would change the oil again after you make the
repairs.Gasoline may already have contaminated your new oil, and this
can be harmful. She DID say that a very dirty and clogged air filter
may have helped initiate the problem. (Not only do I adore my
daughter, but it is a wonderful thing to have my own personal
mechanic, and a good one at that!)

Good luck (I always wanted a Jeep!)
rogerpemberton-ga rated this answer:5 out of 5 stars
Answer could only have been better if responder had come to my house
to diagnose the problem and repair it.  Thanks

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