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Low muffled exhaust noise after oil change

I have a 2004 Subaru Impreza. I just took the car to Jiffly Lube to get a standard oil change (~70K miles). After the oil change, I drove it on city streets for about 10 miles, then as I was accelerating onto the highway, at a certain point when the accelerator was being pressed, the car made a very low, almost race-car type of muffled acceleration noise. It sounded like the noise that those supped-up street racer cars make. Definitely did not make this noise before the oil change.



As I drove home, I tested various acceleration scenarios and originally I thought the sound was related to the RPMs, but after further examination, I noticed that it actually didn’t have to do w/ a specific RPM, but rather now hard I was pressing the gas pedal. For instance, if I was in 3rd gear and running at 2K rpms, and gradually accelerated to 3K rpms, the noise wouldn’t come about. If at 2K rpms however, I floored the gas, the sound would occur.



Now, the only difference in this oil change is that I started using synthetic motor oil rather than the conventional that I had been using prior. The guy at Jiffy Lube didn’t think this would have any affect on the motor noise at all, and thinks it is somehow exhaust-related. It could very well be, but the timing of the oil change and the occurrence of this noise is too coincidental for me to think that Jiffy Lube didn’t have something to do w/ it (JL did say they’d be happy to look at it though).



Any thoughts? Could it have to do w/ switching over to synthetic? Could the oil pan or plug not be installed properly (I did check the dip stick and the oil level is normal)? Could JL have indavertently dinged the exhaust system while doing the oil change?



Thanks.

First: Keep away from the quick change places. We hear far too many horror stories about them. Some may be fine, but many pay the help little, demand fast changes and that results in a high percentage of errors. Too many live by selling you something you don’t need at inflated prices.

Find a good local mechanic and stick with them for your needs.

Don't go to the quick lube places, even for directions.

I doubt if it has anything to do with the oil that was used.  With a quick lube place you should consider yourself luck if they even put the oil in the right spot.  You should however check the oil level.  I don't believe there is any relation but can't hurt.  Note: too much oil is at least as bad as too little. 

I would tend to believe that it is more likely they bumped something in the exhaust system and that is the problem.  

Did they replace the air cleaner, that could be a source of a problem was well.

You should open the hood and see if anything obvious is amiss. Like, did they leave the oil cap off?

Tester

So I did check the standard items: Dip Stick reads normal, big yellow oil cap seems to be in place, no observed oil leak under the car after leaving it parked overnight, and they didn’t replace any filters (just had a major service at 65K at my local mechanic so most things needing replacement were replaced then).

Also, another piece of information that leads me to believe that the problem is exhaust-related: When I was driving to work this morning, I tried reproducing the sound, which occured as expected when I floored the gas pedal. However, I also noticed that when the noise was happening, that I picked up a faint vibration on the floor-board, perhaps some exhaust piping on the under-carriage?

I do try to avoid these places and take my car to a local subaru mechanic, but the convenience-factor is what takes me back every now and then…probably have learned my lesson.

In case anyone else is curious what happened here, I took my car to my local subaru mechanic and took him for a test drive. Once the noise occurred, without hesitation he said that it was the air filter. Jiffy Lube probably checked it to see if they could sell me something and didn’t replace it properly. When I got back to the shop, he took 5 minutes to properly adjust it and the noise was gone. He said he’s seen this many times before…simply awesome! Big props to my mechanic…if you have a subby and live in San Francisco, these guys have been awesome to me:
http://www.sfautoworks.com/

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While your mechanic may be awesome, the skill level of the kiddies working at Jiffy Lube is appalling. For your sake and that of your car, AVOID those joints like you would avoid the plague! If they don’t even know how to properly fasten the air cleaner housing, they certainly shouldn’t be working under the hood of your car.

As Mr. Meehan frequently (and appropriately) says–don’t go to a quick lube place–even for directions.

This quicky lube did an oil change but didn’t change the filter?

Did you tell them not to?

This just happened to me. I took my 2013 camry to walmart for an oil change. Upon driving home I noticed the engine sounded different upon acceleration. I googled it and came upon this thread and I’m glad I did. I checked my air filter and the cover was not reinstalled correctly. I fixed it and the sound was gone. Thank you.

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Same here… took my 2017 Malibu in for an oil change. By the time I got home I heard a rumbling growling noise. After reading your post the next morning I took the car back that evening. I explained to the tech what you described and he popped the hood and made the adjustments to the air filter. Magic! The noise was gone Thanks a million!!!