Question regarding oil change

loscann48

loscann48

New member
Only had my jku for just over 2 months. Dealer did oil change prior to purchase with OEM filter. During that time I was getting 20.8 MPG's. Last weekend I changed my oil. Used a full synthetic of the same weight, and upgraded oil filter. Since oil change gas mileage has dropped to 19.7...Could this drop be because of oil and filter, or a coincidence? Suggestions, ideas, or comments welcome.
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JHP81 said:
i'm gonna go with coincidence.
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Agreed, most likely a coincidence. The 3.6L motor is fun and the longer you have it, the more likely you are to drive it harder. Well, at least that's been the case for me :crazyeyes: :D
 
wayoflife said:
Agreed, most likely a coincidence. The 3.6L motor is fun and the longer you have it, the more likely you are to drive it harder. Well, at least that's been the case for me :crazyeyes: :D
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While we are on the subject of oil, my Jeep is due for an oil change now and i'm not sure what kind they have in it (bought it used). But, can I buy a full synthetic of the recommended factory weight and it'll be fine? I remember hearing that if you run full synthetic, it had to have been since you got the vehicle new, that just switching to full wouldn't be good for the engine.
 
wayoflife said:
Agreed, most likely a coincidence. The 3.6L motor is fun and the longer you have it, the more likely you are to drive it harder. Well, at least that's been the case for me :crazyeyes: :D
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I have a 2010, so it's the 3.8 and there's nothing fun about that engine. Driving habits are the same. Guess we will see what happens over the next week or so.

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You're describing a 9/10 of a gallon difference in fuel mileage.

How are you calculating the fuel mileage? Onboard computer or manual calculation?
IMO the onboard computer is not that accurate. And if you use a manual calculation you need to make sure the tank is filled to the exact same level at each fill. The tires are at a consistent pressure. And the the speedo is calibrated to the size tire you're running.
Don't worry about small stuff. Go wheel and have fun. 😄
 
I noticed an increase in mileage when I went full synth. Made a road trip the other day and managed 21.8- 22 mpg's in my JKU.
 
I haven't had that great of gas mileage since I got my 2012. I knew it wouldn't though. I don't think the oil change will make that much of a difference at all. But I will pay more attention to it.
 
JK'AJUN said:
While we are on the subject of oil, my Jeep is due for an oil change now and i'm not sure what kind they have in it (bought it used). But, can I buy a full synthetic of the recommended factory weight and it'll be fine? I remember hearing that if you run full synthetic, it had to have been since you got the vehicle new, that just switching to full wouldn't be good for the engine.
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They say not to mix full and non syn. "because" the non syn will actually break down the full syn properties and it wont last/work as well. But as stated before you can switch at anytime id just be cautious mixing unless you're in a jam.
 
Gary Palms2Pines said:
You're describing a 9/10 of a gallon difference in fuel mileage.

How are you calculating the fuel mileage? Onboard computer or manual calculation?
IMO the onboard computer is not that accurate. And if you use a manual calculation you need to make sure the tank is filled to the exact same level at each fill. The tires are at a consistent pressure. And the the speedo is calibrated to the size tire you're running.
Don't worry about small stuff. Go wheel and have fun. 
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"Go wheel and have fun" Couldn't have said it better! :clap2:
 
Gary Palms2Pines said:
You're describing a 9/10 of a gallon difference in fuel mileage.

How are you calculating the fuel mileage? Onboard computer or manual calculation?
IMO the onboard computer is not that accurate. And if you use a manual calculation you need to make sure the tank is filled to the exact same level at each fill. The tires are at a consistent pressure. And the the speedo is calibrated to the size tire you're running.
Don't worry about small stuff. Go wheel and have fun. 😄
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I am looking at the on board computer and I don't have to worry about speedo calibration since I'm still bone stock. Not concerned with the actually MPG's as much as the sudden drop sudden 1.1 MPG drop. I mean its been pretty consistent until the last few days. Just making sure its not a sign of a bigger problem. I guess I will just keep an eye on it and see what happens.

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Since we're on the topic of oil change, I've heard that once you use synthetic oil it's not good for the engine to switch back to regular oil. Is there any truth to this?
 
Cheech said:
Since we're on the topic of oil change, I've heard that once you use synthetic oil it's not good for the engine to switch back to regular oil. Is there any truth to this?
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Has something to do with the seals. I did that in a previous rig went from conventional to blend and then full and back to conventional (was a shop that did it) they kept telling me nothing would happen and not to long after I was burning about 1 quart per 1,000 miles. Was it from the switching...I am no 100% positive but prior to that I never had issues.
I am curious if anyone else will chime in.
 
Cheech said:
Since we're on the topic of oil change, I've heard that once you use synthetic oil it's not good for the engine to switch back to regular oil. Is there any truth to this?
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On older vehicles like 1980's and older, going from conventional to synthetic can cause leak issues. Engines of today are made significantly more precise and will not have this problem. As far as going back to conventional after running synthetic goes, so long as your engine is in good shape and you are still using a good quality oil. Here is a link to Mobil 1 that says as much too:

http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Switching_Synthetic_Motor_Oil.aspx
 
Oil is always a subject of controvery in bench racing sessions. I use Red Line synthetic and they claim you can mix and match in any amount with any other oil. I dunno, 'cause I always carry extra just in case. Eddie's right, modern synthetics are so slippery they will lubricate everything and that includes the outside of your engine if it doesn't have tight tolerances and good gaskets. When I first used it in my Harley it was a sprinkling can. WTF? It took a complete new engine before it didn't mark its territory anymore. I'm betting however, my 2012 JKU would be very happy running Dino oil even here in the desert. It doesn't get any better mpg's on synthetic, it's just my choice to spend a little extra money on each oil change.:twocents:
 
I think I figured out the drop in gas mileage. Since first posting I have brought the MPG's back up to 20.7 twice (using the vehicles computer), only to have it drop back to low 19 fairly quickly. Well I did some looking into why and found a common denominator...my wife...she had always taken the jeep that day or the day before! Problem solved!
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loscann48 said:
I think I figured out the drop in gas mileage. Since first posting I have brought the MPG's back up to 20.7 twice (using the vehicles computer), only to have it drop back to low 19 fairly quickly. Well I did some looking into why and found a common denominator...my wife...she had always taken the jeep that day or the day before! Problem solved!
Sent from my ADR6400L using WAYALIFE mobile app
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The wind can cause a drop like that. It happens quite often with me, and my wife is not a problem... She scared of driving it :burst into laughter
 
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