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JeepKid 01-22-2011 05:45 PM

Switching to RP and MPG's.
I have a question. LAst oil changed I switched to Royal Purple and used a K&N oil filter. Well when I changed my oil I reset the "oil change required" warning on the EVIC and it came on again about a week ago which is right on schedule since its been around 3k miles since my last change. Now I know when switching to synthetic you can go longer without changing the oil correct? Well I thought I would go atleast another thousand or so before changing the oil (too much?) )but I've noticed that when I go on without switching my oil my mpg's drop to around 12-13 city and it's doing it now.

I reset the oil warning but it seemingly had no effect on my mpgs. Now I am guessing this is because of the oil since it's happened every single time I've gone without changing my oil after the warning.

So my question is how did you guys get passed this ? Or is mine an isolated incident? Also, I am not basing this off my EVIC, I drove to Utah yesterday and spent nearly $40 in fuel coming and going where it would normally take me only $20 to come and go. Gas prices are still around the same as they've been for the past few weeks so I doubt it's that.

I feel like I'm missing something obvious lol Any help would be appreciated!

JeepKid 01-23-2011 09:29 PM

Re: Switching to RP and MPG's.

dmsfun 01-24-2011 03:06 PM

Re: Switching to RP and MPG's.
I used RP the last 2 oil changes and went 7500 miles between each with no change in mpg. in the Hemi. Something else is causing your mileage issue.

08Hemi 01-24-2011 03:36 PM

Re: Switching to RP and MPG's.
^X2...I don't think your oil could be causing that dramatic of an MPG loss after only 3K miles...and with the RP synthetic SHOULD be able to go 6K+ miles before your next change...hopefully some of the v6 guys will chime in

JeepKid 01-24-2011 10:42 PM

Re: Switching to RP and MPG's.
I figured the same but I swear EVERYTIME I've let my oil change warning go without an actual change it's always done this. Either way I'll be changing it tommorow so I'll see if it makes a difference.

TJXJWJ 01-25-2011 07:52 AM

Re: Switching to RP and MPG's.
I notice a jump in fuel economy in both my 4.7WJ and the wife's 3.7 WK for a tank or two after I change oil. I use the same stuff...RP and K&N filters. After a tank or two, the lofty MPG numbers settle back to normal. Despite what everyone says I change my oil between 3500 and 4000 miles because I'm mental. I've sent used oil samples in to an oil lab and it's still good. Like others have stated...I don't think it's your oil or interval creating the issue here.

You say your MPG's drop to 12-13 city. What are they before they drop?

JeepKid 01-25-2011 11:25 AM

Re: Switching to RP and MPG's.
They average 17 to 18 city.

TJXJWJ 01-25-2011 01:39 PM

Re: Switching to RP and MPG's.
Yeah, that's right about what our 3.7 gets. 17ish...but that's all the time.

It's something else. Are you up to date on all other service? Plugs, air filter, tire pressure, etc? Do you tend to take long trips after an oil change and then do a lot of city driving after that? A 3.7WK that is relatively stock shouldn't see 12-13mpg at all. Regardless of oil condition.

JeepKid 01-25-2011 06:30 PM

Re: Switching to RP and MPG's.
Well I just changed my oil but its freezing out so I haven't driven it at all. I changed my plugs about 15k miles ago and my air filter is in seemingly good condition. Tire pressure is good as well.

4.whoa 01-25-2011 07:18 PM

Re: Switching to RP and MPG's.
I don't think it could have a mileage effect, but you can change the oil service interval so the warning doesn't come on till later. :)

JeepKid 01-25-2011 08:40 PM

Re: Switching to RP and MPG's.
Just drove like 6 miles. For the past few days I couldn't get passed 13.1 . . . . I'm now sitting at 13.7??? I haven't changed my driving style either only difference was my oil change earlier.

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