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Old 04-09-2015, 04:32 PM
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Switching from Synthetic Oil to High Mileage Engine Oil

what about changing "from" Synthetic Oil to High Mileage Engine Oil
This fella at Jiffy Lube today talked us into changing, we had a 3 hour drive after the oil change. about 70 miles into the drive the engine started knocking really bad

I checked the oil right away, its still full

we made it home, but now I don't know what to do ? Make them fix it, or is that reasonable?

Any and all suggestions are welcome

1998 Jeep Grand Cherokee 253,000+ miles (4.0 6 Cylinder)

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  #2  
Old 04-12-2015, 02:34 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

It's always great to find someone to blame an get a free repair out if it. But honestly at 250,xxx miles it's about time to say she had a good run an use the block for a boat anchor an find a wrecking yard motor. If nothing's broke bad on the block you might be able to use it as a core for a reman motor.


95 ZJ.
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Old 04-12-2015, 05:22 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

not looking for hand outs here, I just need help figuring out whats wrong and get it fixed
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Old 04-12-2015, 06:00 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

There's a lot of hype about synthetics. And yes they are better. But "regular" oil wether a high mileage formula or not, is what was designed to be put in your motor. So switching back from synthetics probably didn't kill the motor. If it was a actual certified shop and they used factory approved oil, they probably won't be held responsible for the motor going out. No matter what was verbally agreed to or signed off on, if they put a fluid in that's been listed as not for use with your vehicle, they are totally liable for damage. Don't get your hopes up tho, at 250k on it, it's also totally reasonable to say it just plain worn out an time for a motor swap.


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Old 04-12-2015, 10:28 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

operative 31:
Yeah it may be time to swap the engine, we are second owners of this jeep, most of the miles on it are highway miles from us and previous owner, its just real strange since we've had it we have done all oil changes up until now and any other work, it has been very well taken care of and maintained. I guess its just a coincidence *sigh*

Thanks for all input from all
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Old 04-13-2015, 01:56 AM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

Those motors sell brand new for a lil under $1000. http://www.autopartsfair.com/jeep-us...9eb7&seq_num=1


95 ZJ.
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Old 04-15-2015, 11:48 AM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

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Originally Posted by operative 31 View Post
Since when is 100k+ miles brand new????
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Old 04-15-2015, 01:52 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

Jeep sells stroker 6's as crate engines, but they ain't no $1000.

I'd suggest the OP drop a bit of STP oil treatment into the crank case and see if that helps.
I wouldn't trust most Jiffy Lube techs to even put in the correct viscosity oil.

Even at 253K that straight 6 should not have gone from running well to making knocking noises just after an oil change... That mileage is getting up there, but on that engine some folks would just consider it well broken in.
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Old 04-15-2015, 02:23 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

Quote:
Originally Posted by operative 31 View Post
Those motors sell brand new for a lil under $1000. http://www.autopartsfair.com/jeep-us...9eb7&seq_num=1


95 ZJ.
In the link you gave and on the very top of the page of the link it says USED.

Anyhow it will be a tough fight to get any action from spiffy jiffy lube unless they leave out the drain plug or don't put any oil in to begin with. Make sure it has the proper oil level as too full or not enough will cause a problem. Is the high milage oil they put in also a synthetic? If it is synthetic then that really should have nothing to do with the engine knock. The rule I have always followed is once you go synthetic then keep it synthetic. My understanding is synthetic oils give a better metal to metal buffer or cushion that remains constant throughout the temperature range and life of the oil and also remains on the parts when the oil is not circulating. It has also been explained to me by oil company representatives that synthetic oil acts like a higher viscosity conventional oil in relation to thickness and weights. So in conversations it has been said that if you go back to conventional oil you should use a higher viscosity oil than the synthetic it replaces to maintain similar protection.
I personally would not trust the minimum wage high school technician that Jiffy Lube and similar oil change companys employ. I also think that the guy that recommended the change was wrong to do so. I hope they at least look into it for you.
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Old 07-16-2015, 06:23 AM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

thanks for the replys, been working on the 88' xj since my last post here, so now time to focus on this 98' zj ... I took a look at the oil and now the whole dipstick is milky

lstowell : it always had a slight knock (kinda high pitch) but like i said in my original post about 70 miles into the trip the knock got so loud could hear it over the music. When we got home the oil was still clear and full, changed the oil *iffy lube* put in back to synthetic and synthetic oil filter ... i had to move it so i started it and moved it about 500 ft then shut it down, had it towed to summer camping spot and now when i checked the oil its all milky so now i guess i have a blown head gasket also, some fella told us to start at the bottom of the engine, take the oil pan off, let it drain for a couple days and check there first ... any thoughts anyone?

leslie.thompson.7528: yeah shouldn't have let that guy talk me into different oil ~ they are not gonna help me
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Old 10-22-2015, 12:40 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

On high mileage engines do not change the type of oil. In fact I will not change brand.
On a previous high mileage vehicle (diesel powered pickup) I changed from regular oil to synthetic. I had engine failure about 2,000 miles later. The neighborhood mechanic I sold the truck to told me the oil filter was plugged along with some oil passageways. Mileage at time of failure was 613,2++. The truck was being used commercially over the road, 500 miles per day.
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Old 12-22-2015, 04:32 PM
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Re: Switching from Synthetic Oil to High Mileage Engine Oil

I would run 5w 40 delo full synthetic it's diesel oil good for high milage gasers because of zinc in it and its $19 at wally world, your 4.0 is realy like a tractor motor
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