OIL type change

[Caribbean ZJ]

Currently using Castrol syntec 5w 50. Wanna use chrysler recommended 10w 30. However round here, i can only get 10w 30 in coventional oil. will it be bad to switch from synthetic back to ordinary oil? 93 4.0 133,000 miles.

[hulkmn069]

from what i know conventional oil and synthetic oil don't get along when they are mixed in my opinion and that many miles i would advise against it unless you flush the motor really well.

[mx52nv]

or simply have someone on here ship you a few cases.

[Caribbean ZJ]

Flush? Wont draining the old oil out & a filter change be enough

[hulkmn069]

not really you need to do two oil changes to make sure all the synthetic is out cause the conv oil will not mix with the syn and bad things could happen just do a norm oil change just twice you may want to use two filters as well

[JDPascal]

I have never seen or heard any information that would indicate that there is a problem with mixing synthetic and dino type oils. Thats in 20 years of attending oil conferences and seminars.

Oil is oil and if they knew of an incompatiblility, they would warn you on the bottle.

A drain and fill with a filter change will be sufficient. You will not have any problems because of a change in oil.

JD

[dksob81]

how long have you been using Synthetic oil (how many miles ago did you start)?

[Caribbean ZJ]

3 yrs ago. Bout 20000 miles ago. I need to change my oil real soon.

[Sunbeam2]

What will happen if you have been using regular oil and you change to a synthetic oil?????

[Caribbean ZJ]

leaks.

[JDPascal]

While there is some logic to the assumption that switching to synthetic oil will cause leaks, that result is not born out in actual practice as much as you might expect.

This expectation is a carryover from the early days of synthetic oils when the composition of the oil was incompatable with the materials used in many seals. The result was that the seal material dried out and leaks happened. That was the main reason that manufacturers would not recommend synthetic oil for use in their engines 20 - 30 years ago.

JD

[dksob81]

Also to add on to what JD said - One very high mileage engines (what I think of high mileage would be 140k and up) Synthetic is not recommended because it will slip past worn piston rings and seals causing excessive burning (this is only on engines that have used regular oil the whole time)- but if you use synthetic I would just stick with the sythetic, unless it's causing problems. also not recommended for new engines (will harm the break-in period on brand new engine).

also it is not a bad idea to switch to synthetic under any circumstance, synthetic does help out with many many problems, it couldn't possibly make anything worse then what it is.

[JDPascal]

A friends mazda B2200 had a BAD smoking problem on startup due to the common head problem with valve guides and seals.

We changed it over TO synthetic oil and the problem smoke on startup has disappeared entirely. It didn't happen imeadiatly but over the last 6 months it has become a non issue at cold or warm start and oil consumption is not excessive in any way.

Individual circumstances can vary but synthetic oil flows better so the theory is that if there is a seal, it more of it will flow past the seal than thru it.

JD

[1BADGTO]

I've always used Mystic JT-8 oil and Fram or Wix filters. I have over 3/4 million miles using this oil and have tore down several engines and have always found them to be clean. I think as long as you do regular oil changes your engine will last.

My 95 4.0 Jeep has 270k on it and I have always used mystic 10w-40 every 4000 miles except for about 80k miles where I used Mobil 1 full syn 5w-30. I was driving like 4000 miles per month and was in a colder climate. I would go 8000 miles between changes. If I remember right I gained a MPG or two on the hiway using synthetic. Been using Mystic for the last 100k miles and loose about 1 quart every 2000 miles. As we speak I have the Jeep tore apart changing the rear main seal, oil pan gasket, timing cover gasket, crank seal and a new harmonic balancer to hopefully stop the leaks.

[Caribbean ZJ]

syntec it is. thanks.