I know you may have been asked this question before but, what do you guy think about using synthetic oil in your Rubi? I used it in my Cherokee, which had the same engine, and had no problems that I am aware of. Is it, or will it be, as good with my Rubi? I use Castrol Edge motor oil.
Is synthetic oil ok to use?
- Thread starter Semper FI
- Start date
Once you go to synthetic oil you can not go back to conventional oil. I believe this is because the seals swell with synthetic and if it is replaced with conventional oil the seals will shrink and everything becomes very leaky.
I use synthetic in all my DDs with no problems. Come to think of it, never had any problems with conventional oil. I had extra synthetic in the garage when it was time to do an oil change and was lazy not wanting to go to the store for the conventional oil.
Bacon
I use synthetic in all my DDs with no problems. Come to think of it, never had any problems with conventional oil. I had extra synthetic in the garage when it was time to do an oil change and was lazy not wanting to go to the store for the conventional oil.
Bacon
Bounty__Hunter
Super Moderator
Excelent post Bounty, I used to worry alot about the brand of oil I used until I talked to a guy who tests oil that came in the factory where I work. He said, look on the back of the bottle and see if the designation (SF, SM or whatever) matches what your car requires, if it does...it is the good stuff. Since then I've been bargin hunting, I used Auto Zone brand oil for the last 60,000 in my '88 Cherokee. This engine already had over 100,000 on it when I switched. Worked great, never a complaint.
I use synthetic in my 2005 TJ without problems. I think as long as you change your oil regularly you'll be fine.
FYI - if you really get into the oil stuff, you can send a sample to Blackstone Labs to be analysed (it's actually pretty cheap). I did with mine, and they give plenty of information:
FYI - if you really get into the oil stuff, you can send a sample to Blackstone Labs to be analysed (it's actually pretty cheap). I did with mine, and they give plenty of information:
Blackstone Labs said:
Good post also Terry, I've seen 'em send samples out at work but never thought of sending 'em some Jeep oil. Just curious what brand filter do you use? I ask because it could have affected the results. Also they would be a good test bed to compair filters. Did they send you PPM graph or anything showing how much dirt was in your oil?
Thanks for all the answers. I was just wondering about synthetic oil because the Cherokee was the first vehicle I ever used it on. I never had a problem with the Cherokee. I use the Fram filter. I know a lot of you are going to say that, that is a bad oil filter to use. I was changing the oil, in what ever vehicle I had, at 3000 to 5000 miles and never had any problems. I have been using Catrol oil and Fram filters for close to 30 years and have not had one problem. I had one mechanic tear apart one of the 4.0's that I had been driving around on for well over 150,000 miles, and he told me there was nothing wrong with the engine. Not even any sludge in it at all.
I use Mobil1 filters as well. They do include more information, but most of it's over my head:
Good to see that oil has moly in it and zinc but I wouldn't know if it was a large portion or not. It'd be nice to have samples from other oils so you could compair 'em. I thought they took zinc out of the SM rated oils due to it being hard on cat converters as the engine got older and started to burn oil?
johnnstace
New member
This is a HUGE myth. The seals do not care. Besides 'conventional' oil is a blend anyway. The use of synthetic oil in today's engines is nothing but a marketing ploy by the manufactures and a waste of money. For older engines that run more towards the performance side (racing) there may be some benefit to the higher running temps the synthetic can handle.
john
Dragon5126
New member
never heard that one, never experienced it either. Since I do my own work I went to synthetic on all four of my vehicles, the 2006 TJ from the first oil change the 95 Taurus and 5.2 GC and 4.0 GC were converted over at that time there is 230K on the 98GC 165k on the 95 150k on the ford and 35K on the TJ... no noticeable difference in warmups, the only thing I have noticed is at the 5 K oil changes the oil is cleaner than it was with conventional at normal intervals. I am going to start having it tested just to see how long I can go especially on the 98 GC... I know the engine has at least 70 K left in it, it's not burning any oil, no leaks and has excellent compression. Just wish I could say the same for the damned PCM in it. the thing stopped sending ignition signals and needs to be replaced...
Jpwheeling2000
New member
Using Synthetic is the Way to go, using all Synthetic is ah-some, your Engine runs Cooler, you can see this in your engine's Temperature gage, any Synthetic well do, I buy mine at Costco, they sell Mobil, it gets kind of expensive when you do, so I just throw in one can of Synthetic. But if you choose use all Synthetic, your engine is going to run Cooler, its especially good for use FourWheelers because we run in Four-Low, you want your engine to run Cooler, try it out. If your running Regular Oil, here's what you should do, change your Oil to Synthetic, run for at least a couple days than change your Oil again, you engine needs to adjust, your all set, enjoy your new Cooler running Engine.
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Dragon5126
New member
No your engine does NOT need to adjust and IF you were religious with your changes there is no reason to flush your engine before changing over. BUT if you weren't then use conventional 10 or 5w30, MINUS one quart and add one quart of ATF fluid to make up the difference. the ATF fluid is extremely detergent and is what is used in heavy duty parts cleaning tanks. run it easy for about a quarter to a half of the normal change interval and then switch over. there is no need to waste expensive oil to do this. A flush like this will allow the full benefits of the extended mileage between changes right off if going to the higher grades of synthetic. AND if you beat your engine with conventional oil, put a quart of atf fluid in about 200 miles before ever oil change to prevent seizing your lifters up and prevent crud from building up in in the block and blocking bearing galleys
I am the original owner of a heavy ton 1990 Comanche.....255K miles now with the Renix 4.0L and automatic xmsn. I regularly pull a 4000 lb boat 250 miles to the gulf and back. I have used only Amsoil synth ever since the engine was broken in. I have changed the oil just once a year, regardless of mileage, for 24 years. I have no leaks, and never have to add oil between the yearly changes. Compression is still 150+/- in all cylinders, the motor is clean under the valve cover, and it gets 19 MPG avg (11 mpg @ 60 mph pulling the boat). Best vehicle I ever owned.
That sounds sweet. You should post some pictures.
