Conventional oil VS Full synthetic

I have been running mobil 1 conventional oil in my 00 WJ V8 (oil change every 3,000 miles religiously)since it was new, now has around 110,000 on the clock. I switched awhile back to a mobil 1 full synthetic, and not long after it developed a light knock or tick on start up, that then goes away after a minute or less. I immediately switched it back to conventional, and have have changed the oil twice (tried different weights and filters) since the switch back. Outside of the annoying (man you must not take care of your vehicle) looks I get from people when it starts up, the thing has great oil pressure and runs smooth and strong. It is it possible that the synthetic loosened something up and blocked a passage or the pick up screen? I know the chevy guys have had issues with the vortecs doing this but I have not heard much of it from jeep.

I now live in fear of switching any of my other vehicles over to synthetic, even though I hear lots of great things, increase in MPG, better flow on cold starts, etc. Just curious what is run on here and opinions.

Synthetic is well worth the money and a great investment in any vehicle you intend to keep for a long period of time. The problem when switching to synthetic on a high mileage vehicle is you develop problems as you described. Another common occurance is for your gaskets to deteriorate. I don't know the science behind it but older / tired engines just don't seem like full synthetic. Someone here probably will chime in on that.

I started maintenance on my wife's 2000 TJ when we first met. That was around 50k mileage and I switched to full synthetic. Shortly thereafter the jeep developed a nasty leak from the oil pan gasket and RMS. On my 2001 XJ, it has had nothing but full synthetic 10w30 for it's entire life. Almost to 150k on the engine, no oil leaks, no oil covered drivetrain, and no oily engine block. Still haven't had to replace the RMS yet. :thumbsup: Engine runs and idles smooth and no ticking. I'm sold on full synthetics. :D

Almost forgot, I replace the oil and filter every 6-7k using full synthetic and not every 3-5. You might try a part synthetic or a high milage oil instead.

I have an 06 Trailblazer that I have been running synthetic in since about 15k miles and have had no problems at all, about 70k miles now. I change every 7500 miles.

I'm not sure if I would switch to synthetic on a vehicle that has a lot of miles on it. I have a couple jeeps and a chevy prizm that all were about 150k when I got them and I just keep dino oil in them and change them every 5k miles.

I bought a minivan not long ago that had dino oil changed every 3k miles since new. I almost switched to synthetic and actually would have but they were out of it so I put dino back in it. I think I'll just keep running dino in it every 3k miles as the previous owner did.

personally If i bought a vehicle new I would run synthetic in it after the break-in but I'm not sure if I would switch after it has a lot of miles on it.

I guess the next question is "what is a lot of miles? " :-)

I have run synthetic in my TJ 4.0 80,000 miles. The first few oil changers were with regular dino oil because it was a fresh rebuild. I have not had a drop of oil come from my motor. I have been using Castrol Syntec 10w-30 because it is readily available and meets AECA A1/A5. A3 is best but, the others are better than an oil not meeting the AECA specification. Good for the old school flat tappet cam in the 4.0.

Now I bought my MJ with 185K miles on the clock, naturally it has a leaking rear main and valve cover gasket. I have been running the same Castrol Syntec 10w-30 in my high mileage MJ as in my TJ. Replaced the valve cover gasket and it does not leak any more out of the RMS than when I bought it. I had the same result switching to synthetic in a 90 YJ with the 4.2 @ 100K miles on it.

Pilotblake, you could try a high mileage synthetic in the WJ. They are typically thicker and will stick to the valvetrain components better. This should keep good lube up there thus reducing/eliminating the tick. Maybe try finding some oil that is AECA A1/5 or A3 to see if it helps the grands V8. I am sure they are no designed just like the 4.0, or have their inherent issues, but might be worth a try the next couple of oil changes.

I have run synthetic in my TJ 4.0 80,000 miles. The first few oil changers were with regular dino oil because it was a fresh rebuild. I have not had a drop of oil come from my motor. I have been using Castrol Syntec 10w-30 because it is readily available and meets AECA A1/A5. A3 is best but, the others are better than an oil not meeting the AECA specification. Good for the old school flat tappet cam in the 4.0.

 

Now I bought my MJ with 185K miles on the clock, naturally it has a leaking rear main and valve cover gasket. I have been running the same Castrol Syntec 10w-30 in my high mileage MJ as in my TJ. Replaced the valve cover gasket and it does not leak any more out of the RMS than when I bought it. I had the same result switching to synthetic in a 90 YJ with the 4.2 @ 100K miles on it.

 

Pilotblake, you could try a high mileage synthetic in the WJ. They are typically thicker and will stick to the valvetrain components better. This should keep good lube up there thus reducing/eliminating the tick. Maybe try finding some oil that is AECA A1/5 or A3 to see if it helps the grands V8. I am sure they are no designed just like the 4.0, or have their inherent issues, but might be worth a try the next couple of oil changes.

Two questions...

Why do you specifically look for the European rating rather than an API rating??

Also why choose the API-SM rated oil that lacks the needed Zinc and Phosphorous for flat tappet motors? That being asked the Syntec is JUST a hair below what is considered the absolute minimum needed for flat tappet camshafts.

Most of the Hi-milage synthetics generally meet the API-SL rating rather than the SM rating. So they contain the higher levels of Zinc and Phosphorous that our flat tappet cams need for protection.

Why do you specifically look for the European rating rather than an API rating??

I am no expert, so I do not wish to argue this with an Amsoil guy ;) I based my selection after listening to people much smarter than myself explain oils. Seems every online Jeep forum has a few oil nuts. But in referance to your question the following is an expert of an automotive engineer's oil explanation:

SL rated oils. They may or may NOT have ZDDP. All they are required to have is better flat tappet antiwear protection. For perspective:

API SG/SJ aka ILSAC GF-1/GF-2 oils were allowed 30 units of cam/tappet wear AVERAGE before test failure (sequence IIIE for you oil nerds)

API SL oils aka ILSAC GF-3 oils were allowed only 20 units of average wear before test fail (sequence IIIF)

API SM oils aka ILSAC GF-4 allow 60 units wear before test fail (sequence IIIG)

 

It would APPEAR that by this information alone that the SL oils are the best. What about diesel oils? They’re not subjected to these tests at all! You don’t know how they’ll fare.

 

So, SL is the answer. UNLESS you dive deeper. Look at some EURO ratings.

 

ACEA is another term you’ll find on some oil labels. On it, you’ll see things like ACEA A1,B3, etc.

ACEA spec oils that meet A1,A2,A3,A5 allow only 15 units of cam/lifter average wear before test fail.

AND THEY HAVE NO ZDDP!

Also why choose the API-SM rated oil that lacks the needed Zinc and Phosphorous for flat tappet motors?

As mentioned above, the ZDDP found in most oils that are intended to protect the flat tappet cams can also harm the catalytic converters in our modern engines, assuming it burns some oil. It is my understanding that the API-SG/SJ oils were causing many flat tappet cam failures in the 80s because the engines were being reworked, running hotter, and smog was thrown in. API-SL oil came out and contained the ZDDP because it was a way to make a cheaper oil suitable for the newer engine demands. That is what is still around today for the most part.

That being asked the Syntec is JUST a hair below what is considered the absolute minimum needed for flat tappet camshafts.

I would love to learn from you as well. What makes the Castrol Syntec not up to the job for protecting the camshaft? Any information you have stating what specifications the Castrol fails to meet would help me out. As well as any documentation stating what oils you recomend that MEET or EXCEED certain specifications, none of that "for use where "insert specification" is recommended" that are suitable for our modern, flat tappet engines. Are the Jeep 4.0's the last of the flat tappets?

you got 110k on a 10 year old engine. bring it to the dealer and get a new car. I'm only kidding. i 5w30 synthetic is great, it is possible you switched to a 5w20, which is thinner and would weep through seals. I ran syntec blend in my old mud truck because i wanted it to still perform after 3 hours of on the floor mud slinging branch shakin action. i get better everything very impressed with it. put Lucas oil stabilizer in it. we run it at the gargae in the high mileage cars when the oil light comes on at idle, with the stabilizer it goes away. its crazy.

i use mobil one in a 2006 xb, 1985 635csi bmw, and a 1988 mj 4.o. no problems. i change the filter every 3000 miles and the oil every 6000 miles. different weights for different motors.

I just switched to Mobil 1 10w-40 High Mileage (available at wal-mart) at 104k miles on a 21 year old 4.0. I ran Shell Rotella-T for 1k miles before for ZDDP. My motor was pretty sludged up due to PO.

Noticed no difference except that my RMS drips oil alittle more now.

BTW Mobil 1 Syn is the only easily available TRUE synthetic, all the others Castrol(except 0w-20 German sourced), Quaker state, no name brand, etc. "synthetics" are actually highly refined dino juice... Amsoil, Royal Purple and Red line are TRUE Syn, but not as easily available.

http://www.bobistheoilguy.com

I am no expert, so I do not wish to argue this with an Amsoil guy ;) I based my selection after listening to people much smarter than myself explain oils. Seems every online Jeep forum has a few oil nuts. But in referance to your question the following is an expert of an automotive engineer's oil explanation:

I was mainly interested in the reasoning behind your specific interest in the ACEA ratings. Oils that meet them, or even advertise that they do are fairly rare in the US. Our politcal situation makes most oils unable to meet the equivalent ACEA rating.

And please question anything I might post that doesn't look right. If I had a nickel for everytime I posted something incorrect.. I would be retired some where with little government involvement and lots of sunshine.

SL rated oils. They may or may NOT have ZDDP.

ACEA is another term you’ll find on some oil labels. On it, you’ll see things like ACEA A1,B3, etc.

ACEA spec oils that meet A1,A2,A3,A5 allow only 15 units of cam/lifter average wear before test fail.

AND THEY HAVE NO ZDDP!

 

 

As mentioned above, the ZDDP found in most oils that are intended to protect the flat tappet cams can also harm the catalytic converters in our modern engines, assuming it burns some oil. It is my understanding that the API-SG/SJ oils were causing many flat tappet cam failures in the 80s because the engines were being reworked, running hotter, and smog was thrown in. API-SL oil came out and contained the ZDDP because it was a way to make a cheaper oil suitable for the newer engine demands. That is what is still around today for the most part.

I have to a take a bit of umbrage here with you and the good doctor....

ZDDP or Zinc dithiophosphates is the compound that is used by the oil companies to get Zinc and to a lesser extent Phosphorous into their oil blends. Two of the advantages of using ZDDP to get the Zinc is that ZDDP is easily soluble and fairly low cost. One of the disadvantages is that ZDDP will readily give up its Phosphorous when exposed to combustion temps.

When the EPA mandated a decrease in Phosphorous output from automotive sources the API created the SM specification. That particular specification only allows 800 parts per million of Phosphorous.. but there isn't any limit on Zinc. Zinc was never the issue, just the Phosphorous.

ACEA oils contain Zinc and Phosphorous, Here is a oil analysis from a ACEA rated oil...

http://www.bobistheoilguy.com/forums/ub ... ost1491262

You can see for yourself the Zinc and Phosphorous levels in it. So somehow they are getting in the oil. Does that mean its absolutely ZDDP? No, but the two important elements are in there.

I would love to learn from you as well. What makes the Castrol Syntec not up to the job for protecting the camshaft? Any information you have stating what specifications the Castrol fails to meet would help me out. As well as any documentation stating what oils you recomend that MEET or EXCEED certain specifications, none of that "for use where "insert specification" is recommended" that are suitable for our modern, flat tappet engines. Are the Jeep 4.0's the last of the flat tappets?

I am trying to find the related articles with an engine designer stating that the lowest level of Zinc should be 1000ppm in flat tappet camshaft motors. The VOA I found for Syntec showed the Zinc level at 966ppm.. but I cannot find it again at this moment. Probably as soon as I hit submit I will find it.

I run 15w40 Diesel oil in both my Jeeps....it seems to quiet the engines a bit and I havent had any negitive effects.

i run 15w-40 diesel oil in my 88 4.0 as well.i notice it takes some of the piston slap noise away and it burns alot less oil.