Synthetic oil for a Jeep that sits?

These days it seems weird but I only drive my XJ once a week on a short trip to town. '94 2dr 4.0L XJ SE.

I need to do oil soon, and have always run conventional oil, but last year I did both the rear main seal and the filter adapter. So I suppose I do not have to worry about a synthetic oil cleaning gunk out of an old seal and causing a leak since I have a new seal. I am looking at whatever Advance has on special - sometimes I can get a Mobil 1 deal for around 25 bucks.

Since I am lucky if I get to do oil every 6 months, I would like to stretch it for a year. Mileage is not the issue, I put maybe 2 or 3k miles a year on it tops. My question is, if I let it sit will a synthetic last well? I have heard it can help with cold starts and I can use that because I live in VT where it gets below freezing 5 months out of the year.

I only hesitate because I do run an aftermarket Spectre filter which doesn't filter out all the dirt, and VT is very dirty. Dirty roads, dirt and salt on the paved roads in the winter, plenty of dust in the air. So maybe it is a moot point and the oil will get dirty just as fast?

I have been stretching things by doing conventional oil deals (either Catstrol or Valvoline) and running a PureONE filter. If I can spend a couple bucks more and get a few more months out of things, I am willing to give it a try. I do not have the cash to grab the high end synthetics at this point such as RP.

Any other thoughts on making this switch? I'm happy to leave the floor open on this topic since I haven't seen one in a bit from my searching.

I'm not sure what a Spectre filter is, but why wouldn't you use the best filter you can get (Wix as an example) which costs only a few dollars more than the cheapest ones? On second thought I assume a Spectre filter is an air filter?

What is a "high end" synthetic? RP? ASFAIK all synthetics are relatively expensive and considering your usage, again, why would you want something other than Rotella or equivalent?

Amsoil has the highest mileage/time rating. Their standard is 12 months, mileage ranges up to 25k (last I checked) Is really not much more, than most of the syn oil at the parts stores. As far as what parts stores offer, most have Rotella T6 (full syn) for a reasonable deal. Also, I always run a qt of MMO in my engine with oil/filter change.

To answer your questions about full syn oil. They will last longer than a dino oil. And, the myth of full syn. oil creating leaks is bogus. If there are leaks, the full syn will make it more noticable. This is due to the symmetrical molecule size.
In theory, you could run that oil for longer than 12-months as long as you change oil filter, and top off the lost amount when you do this. Really the only way to know your intervals better is to have an oil analysis done.

Yes, the Spectre filter is my air intake filter sorry that was confusing. My point is if my air intake is a bit dirty will it dirtyl the oil faster regardless if it is synthetic?

No complaints on jumping from conventional oil to straight synthetic? I hear many people suggest to transition with a synthetic blend but I don't see the point and wonder if this is just psychological and over-cautious.

I have been doing the MMO thing as well. 1 quart at every change. Should I keep it up with a synthetic?

Mobil 1 is on special sometimes so that is what I am thinking.

what is MMO?

Marvel Mystery Oil

I swap 1 quart of MMO in the change. I hadn't done this for a while but it was on sale last time so I got a couple quarts. Still have one actually. I have heard people going 2 quarts MMO 4 quarts conventional but I have never tried that. My hope is it keeps things clean.

My 4.0L has 168k miles on it and it still runs smooth and beautifully. I would like to keep it that way. I know down the road, many years from now when the rust monster finally wins, I could still sell the motor.

i switched from dino to T6 full syn at just under 100k miles on my 98. i valve cover gasket was leaking a tiny bit before and after about 5-6k of the synthetic it leaked more noticeably so i changed it. after that, it was still fairly leak free aside from the usual 4.0 rear main seal weepage.

Don't some of these high mileage syn blends have seal conditioners that swell gaskets? Perhaps that's a better option than full syn if you have some leaks?

Aren't you guys forgetting something? The 4.0 uses flat tappet hydraulic cams. They do not put the zinc additive packages in modern oil anymore, except specialty and race oils not available in local parts stores. You need to put in an engine oil additive in with the oil change. GM makes a good engine oil supplement (break in oil additive), Lucas also makes a break in oil supplement, and good old STP has a high zinc content (last time I checked), all of which are high in zinc additive package with the STP being the lowest (will work in a pinch) and the Lucas EOS being available in most parts stores.

I run full synthetic and 1 bottle of the Lucas EOS and 1 can of the STP for good measure.

^^^You apparently haven't looked at the makeup of "diesel" oils like Shell Rotella et al. These have high concentrations of zinc and you really do not need the additives with these oils.

There is a question as to whether or not our XJ 4.0s actually need the high zinc content but I will leave that for someone else to argue.

Check them again. Almost every one (everyone that I have checked) of them have cut down majorly on the additive packages in the last couple of years. I too used the diesel engine oils for that very purpose up until they changed their additive packages to almost nothing. That's when I went to full synthetic with the EOS. Look it up. They changed the formulations about 2 or 3 years ago.

And unless our 4.0's have a "magical" flat tappet cam and lifters, they need the additives. I have already wiped 1 cam in one of my vehicles for not using the additives.

Blah blah zddp blah blah. Plenty of idiots have 250k on their 4.0s using whatever shit oil was the cheapest.

Warlock1 said:

Check them again. Almost every one (everyone that I have checked) of them have cut down majorly on the additive packages in the last couple of years. I too used the diesel engine oils for that very purpose up until they changed their additive packages to almost nothing. That's when I went to full synthetic with the EOS. Look it up. They changed the formulations about 2 or 3 years ago.

And unless our 4.0's have a "magical" flat tappet cam and lifters, they need the additives. I have already wiped 1 cam in one of my vehicles for not using the additives.

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Guy on Cherokeeforum(salad) he's done a really well written and oil analyst on many oils, including the diesels(rotella,delo,delvac, etc..) and the T6 and the delo 400le are real good on the additive packages.

I'm just saying that I would rather be safe than sorry.

Here is a link that shows the drop in additives that I spoke of, look at page 5:

http://www.genosgarage.com/GenosGarageTechArticles/TDR76_LubeOil2012.pdf

You guys do what you want, but a $6 bottle of EOS is cheap insurance.

^^ I carefully read that multi-part thread recently, a masterful analysis of oils for our XJs.

Is salad making it all up? Is he deliberating misleading? Is he on drugs? I don't know but for the time being I will continue to use Rotella w/o expensive supplements.

And, as I understand it, all flat tappet cam setups are not the same but I will continue to use the oil with the zinc as long as the only thing it is presumably hurting is the cat.

synthetic oil at one year intervals sounds fine to me and would get oil circulating through the engine faster especially in your cold climate. from major retailers you can get shell rotella 5w-40 and online you can get amsoil or redline. amsoil amo 10w-40/ame 15w-40/hdd 5w-30/atm 10w-30 are all good choices. their amo, ame, and hdd are for pre-2007 diesels so they can keep the zddp at higher levels if that is important to you.

I don't think you're going to wipe a cam lobe on a 4.0 ... especially one on an XJ. If you do, it's from the first owner. The ZDDP helps if you have a new ,not work hardened cam ... The newest XJ is 13 years old - unlikely ZDDP is going to make much of a difference on a work hardened cam. At least, that's my understanding of it.

The biggest thing, as far as oil is concerned, for a vehicle that sits is getting it completely up to temperature (the oil, not the coolant - oil takes longer) when you do drive it.

Miller88 said:

I don't think you're going to wipe a cam lobe on a 4.0 ...

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It happens. Not so much as on a stock cam as an aftermarket cam. But it has happened to stock cams.

The ZDDP helps if you have a new ,not work hardened cam ...

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Nope. ZDDP helps the whole time. It provides a sacrificial layer to protect metal to metal sliding surfaces.

The biggest thing, as far as oil is concerned, for a vehicle that sits is getting it completely up to temperature (the oil, not the coolant - oil takes longer) when you do drive it.

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Very true, drive it for at least 30 minutes if it sits for a while or you do many short trips. While the coolant is up to temp the oil is usually sometime behind it. Also, do not do a lot of idling. The cam and lifters are mostly splash lubed and you need RPMs for that.

As far as synthetics with ZDDP Joe Gibbs, Brad Penn, Amsoil and others all produce oils with enough ZDDP.

Talyn, I guess the pertinent question is how much is enough ZDDP for our 4.0s?