Two questions regarding oil change - long

I've been following the list for a while, but this is my first set of questions. I bought my Jeep about three months ago; it's a 1991 Sport, and has 6 cylinder with a little over 158K miles. Overall, it's in good shape but it does have a manageable list of things that need to be addressed.

First, when I drained the oil tonight it had a strong gas odor. Could that be leaky injectors? This Jeep always seems to take a few extra rotations to crank, and now I'm thinking I might have an injector, or a few, that are leaking and therefore depriving the fuel system of it's needed pressure. If so, how would I check?

Second, since driving it home from the test-drive it's always had high oil pressure - like in the 70-80 range - no matter the speed or rpms. I saw a thread here recently that talked about the "acceptable" ranges of oil pressure and thought I might have a faulty sending unit. Well, since tonight's oil change, now I'm in the 30-40 range, even when I take it up over three grand, the gauge peaks around 45-50. Also, up until now the engine was typically noisy, but no valve chatter -- now I have some. The oil that came out of the pan was seriously dark and thick. Could it be the PO was running a heavy-grade oil, and now it's talking? On the plus side, it's a little more responsive.

For what it's worth, I used six qts. of Castrol 10W30 and a Purelator One filter. My 97 Grand has the same engine and I've used this oil/filter combo for over 100K miles with no noise or trouble.

Thanks in advance for any help or suggestions.

The oil pressure should drop at idle, and then go up to a higher pressure when running. If it always stays at the same reading, I'd suspect a faulty sender.

70 to 80 psi after warm-up is too high. Most run in the 50 to 55 psi range. My '88 MJ runs at close to 60 but I'm using Castrol synthetic 5W50 in that.

I think 10W30 is too light for your older engine. I ran 10W40 in my '88 from the first oil change up until I switched to synthetic at 175,000 miles. At 158K some valve clatter is normal and to be expected.

Thanks for the info. Is the oil so light that I should swap it out for 10W40? I'd rather spend a few bucks than do some uneccessary damage.

You said that you switched to synthetic. From what I've heard once you go that route you can't go back. Is that the case?

Thread Hyjack......

Is the Purelater and good filter? If not what filters do you guys run? When I put the new/old motor in (94 2.5L) what are the recomendations on good oils and filters?

I've run the Purelator One filters in my last three Jeeps (two 4.0s and one 2.5). All of them have run deep in the 100K mile mark with no oil based problems. My Jeep in question at the start of this thread came to me with a off brand filter but will spend the rest of it's life running the Purelators.

I've heard the Wix brands are good as well.

Doing a search on "oil filter" the other day, I found a pretty extensive thread with the pros and cons on the available brands.

My 98 has 182.000mi on it, since 5,000mi it has only had mobil1 in it. I also only use Mobil-1, K&N or Mopar. I would stick a mopar in for a baseline, filters can make a difference in oil pressure.

i use strictly Castrol GTX 10w40 and mopar filters.... used to run K&N all the time but lately just OEM filters....
mike

According to Castrol you can switch from conventional to synthetics any time you please. You can also switch back to conventional any time you please as well. Conventional and synthetics are fully compatable (at least Castrol is) with one another as well so you can top of synthetics with conventional and visa versa (although I'd prefer to keep one or the other running around my engine at a time)

I run only synthetics in all my Jeeps- 5w-50. I also change them a frequently as conventional oils. I've been running Fram filters in all my cars and Jeeps for years. Goes back to the days when I used to sell VW's and Porches. The mechanics at the dealership there swore by them and all the Porches left with Frams. Been thinking about switching to K&N lately, just haven't got around to it.

Perc. filters are kinda on the cheap side which makes me want to stay away from them... You tend to get what you pay for and an oil filter is pretty important.

Hi Sean! I only tink your seller made a bad think.

The very heavy and unusual hi presure can be performed to make appears the machine is in better condition than it is.

Here in Mexico is a very common way to sell the used and old cars.

Art Garcia

As far as whether it's wise or not to change out the new oil immediately, I doubt there will be any harm in running 10w-30, even though the pressure is a little lower. As long as it's within acceptable range, it should be fine. I have heard some arguments to the effect that as long as the pressure is adequate, it might even be better on the low side, because thinner oil flows faster, and thus will theoretically carry off more heat.

What I would do is run the thing as it is for a few hundred miles at least, and then change the oil without bothering with the filter. A crankcase full of thin oil gives you a good safe flush if you run it just long enough to pick up the crud in the engine, but not long enough to fill up with new crud.

thicker oil?

hmm.... '88/4.0/AW4/117k miles, I've been using 10w30 since I got it in January... think I should switch to something thicker next oil change?

Engine does have a few rattles I haven't identified yet; the most noticeable one seems to be coming from somewhere near the engine-transmission join, though it might be further forward, not sure.

Strong gas odor in engine oil can be: oil been in vehicle waaay too long, rings on one or more cylinder leaking; fuel delivery problem, etc. Even bad plugs not firing everytime.

Sounds more like delayed maintenance than anything. Just go thru it step by step and replace whatever needs it (and anything questionable) as to fluids, filters, hoses, etc. Consult owners manual and use scheduled maintenance items as a beginning.

As to filter, nothing better than BALDWIN B2-HPG for these motors (non-metric threads); low resistance to flow is more important than ultimate capture size.

More reading, if you like, although this Jeep of my wifes has but 60k on it now. Get that engine cleaned out, get the right filter and oil, and check the results:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000551

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000646

http://www.jeepsunlimited.com/forums/showthread.php?s=&threadid=411592

More info in first post:

http://www.jeepsunlimited.com/forums/showthread.php?s=&threadid=425976