pvsprme

89 Limited, 4.0L, Auto, 4WD. 53K miles and using one quart/1000 miles. Compression test results:

1. 130
2. 170
3. 165
4. 155
5. 160
6. 170

Adding 30W to #1 brought compression up to 170 so it appears rings are going. Could it be a stuck oil ring? No visible smoke on operation or blow-by out the valve cover, rockers and valve train under cover are very clean. In addition to other tips, I did Cruiser 54's tip #25 and replaced air tubes and grommets to airbox and wherever else they go. This did help keep the filter element cleaner. I am starting to think it could be an oil ring sticking in #1, given the extremely low mileage, it was towed behind an RV for much of it's life. Doesn't seem right for the numbers to be that low in one cylinder only for this mileage. FSM specs compression at 120-150; Son-in Law's Snap-On compression tester instructions say 25% difference from high to low is normal, I'm in that range and it wouldn't be a concern if it weren't for the oil consumption. Maybe I'm spoiled by Japanese cars in my fleet, my Miata with 75K uses no oil in 3K OCI, Toyota Avalon with 225K uses 1/2 qt/3000 miles.
Been using Rotella 5W-40 T6 since acquiring this 7000 miles ago, Blackstone Lab report indicates all is well, all indices at acceptable levels.
Would going to a different viscosity (10W-30) reduce consumption? I've run the Rotella in other vehicles with excellent results.
Any point doing a leakdown test? I think not as it's pretty evident the oil problem is in the rings in #1.
Thinking about adding a quart of Marvel Mystery oil as it's down that much right now.
Thoughts & advice appreciated.

BlueRidgeMark

I like the MMM idea. Do the MMM top end treatment, too. Pull the spark plugs, toss a few ounces of MMM in each cylinder, let it soak overnight. In the morning, put some rags over the spark plug holes, turn the engine over a few turns to purge the MMM, and reinstall the spark plugs.

tjwalker

I like BlueRidgeMark's idea with Marvel Mystery Oil. In 43 years of wrenching and with an engineering background, I'm not much for additives but I will say that I have seen things loosen up with this stuff. Not frequently, but on occasion. Certainly worth a shot.

Question for you. It appears that this XJ wasn't run much recently. Did you buy it from the individual that towed it behind the RV? If so, how many miles have you put on it since you bought it? Just putting on some miles may be helpful here.

Try the MMO and just drive it. Then see where you are at.

Best of luck to you and be sure to keep us updated!

pvsprme

Yes, the previous owner towed it behind an RV, hence the low mileage for its age. I have put 7250 miles on it since purchasing last September, most of the miles being 50 mile trips. It does seem to be using less oil than when I acquired it. On purchase I replaced plugs (which look good after 7200 miles), rotor, cap & wires, refreshed and upgraded grounds and several more of Cruiser 54's tips, upgraded headlights with a Putco harness, relays and H4 lights, fluids changed. It had been converted to open cooling by PO. I have all receipts including window sticker.
It's very clean, no rust, leather & interior like new and everything works except power antenna; believe a PO put in aftermarket radio and may not have wired it in, It's always extended, shouldn't they retract when not in use?

BlueRidgeMark

That's my feeling. It's cheap, might work, and if it doesn't, you aren't out much at all.

cruiser54

Do the MMO. Keep us posted.

You could have cracked and dried up valve seals also. Not a huge job with only removing the valve cover.

are you seeing any smoke out the tailpipe?

pvsprme

Did the MMO this morning. No visible smoke ever. I will have someone follow me when I finish the MMO treatment. In previous vehicles when valve seals failed it was evident on start-ups. That's what's so frustrating about this, low miles, no leaks, no smoke.
BTW, can't thank you enough for the tips, most excellent. Working my way through them. The vehicle has spent most of it's time since I acquired it with my daughter, 80 miles away so I haven't been able to do all of them. Most grounds upgraded and refreshed (that blower one really makes a difference), Valve cover (tip # 25), Hella 55/80's and Putco harness & relays, headlight switch, fluids changed. Snow season is over in the Sierra where my daughter is so I'll have it till next winter; hoping to complete the others by then and upgrade the injectors.

cruiser54

Great plan!! blower ground really helps. and, you are less likely to melt the brown wire at the ignition switch...added bonus.

Is your air filter soaked in oil?

pvsprme

Just a trace visible, much less since I did your valve cover tip (#25?) and new air hoses.

cruiser54

But the consumption continues?

Does your motor oil smell like gasoline?

Nick-B

FYI, the XJ speedometers were mechanical cable driven thru 1990, so ALL miles register whether towed or driven. That engine has VERY low miles on it since it would be notably less than the 53K shown.

pvsprme

Consumption is about 1 qt/1000 miles. My sense of smell is poor, but no it doesn't; BL report doesn't indicate anything in oil to worry about.

cruiser54

Run it a coupla thousand miles.

BlueRidgeMark

Yep. Engines like to run, not sit.

pvsprme

UPDATE: Put about 3500 miles on it since the MMO treatment and consumption is 1 qt/2000 miles. I can live with that.