Deal? 400for90+problems

Checked out a 90 pioneer today and ended up buying it, the aw4 (Im not used to autos) had good red clean fluid, 198k on it and the engine was 5, I repeat five quarts low. 500 or best offer. I was after an engine and ended up with another jeep for 400. compression was back to front: 115.105.130.130.130.105, It runs real good, oil pressure sender pegs out at 80+ not sure how to fix, have to test... transfer case mechanism needs the plastic pop in parts to get back together, its compleatly stock (I hate that stock feeling) and the upper steering joint to the pitman arm was shot, as well as front shocks, no radio, broken wires for cruise, tiny spare, rear main leaks like like crazy. Good things: new tires, but small, new exhaust, good interior, ok body, windows and locks/electric works 3x better than my beast. runs great for 198k. Now some would say it has way too many miles, but my 89 has 193k and runs like crap. I think it is a sensor still..., With the 89 I had for compression: pulling one plug at a time: back to front (first row) then with all plugs out(second row) and last with oil in the cylinder...(third)
95. 110. 115. 125. 90. 75.
115. 118. 115. 105. 90. 88.
120. 120. 125. 107. 105. 95. 1990 I just picked up dry cylinders:
115. 105. 130. 130. 130. 105
I think this thing has some life in it so I will use it to its capacity and meanwhile rebuild my 89=stroke. theres no point in putting a tired engine in place of another tired engine. I just couldn't pass up the price for a jeep that just needs general maintenance. what troubles me is that it sat for about a year and the guy selling it a guy take it for a test drive, they never checked the oil and it was five quarts low, with the sending unit malfunction they didn't know but still never checked the oil.

The computer screwed up on me but my questions were: should I run an auto in power or comfort mode(is power for towing and offroad? surely there is a gas milage difrence?) are there any fixes for a rear main besides replacing? I usually think of addatives as some sort of snake oil that never works but gives you cool side effects like runny nose, bleading colon, anal discharge, and loss of memory (im talking in reference to a jeep here...) the last time I changed a rear main it lasted about a year. I have also heard seal softeners are bad for a lot of things/ make things worse in the future... any truth to that? also, has anyone used "restore" and found actual positive results: like better compression that you tested? or with Lukas oil aditives?

Power vs. comfort mode: You'll probably notice very little difference, but it will depend on your driving style. In comfort mode you'll have to push it harder, which might actually end up with a little decrease in economy if you're in a hurry. Later models dropped the switch and default to power mode. that said, I always ran my 87 in comfort mode when not towing, and averaged about 23 mpg on road. I'd switch to power mode for towing and off road, though if you're going off road it may make little difference anyway. The difference is that it will shift later and a little more crisply in power mode.

I don't know of any substitute for rear main replacement that really works. Make sure it's really that, and not the oil filter adapter, oil pan, or valve cover, or all at once. Everything drips at around the same place. Fel Pro makes a special double-lipped seal for worn crankshafts that seems to hold up well. Check other things first, though, because if this is to be a temporary engine or a beater, you can have a bad crankshaft seal for a long time and not have to do anything about it as long as you keep an eye on oil level. In my experience the oil pan and filter adapter o-rings are more serious sources of real oil loss.

It's hard to imagine how anybody could get away with 5 quarts down! If it was run that way for any length of time without real damage, you're very lucky, or the previous owner never went around any corners fast!

I have an '88 Laredo with with the tow package that includes the switch. Basically it merely changes shift points to allow the engine to rev higher when in Power mode for a selected gear and a given load. It will also downshift a bit quicker too. As Matt suggests, it will depend on your driving style. I drive generally in Power all the time. I get about 15ish mpg city and about 22ish highway.

Also check the valve cover gasket. If it leaks at the rear, the oil can travel down the back of the engine and look like a rear main seal leak.

As for your oil pressure guage. Mine did that when i got it. Swapped out the sending unit. It was good for like 4 days then went right back. I never have chased the wires and such down, I just said screw it. If it blows i will throw another one in and then search the wires down..... Prolly just the sending unit tho.