Margie's68

The oil light came on in our olds so I did some PSI and compression testing on it; and now I am looking for some help. Before replacing the OP switch I tested the PSI and it was just a hair below 50lbs. Seeing that I had sufficent pressure I replaced the switch and the light is now out.

In researching the proper oil PSI, on the net, the highest number I found was 45PSI. Since the light is out, can I assume that 50 is ok, or is this too high?

Secondly, in doing the compression test I found a wide array of numbers on the left bank. The right bank had 3 cylinders at 130PSI and one at 125PSI, so I feel good about that. On the left bank however, they ranged from 115PSI to 127PSI, so I suspect bad rings as the front cylinder had oil in it. So my questions are; is 130 or so PSI the proper compression and am I looking at a top end rebuild for this thing? I suspect the rings seated in the motor because we were told it sat for well over 10 years.

This car was sold to us with only 20K miles on it and I suspect that is true. We bought it last year from some folks that got two Cutlass' at an estate sale and they sent us copies of the title they were given in 2007. The title that went with they car was dated 1980. The car was from New Jersey and there is no rust on it, which is why I also believe the mileage. I can hope anyway, can't I.

Carfax, and the other title searches, are no help on a car that old. Does anybody know how to prove that this car does indeed only have that many miles on it?

Thanks in advance Wayne

captjim

IMO, the best indicator of low mileage is the interior. If the seats are all worn out, it has been sat in a lot. Low mileage cars almost always have nice seats. Also, check the front end parts for tightness, age really does not affect them but mileage will.

Generally speaking, you want the compression to be within 10% of each other. 130 is OK, the one at 115 is a little low. It could be rings, but the valve seals could be bad after almost 40 years. Does the car smoke when it runs? Runs good or bad?

IMO, 50 psi cold is fine. At warm operating temp, the idle pressure will probably be lower, around 25-30. IIRC, the light will come on when it drops below 15 psi, but not at all certain about that.

rocketraider

The guidelines are generally all cylinders within 10 psi of each other, and no cylinder less than 80% of highest. 115/130= 88% so you're in good shape here. Those figures certainly don't justify internal work unless there's a valve-related miss or excessive oil consumption.

Oil pressure will depend on oil viscosity and temperature. 50 psi hot oil pressure is fine, excellent actually. You might also want to test cold oil pressure- as long as that's less than 80 psi you'll be fine. More than that can possibly stress oil filter materials.

I recommend use of diesel spec oil in older engines as they have better anti-scuff/anti-wear properties and better detergents. If you have a stuck oil ring in #1 cylinder, a combination of quality diesel oil and a quart of Rislone or Marvel Mystery Oil should clean the engine internals and unstick them after a few oil changes. The diesel oil will darken quickly; what it is doing is cleaning things up. Make sure you use a good quality oil filter such as WIX, NAPA, Baldwin, Hastings, Purolator or older AC.

If you're lucky enough to find inspection or other work receipts with car mileage, those are the best actual miles documentation I know of on an older car.

Margie's68

Thanks for the replies. As far as the seats, although the vinyl covers are a little roughed up at the joint where top and bottom meet, the overall condition is fine. The springs and cushions are great and they feel fine to sit in. IMO, once we get new covers on them the seats will feel nearly new.

As for front end parts, when we had the state inspection done a few months ago all it needed was ball joints. We put about 2k miles on it before it needed an inspection, and I assumed the rubbers dried out and leaked out the grease.

The engine does not smoke at all and it has not used any oil, other than what has leaked a bit from the pan gasket. (I need to replace pretty much all of the gaskets anyway because of dry rot.)

Thanks for the advice on the engine. I actually thought of trying the old Marvel Mystery to see if it would cure the oil blow by. Maybe if it can relieve a stuck ring or two, I might get some of that compression back to normal. As for the oil PSI, I hooked up the gage to a cold engine and ran it until the top radiator hose got hot. It started right at 50 PSi and went down only a lb or two when the engine was hot. From what you guys have said so far, I feel really good about my PSI in the motor.

Thanks again

Jokers69

this isn't a tell all, but look at the accelerator and brake pedal rubbers and the rug under the accelerator.. low mile cars shouldn't have a lot or wear on the pedals.