This 245DL non-turbo has 182k miles and runs well. As discussed previously, I wanted to get a baseline compression in case I ever have a problem, I know what's normal for my car.

Someone contacted me off list and suggested that I put oil into the spark plug holes and retest the compression.

Compression (in psi) before oil)
#1 166, #2 149, #3 168, #4 164; avg 162

I cleaned my fuel injectors and combustion chambe by introducing Greased Lightning Fuel Injection Cleaner into the intake manifold.

Compression was as follows:

#1 175 psi, #2 150 psi

then added motor oil into spark plug and tested #1 and #2:
#1 185, #2 170

What's this all mean?

What it means is you are getting too fussy. The acceptable variation for most engines is 10%, and for 1970's Fords it was factory quoted at 20%. When you drop a cylinder for a compression problem like a busted ring or a burned valve, you'll know it. Trust me. You won't even need the compression tester, just listening to the starter motor cranking will tell you. And then you pull the head off. Right now you have no worries at all. Drive it.

Ok when you added the lighting cleaner you took a little deposit off the valves, but as you can see from the compression results that it was not too much..You gained around 1 pound of pressure for making the valves seal a little better to the seats. When you added the oil you have now made a hydraulic cylinder... Just kidding but close.. you are now sealing the tiny scratches in the piston rings and cylinder that allow for some bypass gas when combustion takes place. Therefore you are creating higher compression as the gasses can not pass through the oil as easliy as it did without the added sealing of the oil..Making sense?? Its easy,, take a straw and blow through it, then blow through it with it dipped in oil, See the difference?? Same principal..Since you have added the lighting cleaner and the valves are now cleaner I would use the base line of those numbers without the addition of the oil..If you had used a constant pressure gauge to take the readings you would have found that after the oil is finally drained from the rings and piston that the numbers change to around the same as without having added the oil to begin with..By the way this is a good test to determine if you have bad valves or bad rings if you are losing compression..Pressure goes up with the addition of oil then the rings are bad, no change then you got bad valves..OK YOU GOT A LITTLE LEAKAGE OF THE RINGS IN NUMEBER TWO CYLINDER ...Max
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Max..1989 244 DL 5 Spd., Bilstein HD, Turbo Swaybars, Poly Bushings all round, Turbo Wheels, Black leather interior, Electric mirrors, LED dash and gauge lights.

Cylinder 1: 155 psi
Cylinder 2: 155 psi
Cylinder 3: 150 psi
Cylinder 4: 155 psi
avg: 154 psi