Cylinder Compression Test Performed - Ford Mustang Forum
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post #1 of 34 (permalink) Old 10-06-2011 Thread Starter
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Cylinder Compression Test Performed

Had a range of 160 - 170 psi on all cylinders. Should I be concerened with these numbers in general??? And should I be concerened with a 10 psi swing from high to low???

The test was performed as a result of me consuming oil at the rate of 1qt per 1k. After my first change and bringing back to the dealer after 1k miles (992 to be exact) I consumed 1/2 qt

Ford documented for me that 1qt per 1500 miles is the normal allowable range and my Vehicle is Operating Normally.


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post #2 of 34 (permalink) Old 10-06-2011
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10psi isnt bad from high to low, not sure what the actual compression numbers should be, but doesnt seem like anything to be overly concerned with. the car tuned at all?


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post #3 of 34 (permalink) Old 10-06-2011
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Quote:
Originally Posted by G-Mann View Post
Had a range of 160 - 170 psi on all cylinders. Should I be concerened with these numbers in general??? And should I be concerened with a 10 psi swing from high to low???

The test was performed as a result of me consuming oil at the rate of 1qt per 1k. After my first change and bringing back to the dealer after 1k miles (992 to be exact) I consumed 1/2 qt

Ford documented for me that 1qt per 1500 miles is the normal allowable range and my Vehicle is Operating Normally.
This kind of oil consumption is not normal. Ford wants you to keep putting oil in it, but I wouldn't even look at the dipstick until the Oil Life Monitor said it was time for an oil change. Blow that Sumbiatch up and have them put a new motor in there. The owners manual states that you are responsible for normal maintenance, not adding a quart of oil every 1k miles last time I checked.

I would be happy you are not driving a yota, their manual states 1 qt every 600 miles is normal. It is also important to remember that how you drive can have an effect on oil consumption. Very short ignition cycles, high RPM's, and high speeds. Also, remember that a new motor will consume extra oil during break in.


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post #4 of 34 (permalink) Old 10-06-2011 Thread Starter
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Thanks for the feedback

Stock tune on the car from day one until this test was wrapped up. After the test completed I did have them install the FRPP performance tune.

I dont think my initial consumption was normal at all but 1/2 qt per 1k miles is in line with other vehicles I've recently owned, G37s, 350z, FX45 so I'm no longer concerned.

I dont think it would be a good idea to not check your oil and let the engine blow and then have to have that battle with Ford. I have never come across anything in writting in the owners manual about actual consumption but it does say to check your oil ONCE A MONTH so it will leave them with an out if you dont check it at least once a month.

My consumption test Paper work says "Refer to warranty and policy Manual page 103 in version 1.8" for allowable consumption, I have not verified this info in my manual yet or in particular the version of the manual they list 1.8. Not sure my hard copies are version 1.8 that came with the car.

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post #5 of 34 (permalink) Old 10-06-2011
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so drive it 8000k miles in 1 month and call it a day.


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post #6 of 34 (permalink) Old 10-06-2011
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Ask them to do a leak down test and see how long the cylinder holds pressure.

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post #7 of 34 (permalink) Old 10-06-2011
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For my second oil change, I've hardly burned any oil. I'm 2900 into the batch.
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post #8 of 34 (permalink) Old 10-06-2011
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doing a lot of down shifting will cause more oil consumption as well, as a result of blow-by.

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post #9 of 34 (permalink) Old 10-07-2011
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Mine was 200-215 per cylinder. The car can actually perform a compression self test.

A leak down will tell you more about the condition of the engine but is a lot more labor intensive.

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post #10 of 34 (permalink) Old 10-07-2011 Thread Starter
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Quote:
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Mine was 200-215 per cylinder. The car can actually perform a compression self test.

A leak down will tell you more about the condition of the engine but is a lot more labor intensive.
wow that is a huge difference from my numbers. Was your test done stock or after your mods??? The higher the PSI the better I take it????

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How does the car perform its own compression test?
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160-170 seems a bit low but I have not run a coyote compression test. Did you do it with a gauge? If so did you run a dry test then a wet test? That will help identify if you have ruing issues. Squirt a little oil in each cylinder prior to the compression test. It will give you a more accurate reading of what the engine should make. If there is a huge difference then you have ring issues. The jump should not be more than 10%, but even with a tight engine you get a little jump. I would expect these motors to be around 190-200, maybe even more as the poster said above.

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How does the car perform its own compression test?
Mercedes also has this diagnostic feature. Basically the engine cranks with the fuel and spark deactivated. The crank sensor reads engine rpms similar to how misfires are detected with the engine running. If one cylinder is low on compression, the crank rpm will change slightly and can be precisely measured by the ECU.
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Mercedes also has this diagnostic feature. Basically the engine cranks with the fuel and spark deactivated. The crank sensor reads engine rpms similar to how misfires are detected with the engine running. If one cylinder is low on compression, the crank rpm will change slightly and can be precisely measured by the ECU.
That's pretty cool, does it give you numbers or is it looking for consistency across the cylinders. I have used diagnostic tools in the past that just looked for consistency. If one cylinder was down it would point it out, but if they were all down evenly it did you no good.

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That's pretty cool, does it give you numbers or is it looking for consistency across the cylinders. I have used diagnostic tools in the past that just looked for consistency. If one cylinder was down it would point it out, but if they were all down evenly it did you no good.
When the feature is so inclusive it can be very accurate. The readings show an acceptable threshold and if a cylinder reads low. While I haven't seen an engine with low compression in all cylinders in the test, that engine probably would not run or run well enough to even worry about doing that test. I would bet though that the test would be able to tell if all cylinders were low because the engine would crank over faster than normal due to the reduction in compression forces.

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