Compression Test Results - Help Me Come to Terms - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Svyx · 09-23-2014, 10:57 AM

So I have a 91 240SX, 240xxx-ish on the body, engine seems newer (Can't say for certain). The car would burn oil every now and then since I acquired it about a month ago (High revs, sitting for a long time at a stop). I recently changed the oil in it to a heavier weight to see if it helped, everything went smooth. Checked to make sure it was at the fill line, no leaks. Check.

Well, about a week later after changing the oil, it started burning it pretty bad, like at every stop and a lot of it. I did a compression test: Operating temperature, ran the fuel out, disconnected dist., unplugged spark plugs, WOT while cranking. I received 180-185 DRY across the board, which I understand is healthy compression. Proceeded to add a little oil, got anywhere from 190-195 WET across the board. A tolerance of 14 PSI is given between dry and wet IIRC. I then checked the oil level in my car, and now it seems like there's even MORE oil in it, like a quart over almost.

Are my rings that shot? Did oil magically appear? What's going on?

Kingtal0n · 09-23-2014, 11:02 AM

Oil can leak down the valve seals (common). It can also get past aged or broken rings.

Your compression looks good. more likely there is a problem with your dipstick. Check to see if your dipstick is pulling out of the engine slightly when you fill it, or that you are not on a serious incline when you fill/check it.

compression looks fine. you want even numbers, not necessarily high or low, because high or low can change depending on cranking RPM and accessibility to the atmosphere, and valve opening profile, etc...

Also if you accidentally filled the engine a quart over it may facilitate oil burning. It may also put excess pressure on oil seals.
make sure your PCV system is up to date, and serviced (new high quality parts) because it will help reduce oil consumption and relieve pressure on those oil seals.

Svyx · 09-23-2014, 11:06 AM

No incline. It was just weird how it ran with no smoke after the oil change, no overfill, and then started smoking bad with a bit of overfill. I'll go double check everything and get back. Thank you for the prompt reply.

09-23-2014, 10:57 AM	#1
Svyx Join Date: Sep 2014 Location: TN Age: 30 Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	Compression Test Results - Help Me Come to Terms So I have a 91 240SX, 240xxx-ish on the body, engine seems newer (Can't say for certain). The car would burn oil every now and then since I acquired it about a month ago (High revs, sitting for a long time at a stop). I recently changed the oil in it to a heavier weight to see if it helped, everything went smooth. Checked to make sure it was at the fill line, no leaks. Check. Well, about a week later after changing the oil, it started burning it pretty bad, like at every stop and a lot of it. I did a compression test: Operating temperature, ran the fuel out, disconnected dist., unplugged spark plugs, WOT while cranking. I received 180-185 DRY across the board, which I understand is healthy compression. Proceeded to add a little oil, got anywhere from 190-195 WET across the board. A tolerance of 14 PSI is given between dry and wet IIRC. I then checked the oil level in my car, and now it seems like there's even MORE oil in it, like a quart over almost. Are my rings that shot? Did oil magically appear? What's going on?

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09-23-2014, 11:02 AM	#2
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	Oil can leak down the valve seals (common). It can also get past aged or broken rings. Your compression looks good. more likely there is a problem with your dipstick. Check to see if your dipstick is pulling out of the engine slightly when you fill it, or that you are not on a serious incline when you fill/check it. compression looks fine. you want even numbers, not necessarily high or low, because high or low can change depending on cranking RPM and accessibility to the atmosphere, and valve opening profile, etc... Also if you accidentally filled the engine a quart over it may facilitate oil burning. It may also put excess pressure on oil seals. make sure your PCV system is up to date, and serviced (new high quality parts) because it will help reduce oil consumption and relieve pressure on those oil seals.

09-23-2014, 11:06 AM	#3
Svyx Join Date: Sep 2014 Location: TN Age: 30 Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	No incline. It was just weird how it ran with no smoke after the oil change, no overfill, and then started smoking bad with a bit of overfill. I'll go double check everything and get back. Thank you for the prompt reply.