Hi all,

I bought a compression tester last week and I was very curious to test it out yesterday on my 2 bricks engines. I own 2 N/A's: a '95 and a '96. We bought them both second hand: 77K miles for the '95 and 59K for the '96. Now the '95 is at 127k and the '96 is at 90k. I always found the '95 less powerfull and less economical on fuel than my '96 since the beginning thinking that it was a different year engine.(both B5254S engines)
The compression is around 180 lbs average +/- 4lbs on all cylinders on the '96 and only ....... 125 lbs average +/- 2lbs on all cylinders on the '95. A friend of mine told me to drop a little bit of oil inside each cylinders on the '95 and do the same test again and the compression immediately jumped to 180 lbs..... He told me that the pistons and rings (or at least the rings) needs to be changed.

Question: Is it "normal" having now only 125 lbs of compression at 127K miles?

Thanks
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Jack

You definitely have some worn or stuck rings for the compression to increase 50% like you described. Looks like the engine wasn't maintained very well before you bought the car. If it's gummed up the treatment may help but don't expect anything to happen quickly. Additives are designed to clean gradually so that the oil passages don't get blocked it may take thousands of miles of driving to see a difference. Getting the rings replaced would be very expensive.

Hi there,

It's more likely that I have worn rings because the compression is even on ALL cylinders, I'll have to remove the head to know it properly. I'm thinking about it!

Thanks
--
Jack

Some of the professional Volvo mechanics that help out on this site have not had very kind things to say about ARCO gas and the crud it allows to build up in engines. Just a thought......

Just a side thought. If you have a "sludged up" engine...i.e., infrequent oil changes causing sludge to build up, you could have what is often called stuck rings. Basically, the groove in the piston that holds each of the rings can build up sludge and cause the rings to not move feely.

A solution that can help (short of taking them apart and cleaning them)is to run a couple oil change cycles using a fully synthetic oil like Mobil1 (has high detergents) or what I would more opt for since it is cheaper, run it with a quart of Marvel Mystery Oil (contains wintergreen oil and additives) which can really clean out any sludge or buildup nicely. Change the oil with whatever brand and subsitute a quart of MMO and run 3K miles or so and see what happens to your compression numbers.

Hi there,

I've been using Mobil 1 on both cars since the beginning, we bought the '95 in 2002. I'll try anyway the "Marvel Mystery Oil" at the next oil change and let you know

Thx for reply
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Jack

I would agree with 'db'. Unless the compression is uneven from cyl to cyl or the oil consumption is very high (much more than 1 quart/1000 miles), there is no need to do anything. I did not measure compression but on 3 Volvos, the oil usage started to go up around 170K, 150K and 120K. In our hands the first had quite a bit more suburb/highway driving than the later 2. On the later 2 we put on lots of city miles and short trips. The first 2 suffered sudden death at about 220K and 195K but were reliable in daily use until then. 3rd one is still being driven.

well, normal is relative to how the engine was driven to this point. I would expect that a well treated engine would have very similar compression ratings between 75K and 127K. Your readings indicate that the engine is losing some of its efficiency (or has lost some of it). However the fact that the readings for each cylinder are so close is really most important...as it shows there isn't a failure happening, just gradual wear. I have a Ford truck that the engine compression should be 180, but it is between 90 and 120 depending on which cylinder...it still runs fine and doesn't burn much oil (though power isn't that great any more and I run 15W-40). With proper engine treatment (oil changes, not beating on it) this engine could last another 127K and not have much compression loss at all. You may want to consider running a slightly higher viscosity oil going forward as it will help reduce oil burning and improve compression/efficiency. Unless the car is running poorly, can't pass emissions testing, or is consuming way to much oil, I wouldn't even consider a ring job at this point. And BTW, if your rings are worn, generally so are your valves, bearings, etc...