[Cloud9...68]

I had an oil analysis done recently by Dyson Labs, and the analysis showed a high level of fuel dilution in my oil. This of course is compromising the oil's ability to lubricate properly, and if left unchecked, could significantly shorten the life of my engine. Oh, how I wish I had done an oil analysis when I first got the car five years ago.

The analyst, Terry Dyson, said this is a common problem in 944/968 engines, and looking through bobistheoilguy.com, it seems to be a not-uncommon problem in other engines as well. Terry told me the common causes of fuel dilution are things like worn plugs, plug wires, coil, distributor cap, rotor, clogged injectors, and a failing O2 sensor - basically anything that could compromize the combustion process. Other than the coil, I've replaced each of these items fairly recently, although the plugs, cap, and rotor, which were pretty worn, were done about 60% of the way through the latest oil change cycle, so maybe this was a contributing factor in my high fuel dilution reading.

My main question is, has anybody else done an oil analysis recently, particularly with Dyson? If so, did your fuel dilution reading come out high? Has anybody ever heard of this being a problem with our engines? My analysis also showed modest bearing wear (not bad enough to replace yet, though), and I could easily see prolonged fuel dilution in the oil being a contributing factor to the bearing wear our engines are known for. Terry also believes this is behind the relatively low compression readings I got in my last test (174-178 psi).

I've followed the regimen Terry recommended to deal with my dilution problem, and I'm hoping my new plugs, cap, and rotor will also help. I'll do another compression test after 3000 miles per Terry's recommendation, and will send another sample of my oil in for analysys to see if his recommendations have helped with my fuel dilution and bearing wear rate.

Finally, I would strongly urge anybody looking to maximize the life of their engine to contact Terry at www.dysonanalysis.com (no affiliation) and have an analysis done asap. Not only will it provide information that could extend the life of your engine, collecting a database of our engines' analysis results will provide invaluable, quantifiable insight as the specific problems to look out for as our engines age. There's so much folklore and misinformed conjecture surrounding this topic that having a pool of actual data would really be a great resource.

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[flash]

fuel in the oil is a result of unburnt fuel staying in the cylinder - it is a sign of one of three things:

1. gross issue with mixture - however you should also see black smoke, and have other issues

2. worn valves - this is very common - renewing the head will resolve this

3. worn rings - do a leakdown test to nail this down for sure

it is not a sign of bearings - low oil pressure, especially when hot, is the symptom that shows up there

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[Ryan]

I notice you have the racerX chip. I wonder if this adds to the richness problem as I have been hearing that our cars tend to run lean on the stock set-up.

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[flash]

i looked at the A/F charts when i did the chip shootout testing - the mix was fine on that chip - they got most of their power gain from timing adjustment

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[Cloud9...68]

<!--quoteo(post=73781:date=Jun 12 2009, 11:51 AM:name=flash)-->QUOTE (flash @ Jun 12 2009, 11:51 AM) <{POST_SNAPBACK}><!--quotec-->fuel in the oil is a result of unburnt fuel staying in the cylinder - it is a sign of one of three things:

1. gross issue with mixture - however you should also see black smoke, and have other issues

2. worn valves - this is very common - renewing the head will resolve this

3. worn rings - do a leakdown test to nail this down for sure

it is not a sign of bearings - low oil pressure, especially when hot, is the symptom that shows up there<!--QuoteEnd--><!--QuoteEEnd-->
I understand and agree. However, I found it interesting that Terry indicated that fuel dilution is a common problem he has seen with these engines, and appears to be so in some others as well. That's why I'm wondering if anybody else has ever done an analysis with Dyson labs, so I could get a side-by-side comparison between my engine's value (1.7%) and others'. Everthing else in the analysis (block, piston, and and valvetrain metals, coolant content, etc.) look great, so I'm wondering if my high fuel dilution may be relatively "normal" for this engine. I know that sounds strange - common sense dictates that no measureable amount of unburnt fuel in the oil should be considered normal. But you're right, a leakdown test would be a good idea. I'll do one when I do my next compression test.

And I didn't mean to imply that unburnt fuel staying in the cylinders is a sign of bearing wear - I meant the converse, that the effects of the diluted oil could be compromising the effectiveness of the oil, accelerating the wear of the bearings, which appear to be a bit of a weak link in these engines, anyway. But my bearing metals weren't terribly high, just higher than other things in the analysis.

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[xrad]

Another important question which Cloud9 alludes to is WHEN do you have your oil checked. On the same engine at 3,000, 5,000, or 10,000 miles on the oil, certainly there will be varying degrees of contamination.

Any lab can perform an analysis. The problem is , can they relate that to the engine in question (age, mileage, type of use, mods, type of oil)?

Optimally, I would think that you should use one test as a base reference, but other tests should be performed at regular intervals from a clean oil change and correlated with the engine in question.

Of course, if the fuel/oil ration is crazy bad, then you obviously have a problem.

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[Cloud9...68]

Yes, that's what I'm planning to do. I did another analysis with another lab at my previous oil change, but they didn't even pick up on the fuel dilution issue. So, in effect, this recent one with Dyson will serve as my baseline. I'm going to send him a sample at the next several changes to see what types of trends emerge as a result of corrective actions I've taken, as well as just from the normal aging of the engine.

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[flash]

i think maybe you are focusing too much on what somebody in the business of taking your money for an analysis is saying - do you think they would say everything was perfect and expect you to come back?

that isn't to say there isn't something going on, or that oil analysis can't be useful, but at your mileage, i could tell you what is likely without doing any tests at all

with a simple leakdown test, a look at your tailpipe, and a sniff of the dipstick (please hold the jokes to a minimum) i could tell you without an oil analysis, exactly what is going on with the engine

this seems to me like a case of looking for data to support what we already know:

older engines dump fuel into the oil due to ring and valve wear - duh

porsches do it more than most other engines - also duh

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[Cloud9...68]

<!--quoteo(post=73826:date=Jun 12 2009, 05:14 PM:name=flash)-->QUOTE (flash @ Jun 12 2009, 05:14 PM) <{POST_SNAPBACK}><!--quotec-->with a simple leakdown test, a look at your tailpipe, and a sniff of the dipstick (please hold the jokes to am minimum) i could tell you without an oil analysis, exactly what is going on with the engine<!--QuoteEnd--><!--QuoteEEnd-->
Yes, but the cost of driving out to LA, or that of a round trip ticket to get you out here, would exceed the cost of the oil analysis [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

I hear what you're saying, and I will do a leakdown test. Not to get too far off the subject, but, while I've never had a leakdown done, I think I understand how it works (bring pistons one-by-one to TDC, and pressurize the cylinders through the spark plug hole with some sort of inert gas - N2 I would imagine, and measure the rate of pressure drop on an attached gauge - am I close?) The thing I've never understood is, how does this test distinguish leaky valves from leaky rings any better than a compression test?

The thing that puzzles me is that my engine doesn't display any other symptoms - no smoke, ever, passes emission every year with flying colors, very little oil consumption, etc. That's why I'm holding out hope that my dilution is caused by something other than valve or ring wear. On bobisteoilguy.com, people have reported fuel dilution from ignition issues, and also from things as obscure as a fautly thermostat. So, we'll see. I'm not tracking the car these days, so I'm not in any rush to do any major work to the engine, even if the leakdown test were to indicate that expensive things are getting leaky.

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[flash]

simple air from the compressor - very easy thing to do - you can buy the kit for $40 from harbor freight

lol - i understand the wishful thinking, but it's pretty rare to have something else going on, and they would show other symptoms, where normal wear generally won't - your numbers are very normal for the age, and it is normal to have some fuel in the oil at that age

best of luck

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[xrad]

But if you are not going to rebuild the head and block, and just do the peripheral fuel control devices, it really does not matter what the lab or the dipstick 'says to you'.....

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[flash]

lol - unfortunate reality of age - cars or people - you can go to the doctor every month and they will still tell you the same kind of thing: your reflexes are slow, your vision is failing, you aren't as strong, yada yada - they can find causes all day, but the reality is that unless you get a new body, it is what it is - no amount of analysis and testing will change it

fortunately getting a new engine is a lot easier than a new body - it's a pretty good chance that it only really needs head work right now too

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[S_Cal968]

Typically when performing a leak down test I'll listen closely to the intake, exhaust and oil filler - this helps determine whether a valve and/or rings are leaking.

Regarding fuel dilution; I would ask Mr. Specialist if this is common with all high compression, high revving 4-cyl engines[?] Also, does the comparative baseline data include engines with low miles/hours?

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[Cloud9...68]

Thanks for all the inputs, but I still don't understand how a leakdown test will tell me whether the valves or rings are responsible for my somewhat low compression numbers. I agree that at 107K miles, on an engine which, according to the records, got an oil change an average of every 2500 miles before I bought it, valves seem to be the more likely (although the fuel dilution is a nasty clue pointing more to rings [img]style_emoticons/<#EMO_DIR#>/mad.gif[/img] ), and fortunately less expensive, culprit, but how will a leakdown test shed light on which it is? Thanks.

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[firefish]

<!--quoteo(post=73892:date=Jun 14 2009, 01:57 AM:name=Cloud9...68)-->QUOTE (Cloud9...68 @ Jun 14 2009, 01:57 AM) <{POST_SNAPBACK}><!--quotec-->Thanks for all the inputs, but I still don't understand how a leakdown test will tell me whether the valves or rings are responsible for my somewhat low compression numbers. I agree that at 107K miles, on an engine which, according to the records, got an oil change an average of every 2500 miles before I bought it, valves seem to be the more likely (although the fuel dilution is a nasty clue pointing more to rings [img]style_emoticons/<#EMO_DIR#>/mad.gif[/img] ), and fortunately less expensive, culprit, but how will a leakdown test shed light on which it is? Thanks.<!--QuoteEnd--><!--QuoteEEnd-->


If you pressurize it, depending on where you get the "hzzzzz", you can tell where/what the problem is. With all valves closed (for the tested can) and you get an intake hzzz the valves aren't sealing. Noise in the exhaust means dito for the exhaust valves. Hzzz from the oil filler leans towards blow by (bad rings) but could also be worn valve guides (lift the cam cover and check).

How did you do your compression test? By taking out the plugs and using a manometer (right word?)? This method doesn't really tell you how high your compression is. However it is usefull in that you can compare all four cylinders to see if the numbers are the same (or about the same anyway). I did this to my 340 in the cuda and all eight was between 9,5 and 10. It doesn't matter what the numeric value is, the key is in that they are very close (at least for a high mileage V8).

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[xrad]

a little smokey on startup? my guess is valve guides and seals...and while the head is off, you can check the cylinder walls

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[Cloud9...68]

<!--quoteo(post=73902:date=Jun 14 2009, 08:27 AM:name=xrad)-->QUOTE (xrad @ Jun 14 2009, 08:27 AM) <{POST_SNAPBACK}><!--quotec-->a little smokey on startup? my guess is valve guides and seals...and while the head is off, you can check the cylinder walls<!--QuoteEnd--><!--QuoteEEnd-->
No, not a bit. Not a whiff of smoke, not on start-up, not at WOT, not ever (and I've had people drive behind me to confirm). Also, my oil consumption is quite low. The primary reason I did the oil analysis was to get a read on the bearing metals, as I'd been agonizing as to whether to tackle the huge rod bearing replacement job, and wanted some objective data to guide this decision. The result was that there was some indication of bearing metals in the oil, but at very low levels, not enough to warrant replacement at this time.

I have a new wrinkle in my compression saga, though. I took a close look at my 20-year-old compression tester, and noticed that the o-ring has a sizeable gash in it. So now I'm wondering if this is behind my somewhat low, though extremely uniform readings (174 - 178 psi, the most uniform of any engine I've ever tested). It may also explain the whacky readings I got when I did the test cold. So, maybe I'm getting worried over nothing.

I went ahead and did the Run-Rite treatment, and am following the regimen of specific fuel and oil additives recommended by the Terry Dyson. I've never been a big believer in "better living through chemistry" (kind of strange for a chemical engineer...), but I figure, Terry has been doing this stuff for 30 years, so what can it hurt to try, given that despite the fuel dilution (which his regimen is designed to mitigate), the analysis showed that my engine is not in too bad of shape? Then, after 3000 miles (about another 2500 to go), I'll do another compression check, both with the current tester o-ring, and with a new one, as well as a leak-down check, and another oil analysis. This should give me as complete a picture as possible of the health of my engine, and will take (or not take, as the case may be) whatever action makes the most sense. I'll let everybody know how it turns out, of course.

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[flash]

if your oil pressure shows no real signs of dropping when hot, then your bearings are probably still "ok" - at 107k, they are likely a bit worn, but not likely a problem just yet - if you have any other reason to drop the pan, change the rod bearings

low compression and no oil loss are classic signs of valve train wear - this is extremely common at your mileage

i'm willing to bet now that you will find that your rings are slightly worn, but not worth doing, and that your valve guides are in need of renewal - a simple valve job will restore most of your performance - look at the bright side though - you may not realize it, but at those readings, you are down about 25hp

here is the scary part: when you pull the head, dollars to doughnuts you find the head gasket perforated and eroded - this is apparently happening on 100% of the cars out there, and is due largely to age alone - there will be more info on this coming out very soon - it is being prepared and compiled as we speak, complete with photos and such

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[Cloud9...68]

<!--quoteo(post=73913:date=Jun 14 2009, 12:45 PM:name=flash)-->QUOTE (flash @ Jun 14 2009, 12:45 PM) <{POST_SNAPBACK}><!--quotec-->if your oil pressure shows no real signs of dropping when hot, then your bearings are probably still "ok" - at 107k, they are likely a bit worn, but not likely a problem just yet - if you have any other reason to drop the pan, change the rod bearings

low compression and no oil loss are classic signs of valve train wear - this is extremely common at your mileage

i'm willing to bet now that you will find that your rings are slightly worn, but not worth doing, and that your valve guides are in need of renewal - a simple valve job will restore most of your performance - look at the bright side though - you may not realize it, but at those readings, you are down about 25hp

here is the scary part: when you pull the head, dollars to doughnuts you find the head gasket perforated and eroded - this is apparently happening on 100% of the cars out there, and is due largely to age alone - there will be more info on this coming out very soon - it is being prepared and compiled as we speak, complete with photos and such<!--QuoteEnd--><!--QuoteEEnd-->
Yup, this is a fair assessment. I do think the oil analysis pointed out a few things of interest (air filter element in need of cleaning, no coolant getting into the oil, in addition to my primary question of the degree of bearing wear), so I think it was worth it. And yes, I read DS968 observation of this head gasket, so I would expect mine to be in comparable shape (yikes!). So, at some point in the not-too-distant-future, I will at a minimum need a head freshening. How much else I need/want to do at the same time is going to depend on the rate of growth of my wife's new business, and the continued recovery of the stock market off its lows (a much less certain prospect, for sure...).

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[xrad]

at least oil analysis is one step better than a fortune cookie....or maybe not....

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