Anyone know how much oil can be lost due to seals that probably needed to be replaced a while ago, from an early 90's dohc with ~130K miles? Am wondering if the oil loss due to these seals is anywhere near to what the ring situation can cause as far as oil capacity loss?
Or, are the front and rear oil crank seals generally more of a culprit as far as oil loss goes? Trying to shore up the loss....
Unfortunately, pinpointing a single cause is rarely possible with these motors. Numerous people have even reported here that a rebuild/re-ring/new valve stem seals, etc didn't do the job.
Any advice that I'd offer (after owning mine 14 years and counting)... just add oil when it needs it and check it often. Oil consumption isn't necessarily a sign of otherwise impending doom. It just means that a lot of things are well lubricated. :)
Lane [ lane (at) evilplastic.com ]
What is your oil consumption rate? Note that oil (and fuel) consumption rate will increase with increased rpm and increased road speed operation. IMHE, oil consumption rate increases when using bargain brand oils and there is a definite difference in consumption rates between name brand oils. Consumption rates also increase substantially as the oil ages and during hot weather. I keep good records of both fuel and oil consumption and oil brands and suggest that this is a very informative practice. My S1 car with 275k km now uses 1st litre @ 2100km but the second and subsequant additions @ 1300km. I consider this acceptable consumption for a motor of this age.
Sustained long term high temp operation and age can deteriorate valve seals but they are usually good for the life of the valves. Normally, by the time the seals are worn the valve guides and seats will also be worn and the seals are normally replaced any time the valves are reconditioned. Valve train wear is increased substantially by high RPM operation.
Leakage from the front or rear crank seals is usually obvious under the motor or on the ground where the car is normally parked. Placing a large piece of clean cardboard under the motor after a long hot drive may help. Any leakage can consume a LOT of oil, a big leak may often be harder to find as there will be less evidence on the motor as the normal dirty streaks may be removed by the flow of fresh oil.
It has long been known that oil consumption past the rings is often increased after regrinding the valves, this is usually explained by the increased suction during closed throttle engine braking but the raised compression can also lead to increased blowby.
I definitely agree with Lane and would like to reinforce his use of the word OFTEN. I suggest a check EVERY fueling at the MINIMUM or better more often. Leaks and consumption rates can increase dramatically without warning. I would add that oil change intervals should be reduced for engines that burn oil as it will have increased contamination from combustion byproducts and blowby which will significantly reduce the lubrication properties of the oil. Change the oil when you are down to the add mark (NEVER EVER RUN BELOW). IF necessary, you can change your filter every second change but it is preferable to buy your (good quality) filters (and oil) in bulk and change with the oil.
Some here have reported good service and reduced consumption using 10w30 in warm weather and 5w30 in the winter, if you do this be sure to allow a couple of extra minutes (of low speed and load operation) to allow the oil to circulate (to the timing chain) at startup.
Good luck, YMMV
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