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Old 04-14-2009, 12:03 PM
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Low compression - synthetic?

I have read posts here about using synthetic oil to help clean out the engine and possibly raise compression. Just wondering if this would be a good idea in my case. The first three cylinders are about 300. The last two around 160. It starts on cold days no problem but is always jumpy until it warms up. Was thinking of trying synthetic to see if this helps as I think car sat awhile before I got it, but would this possibly bring out other problems? I'm about to take this car on 1-2000 mile road trip and don't want to do anything that might cause problems.

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Old 04-14-2009, 12:32 PM
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synthetic oils have been known to stop or greatly reduce oil leaks, for example I screwed up installing the rear main oil seal on my 616 and it leaked a little, after running Amsoil the leak almost stopped. I dont think it will raise 160 # compression to an acceptable level tho. I have freeded up sticking rings causing low compression using something like "Marvel Mystery Oil" and plenty of Itialian tuning up. Any story to go with the 160# reading, strange noises, smoke, over heating/out of oil event? Valves adjusted? Theres allot of good detectives around here
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Old 04-14-2009, 12:34 PM
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What has been done to try and fix the car? Valve adjustment? Leakdown test? Italian tuneup? How much blowby does it have? Does it smoke blue?
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Old 04-14-2009, 12:53 PM
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I did a valve adjustment a few thousand miles ago. Since I got new monarch nozzles haven't had much smoke at all, just a littl white/gray smoke if the car has been sitting awhile. Got the car a year ago and don't know much about it's history and I get the sense it sat awhile. It has a decent amount of blowby. It runs pretty well once warmed up but the engine seems jerky when first started. New motor mounts. I tend to drive it italian style much of the time.
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Old 04-14-2009, 01:03 PM
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While the high detergency of "synthetic" oils can help clean up ring lands, it's not going to relieve a severe case. It sounds like you may be at the point where a hammer and chisel are needed to clean out years of accumulation, Felix.

I suppose there's not much risk at trying. Your most economical choice will be Rotella's Syn 5W40. Many folks run this oil in their old 5cyl cars with good results. It's a modern all season/all climate oil.

Good luck.
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Old 04-14-2009, 01:06 PM
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It's a modern all season/all climate dino oil made to act somewhat like synthetic.
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Old 04-14-2009, 01:07 PM
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A little white smoke?

White in the tailpipe smoke indicates coolant in the combustion. Are you down in coolant once in a while. Also, with three good cylinders up front, then two adjoining cylinders at the back showing only a little more then 50% of the compression of the others, I think you might suspect a head gasket leak between those cylinders. I think you should pull the head and find out before you get too far from home.
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Old 04-14-2009, 01:11 PM
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Quote:
Originally Posted by junqueyardjim View Post
White in the tailpipe smoke indicates coolant in the combustion.
As well as condensation from the air and normal cold combustion.
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Old 04-14-2009, 10:09 PM
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my coolant level stays pretty solid, as does my oil. maybe i ought to test these numbers again to make sure, try synthetic and see if it does anything. i guess it's worth a shot. next oil change i'll do an analysis as well. don't want to turn this into an oil debate thread, but do you recommend rotella just because its cheaper or you think it's better? i read lots of recommendations for mobil delvac 1 for cleaning things out.
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Old 04-14-2009, 10:28 PM
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another thought

not sure if this is relevant, but my car has been running somewhere around 173º F most of the winter, which seems little low.

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