oil awfull black

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I have a 1983 Toyota truck 22r, with a ton of miles, starts great and runs good. Smoke a little while coasting in gear slowing down. My oil looks like diesel oil in about a thousand miles, black as tar. Any ideas as what causes this, i appreciate any ideas. Travis.
 
"Smoke a little while coasting in gear slowing down"

Good indication of bad valve guide seals, that will cause exhaust gases to leak past the valve guides seals and make the oil dark, and allow oil to be sucked into the cylinders and cause the smoke.
 
Excessive blow-by. That means you'll need to change the oil more frequently.

As engines age, they have more blow-by. Therefore, IMO, it is a good idea to change the oil more frequently on older engines. Every 3,000 miles is a good interval.
 
if i remember that is a carbeurated engine. i bet its running really rich. 22r is a tough engine.
Check the color of your plugs, if it is not rich then it probably is the valve seals as Bob Woods suggested
 
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Blowby is when the rings are worn enough to let combustion gasses leak by the rings pressurizing the crankcase. This allows carbon and unburnt fuel to contaminate the oil , in severe cases the crankcase is pressurized and blows oil back out the dipstick.
 
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