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Old 06 Feb 2010, 02:43 pm
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Matt42 Matt42 is offline
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Join Date: Jun 2009
Location: Glendale, AZ
Posts: 496
Default Re: Synthetic oil or conventional oil?

Originally Posted by perkl View Post
i bought a 2003 chevy venture van with 85,000 miles on it owner used synthetic oil so im continuing using synthetic oil my question is it common for synthetic oil to use a quart every 1000 miles .as it does like clockwork.there is no leaks and no blue smoke out of the exhaust ?
Probably not. The oil consumption is more likely to be a function of loose tolerances within the engine, or the PCV (positive crankcase ventilation) system malfunctioning a little and sucking too much air out of the valve cover. (Or both.) A simple test would be to use regular "dino" oil on one change. Switching back and forth between regular ("dino") and synthetic is not an issue--I do it a lot, and I even mix them. If it still burns oil, it wasn't the synthetic oil that caused the problem.

BUT, it is very unlikely that the synthetic oil would be the problem. Synthetic oil has a higher flash point than regular oil. That means that the cylinder temperature needs to be higher to burn off synthetic than it does to burn off regular oil. I have cured oil-burning problems in other people's vehicles used for heavy towing by switching to synthetic. In one example, the pull from San Dimas, CA to Barstow, CA using a Ford F-250 360 V8 pulling a 5th wheel trailer used to burn one quart of normal 10W-40 over that distance, which included the grade up Cajon Pass. Switching to 10W-40 synthetic stopped the oil burning because of the synthetic's higher flash point.

Burning a quart every 1,000 miles won't produce blue smoke you can see. Once you get to a quart every 300 miles or so, then you can see it.
1996 Dodge diesel 4X4, 2001 PT Cruiser Touring with rear disc brakes, [Now gone 2004 PT Cruiser Base 5 speed], 2007 Chrysler T&C Touring
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