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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

Reasons compression is dropping

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Old Jun 26, 2015 | 02:27 PM
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Eddillard79
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Reasons compression is dropping

Hello. I have a 1985 f350 w/460. I've owned the truck for almost 2 years now. I'm noticing that my engine compression gauge is slowly getting lower as time goes by. My engine still runs good, and pulls whatever.

When I first got the truck, my gauge would stay at the "m" in the "normal" range. Now it's stays at the "o".

Should I be worried, and what could be causing this? I'm scared that if the compression gets to low, I won't be able to get it normal again.
 
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Old Jun 26, 2015 | 04:31 PM
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What weight oil are you running? Also what brand?
 
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Old Jun 26, 2015 | 05:46 PM
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That isn't a "compression" gauge. It is your oil pressure gauge. And the factory gauges are notorious for being inaccurate, so most guys add aftermarket gauges to get a good reading on oil pressure, coolant temp, and battery charge.

But, your oil pressure will go down as the outside temp comes up. And it will go down as the miles add up on the oil in the engine. Or, for that matter, it can go really low if you are low on oil.
 
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Old Jun 26, 2015 | 05:53 PM
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Well that makes complete sense now that I know what kind of gauge it is. I use 10w-30 oil. But I'm due for an oil change also.
 
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