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2.5L Oil Consumption. What's typical?


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When I first bought my MJ I had oil leaking out of every orafice the truck had. After fixing the PCV system and replacing a lot of gaskets most of the leaks have dried up (still minor seepage from rear main and oil pan gasket). Since that time I've been watching the oil consumption and it seems a bit high. In an average week (40 mile daily commute, highway @ 75mph) I end up using 12-16oz of oil. The engine does have enough blowby that I have to replace the air filter every 8-10K but, other than that she runs fine. I wanted to see what kind of oil consumption is considered typical or at least average for the little AMC 150.

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You didn't state your mileage however I assume it 200k+ being an 87. My 91 had 230k+ on the clock and consumed about 1qt every month from blowby and worn rings. Sounds like time for a rebuild but I'd pull your valve cover and inspect it unless you already did. Mine was completely clogged with gunk. Never hurts to do a compression test either.

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Is that 40 miles one-way, or round trip? Either way, that works out to half a quart in either 200 miles or 400 miles, which is a quart in 400 or 800 miles.

 

In general, a quart in 1000 miles is about normal for an older engine. A quart in 500 miles or less is excessive.

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It's 40 miles round trip (1 qt oil consumption every 500 miles) and I had the valve cover off last year to replace the lifters & pushrods (had a bad lifter). It wasn't excessively gunked up but it did have hunks of carbon, etc inside. It looked like the PO was bad about routine maintenance. She just turned 196K.

What's the acceptable limit on a compression test? Is it best with the engine warmed up or cold?

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Someone told me a while back that a stretched timing chain/belt can lead to really bad blowby. I've yet to test out this theory (mine doesn't move much these days, but was consuming a whole heck of a lot when last she saw freeway time), but if your compression results are fine (mine were acceptable) then you might want to look into it.

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I'll have to do a compression test and check it out. Warm engine or cold?

I did check the timing with a timing light and it wasn't jumping all over the place so I think the chain is ok. Granted I couldn't disconnect the electronic spark advance (my '93 Chevy pickup had a plug for the EST control) but I would think that I'd see the pointer dancing around regardless. It is noisy at idle but, then again, the 150 isn't a really refined engine from a NVH perspective to start with.

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