I was wondering how much oil usage is acceptable. I have a rebuilt 403 with around 9.5:1 compression and a mild-ish cam. It had about 40,000 miles on the rebuild and its using about a quart of oil every 2500 miles. It that nornal or should i be concerned?

 

I wouldn't like that, but I would accept it.

In the past, some new car warranties would consider that normal. One quart per/3000mi. oil change as acceptable. Of course they didn't want to pay out for something wrong.

As a car guy I would want to know why.

Things that come to mind:
oil leak
valve guide clearances
valve seals
piston rings/bore clearances excessive
Also, wouldn't hurt to make sure your PCV system is intact and working.


The oil usage is coming from some where.

If it were me, I might start with having a buddy follow me cruising and giving the old car a good ride. Get his tail pipe observations. Seriously.

 

I dunno, a quart every 2,500 miles sounds pretty darned good to me.

I'm curious to hear others' experiences - I suspect these engines, when low mileage or rebuilt, and in good condition, average a quart every 1,500-2,000 miles

- Eric

 

Agreed, check for leaks first. A small leak at the back of the intake or even from a back bolt of a valve cover can actually burn off on the exhaust and not drip to the ground, so it's hard to tell it's even leaking.

And how do you drive? Are you on the highway a lot? 2500 miles for a quart isn't bad at all. Especially if you're romping on it occasionally, or more.

You might be getting oil up through the pcv valve too. Over that many miles, even the mist adds up.

I don't think it's anything to be concerned about.

 

My last job, the boss's son lease a brand new 380ZX. Every oil change he will lose 1-2 quarts of oil every time I change his oil. He talked to Nissan and they told him that particular engine will lose oil and this is normal regardless how you drive as long he changes his oil every 3000 miles. I will drive behind him and there's no blue smoke coming out of the tailpipe and no oil leaks. Go figure.

 

The 'stone' Y-code I had in an 86 buick wagon drank 1qt per tank of gas. I used to keep a case of walmart oil in the stash box

Bores oval and rings stuck?

 

That isn't using oil too fast. Now, if I had a late model car using oil that fast it would be a different thing.

 

You mean 370z?

 

I dont do much highway driving but i like to beat on it every now and then. I looked the engine over and i suspect the pcv. There is a little bit of oil that seems to be coming out of the valve cover breather. I put my finger over the pcv valve and it feels like its working, but maybe i should replace it anyway.

 

My bad, I just texted him. He said its a 350Z.

 

Funny. I bought a 70 4 dr Galixie with a 429 from a bud's parents that we got hot after a water pump gave out on the way home from somewhere back in my highschool years. We got it home and was able to cool it down before shutting it down. Burned the rings out but it would still go after a new w/p.

Smoke! Let me tell ya... I used to carry drip-oil in the trunk by the 5 gal. bucket. I remember his Mom telling him to go put new mufflers on it. He took it to the shop and had the boys put 10" Cherrybombs on it, ha. His Mom hated that car after that. He burn't it up, I bought for $50. Spent probably $12.50 on a pump, and drove the crap out of it for a while longer.

 

They seem to leak a little, no matter what you do. It's not necessarily the pcv valve being bad. I tend to wipe the valve covers down with a soft cloth every week or so, and I usually get a little bit, not enough to be concerned about, but it's not a perfect system.

Higher rpms, you're bound to pull a little bit of oil through the pcv valve.


haha, gotcha.