Oil Consumption 600 mi/QT no smoke

[kyngfish]

Hi All,

My engine has 84k miles, no smoke on startup, no smoke on revs, driven daily about 40 miles per day, no visible oil leaks although I have some weeping on the valve covers.

When cold, I idle at around 3 bar, and at any reasonable revs i have 5 bar of pressure. When hot I get 1 bar at idle and 4.5 at about 3.5k RPM.

Since my last oil change about 2100 miles ago, I've added 2.5 quarts of oil and I'm siting about 1/5th of the way up the dipstick, so I guess that means I've burned through about 3.5 quarts. (I guess a little less, since there's still about 1/5th over the MIN mark).

Once again, I get ZERO smoke. I'll do a leak down test and pull the plugs as soon as I finish grad school in a month, but should I check for anything else?

Does daily driving in mixed traffic affect oil consumption?

[VFR750]

Just because there isn't a billowing cloud of smoke doesn't mean you are not burning oil. It just means it is burning at a low enough rate that you can't really see it.

But if you shine a bright light through the exhaust at night, you will likely see the tint in the exhaust.

Your consumption is high but not terribly so. At 84k the valve guides may be loose enough to allow more oil past them. Your rings are likely wearing and passing more oil. Basically an old engine.

You could remove the spark plugs to see of they are wet and have carbon build up. That would confirm the oil burning and likely culprit is the rings. Less likely the intake valve guides.

Even then, 600 miles per quart is high but not too high. Not yet.

Keep an eye on it and start recording the dipstick reading and mileage. Also add quarts as needed.

If the consumption stays constant you can probably run it that way for a long time. Just adding quarts as you go.

I did that for 6+ years and 20,000 miles or so. Only at the end was the oil smoke noticeable. And then it's a full rebuild.

[VFR750]

High, sustained rpm, will increase the oil consumption. Track use even more so. Normal street driving should consume very little oil.

[Reiver]

I had the same on an '83 930-16 SC....had 230k miles unopened. Ran well too. Using a quart about 550-700 miles give or take...it had decent leak down numbers too.
The only time I saw a puff of smoke was on very high rpm deceleration (vacuum) that indicated valve guides/seals were partially the issue. This I had to execute and watch for as otherwise no oil smoke.
I got very tired of feeding it knowing a rebuild was in my future.
Swapped it for a 930-10 '83 Euro that had a recent top end/no bottom end (76K on the bottom).
Now I burn about 6 to 8 oz. of oil between 3k oil changes.
The difference between good tolerances and worn tolerances.
I'm guessing yours is a 3.2 Carrera, they are known for low miles guide wear.

[LakeCleElum]

What year is your 911? Factory claims one liter per 1,000 K's (600 miles) is acceptable....Ck leakdown and compression. Budget for a top end job in the next few years is my guess...Your oil pressure sounds acceptable to leave the bottom end alone....

[Reiver]

Originally Posted by LakeCleElum

What year is your 911? Factory claims one liter per 1,000 K's (600 miles) is acceptable....Ck leakdown and compression. Budget for a top end job in the next few years is my guess...Your oil pressure sounds acceptable to leave the bottom end alone....

I'd agree for a high mileage car like mine in the example I posted but 84K....he's got serious valve guide wear or worse for those figures unless he's always driving at wot.
Porsche was covering their azz with that comment.

[LakeCleElum]

Originally Posted by Reiver

I'd agree for a high mileage car like mine in the example I posted but 84K....he's got serious valve guide wear or worse for those figures unless he's always driving at wot.
Porsche was covering their azz with that comment.

Agree with you for sure Reiver....84K should be driving like new...

[kyngfish]

It's an 86 coupe, drives fine, that's the thing, I get ZERO smoke. Occasionally if it rains, there's very slight condensation smoke, but on deceleration, everything, runs clean, the engine is clean, PPI was fine, but to be fair, I didn't do a leak down.

I drive it every day in the heat, 40 miles per day, and I was wondering if that might contribute to consumption.

I'm going to take a week off when I graduate from graduate school and I'll pull the plugs and do the cap and rotors and maybe a valve adjust, but in case I need to budget for a rebuild, I wanted to see how long I have.

[cgarr]

You still running a cat? If so take that off and you will see the smoke!

[Reiver]

Originally Posted by cgarr

You still running a cat? If so take that off and you will see the smoke!

Yeah, what he said.....I removed my cat and still didn't see smoke at idle with 230k miles and 600 per quart.
I did see it on sharp decal tho with the vacuum....guides pulling the oil in.
3.2's are known for this...early valve guide wear....loose valves can lead to other issues too btw. (do a search)
You won't see this at leak down as the valves are closed...your rings are prob. fine....that was my same experience even at 230k on the SC...rings were still in spec.
What a motor huh.

[kyngfish]

So does that mean I should do a I'll top end or just replace the valve guides? Can I test the valve guides when I adjust the valves?

[Jesse16]

To my knowledge, you can't just replace the valve guides. I believe your choice is to do the smart thing and simply add oil till the smoke comes soon or many years down the road or spend a bunch of money to do a top end to avoid adding (as much) oil. Sounds like after spending the money, you would notice no difference! If I were you, I'd add oil and be happy your motor is clean and running well and not annoying the population with visible smoke. You will always check and add oil as needed to these engines.
My 87 has nearly 70k since its rebuild (at 180K) and uses about 1 qt per 1000 miles.
Clean as a whistle plugs, motor, exhaust and no cat. Some slight smoke after sitting awhile and started.

[Drisump]

No one seems to asking where you keep the oil level on the stick? These cars definitely burn a lot more oil above the mid point on the stick. My 3.2 @105k miles consumes less than a quart every 2000 miles if I treat mid point as full. When I first bought the car @70k miles, it consumed a quart every fhousand miles or so because I fussed over maintaining the level at max on the stick. As far as I am aware, all the gurus on this forum and the Pelican one, recommend mid stick as max on these cars. Steve Weiner has even started threads on the topic. Do not concern yourself about not having that single quart or so from mid point to max....there are 12 more. Enjoy the season

[Drisump]

On these cars, a "top end" is usually valve guides. The shop will drop the engine, pull the heads, remove the quides, replace the guides, inspect valves/seats and seat them properly. It's a good chunk of money but in my mind, get it done right!

[kyngfish]

Ooooook! Seems like I have the information I need. I've been saving some money anyway just in case the car needed anything. I live in Miami, can anyone recommend the best place to do it in South Florida, and how much I should budget? Since I'm still at 600 miles per quart I probably still have a little time, but I might as well do my research now.

RE: Dipstick, I keep it under halfway. That's pretty much how I measure the quart.

[RSTarga]

What weight oil are you using? Try a 15w-50 or 20w-50

[kyngfish]

brad penn 20w50

[Nick Triesch]

What?? 600 miles a QT and your plugs are clean!!!!! Just drive it for 5 more years and save the $3500-$5000! My car has 150,000 , uses a Qt ever 600 miles , plugs are very clean and I just passed my 3rd California smog check!!!

[Reiver]

Originally Posted by Nick Triesch

What?? 600 miles a QT and your plugs are clean!!!!! Just drive it for 5 more years and save the $3500-$5000! My car has 150,000 , uses a Qt ever 600 miles , plugs are very clean and I just passed my 3rd California smog check!!!

There is that approach too...and it may work fine for some years.
The next time you have your valves adjusted have the mechanic check the play (side to side) in the valves and see what he says about the wear.
If it looks acceptable just drive it and monitor your usage, if it drops off exponentially then you know the deal.
Overly worn guides can lead to other issues but you may not be there yet.
Kind of a call that needs to be made with a bit more looking...luck with it.

[Josh D]

As another point of reference, my burn rate is in the 600-700/qt range, 135K miles, I have one confirmed worn exhaust valve guide (#2), it runs an early exhaust (no cat), great leakdown numbers and does not smoke.

I'm currently collecting parts to do a top end including P&C's for a 3.2ss.