Average Engine Oil Consumption

[Joe C.]

All:

My 1965 327/365 engine does not smoke, the R44 plugs are clean, with light tan insulators. The engine has 700 miles on a rebuild, and uses Shell Rotella 15W-40 oil. The reproduction, "correct" tapered end dipstick tube is fully seated in the block, but reads 3/8" below the full mark with 6 quarts, with the old type filter can. I made the mistake of adding an additional 1/2 quart to bring the level to "full", but I will shorten the tube by 3/8" to correct the low reading dipstick.

All of this background information leads to my point..........the engine uses about 1 quart every 500 miles (with the 1/2 quart overfill, which is probably not enough to affect engine operation). About half of this is highway mileage. Normally, travelling at 70-75 MPH, with 3.70:1 gear means sustained 3500-3800RPM (approximately) cruising.

By way of comparison, my 1985 uses 1 quart, about every 3000 miles, but cruises at about half the engine speed of the 1965. That translates to 1 quart every 1000 miles for the '65 if it had the 1985 gearing and overdrive.

So, how does this look? I would like to hear about some of your oil consumption amounts, for comparison.

Thanks in advance.

Joe

[John O.]

Re: Average Engine Oil Consumption

Hi Joe

I'm no expert but your engine should not be using (losing) oil unless there is a problem.To use one quart in 500 miles is not right.You may be burning oil while driving and not knowing it. Rings might not be set right or valve seals etc.Or you may have a small leak some where. My pickup truck did the same thing. No smoke but used oil.I would like to hear what others say since i'm going to be driving my 62 vette in the summer of 06 and that engine is a newly rebuilt 327.

Good luck......John

[Mike M.]

Re: Average Engine Oil Consumption

did your "break-in" the freshly rebuilt engine before taking it out on the interstate at sustained 3000+ RPMs? if you didn't, the rings may well not have seated to the cylinder walls. i usually fire-up a freshly rebuilt engine, back the car out of the garage, then let it run at about 2500 RPM for 20 to 30 minutes before taking the old vette out on highways. mike

[mike cobine]

Re: Average Engine Oil Consumption

Ok, count me confused. How do you know it burns a quart every 500 miles if all you have on it is 700 miles?

At 700 miles, you should be out of your break-in period, IF you remembered there was such a thing. If not, your oil consumption will never improve.

All new cars (i.e., new engines) of the time stated to drive in a certain manner to break in the engine. The involved easy driving and slowly increasing speeds as the miles were added. Basically, you kept RPM lower the first 100 miles, increased them some the next and the next until by 500 miles, you were running at whatever you wanted. No jackrabbit starts, no crashing downshifts, no racing, etc.

Now whether that was the best way or not is debateable. I never broke in a race motor that way, but we never expected to get 100,000 miles out of it either. The ones I got the very best street use out of were brought up in RPM in increments over the first 500 miles to reach redline. I also did easy downshifts and engine braking to put pressure on the rings from the other direction. Those engines frequently went 150,000 miles or more, often to 50,000 or more before noticable oil consumption.

A quart in an oil change is usually still considered normal by most people, i.e., 3500 miles. However, with today's engine building, there is no reason to expect much less, like almost none.

Overfilling can increase consumption, as it can get whipped up into the cylinders by the crank. Put in the right amount for the engine and pan and don't add more. Now if you have an oil cooler or other items, then you have to add accordingly. Check your dipstick with some known good ones. A tube and stick must be matched, but most will work with the block if on the same side (driver side vs pass side) as they measure from the block down and are pan-independent.

Tan plugs in today's gas means you are burning something. Without lead, most of the color indications are gone. Tan usually means too much gas, which could wash the cylinder walls and increase oil consumption.

My '79 is doing about 1-1/2 quarts in a change, but it leaks and has about 80,000 miles. Ihave little knowledge of its previous life, so that is acceptable.

If you had a big block, a quart in 500 is about the norm. Some of them I have seen, you needed to stop for oil before stopping for gas. The 454 in my truck is an oddball - if you run it at 75-80 mph, the gas mileage goes up and the oil consumption goes down, the opposite of many engines.

[Barry Chappell]

Re: Average Engine Oil Consumption

There are facts that need to be discussed first before anyone can determine if there is a problem.
Does the engine have 11:1 CR ?
Are the pistons forged ?
What is the piston/wall clearance ?
What type of rings ?
Are the rings fitted ?
Was the block bored ?
Etc.

I purchased my '70 new, 11:1 cr, 3:70 gear.
It's average oil consumption was always around 700-800 miles per qt.

I rebuilt the engine a few years ago.
30 over, forged 11:1, fitted sealed power moly rings, .004 piston/wall.
My consumption is now about 1,000 mi/qt.
I consider this good for this engine.

500 miles/qt on a re-ringed engine with forged, 11:1, 3:70 is not unlikely.
(If that is the configuration)

A side note, check in on the Cadillac site and check the topics regarding oil consumption on the Northstar engines. 300 hp from 279 cu in.
These engines use oil.
Barry

[Mike McKown]

Re: Average Engine Oil Consumption

You should expect at least 2000 miles to a quart of oil if you rebuilt to original specs. Maybe 3000 miles.

[Joe C.]

That's Not True

"Tan plugs in today's gas means you are burning something. Without lead, most of the color indications are gone. Tan usually means too much gas, which could wash the cylinder walls and increase oil consumption."

The engine is indeed "burning something". It is the hydrocarbon commonly known as "unleaded gasoline". The tan is caused by the particulate byproduct of that combustion.

Lead deposits are white, and build up heavily on the electrodes, during normal usage. If you remember, usually by 15,000 miles, or so, the electrodes, especially the negative, usually had a good sized coating of white material on them. A light tan insulator indicates clean burning, and a good mixture. Black soot means too rich. White means too lean. Black-and-wet usually means oil fouled.

I broke in the motor in the standard way: 20-25 minutes @ 2000 RPM for initial startup. Then drove it "easy" for the first 300-400 miles. Only took the long highway trip after about 500 miles. Before that, just short highway trips of under 20 miles. Also tried to vary the engine speed as much as possible during the first few hundred miles.

Joe

[Joe C.]

Re: Average Engine Oil Consumption

Mike:

Yes, I did all of that. See my response to Mike Cobine, below.
I'm sure that the extra 1/2 quart is not causing any frothing of the oil, but I'll shorten the tube by 3/8" to match a "full" reading with 6 quarts.

Joe

[Joe L.]

Re: Average Engine Oil Consumption

Joe-----

The oil consumption sounds somewhat high to me. However, if you used forged pistons, then I'd say it's about right. If you used cast pistons, I think it's too high.

By the way, if you used modern, high quality piston rings (like Federal Mogul/Sealed Power with molybdenum-filled top ring), these rings are pre-lapped at the factory and do not require any special break-in procedure. It's not a bad idea to use the old-fashioned break-in procedure (it certainly won't hurt anything), but it's not required for effective piston ring sealing.

[Joe C.]

Re: Average Engine Oil Consumption

Joe:

Thanks for the response. I did use Federal Mogul "Sealed Power" rings, pistons, and many other internal components. The pistons are "L2166NF-30" .030" over, forged aluminum, with 5.3cc domes. The rings are iron, "E-251X-30".

Run-in and break-in was per my response to Mike, above.

Joe

[Michael H.]

Re: Average Engine Oil Consumption

Joe,

Unless I missed it, I didn't see any discussion about cylinder prep. I'm assuming your engine builder did use an automatic feed precision hone? There are still several builders out there today that think they can properly prepare the finish using a manual hand operated hone and some still believe they need a "rough finish" to assist the ring break in period. Did your builder give you any info on this?

The 64 365 HP coupe that I purchased new would go almost 1000 miles before needing a quart of oil. That wasn't the case for the first 1000 miles though, as things were still getting settled inside the motor but that was 40 years ago and ring/bore finish technology has come a LONG way in 40 years. There really isn't a break in period now. Fresh motors should have good ring seat and oil control within the first half hour, or less. Todays rings have a soft filler on the face that conforms to the wall surface almost immediately on start up but they are also designed to be used with a smooth bore finish. A rough finish would quickly destroy the ring.

Also, a "too rich" fuel mixture can cause slightly higher oil consumption than normal. Have you had any "issues" with the Holley carburetor? Another point is the way the engine is operated. If you are working it hard, it will likely use the amount of oil that you mentioned, and more.

I would put a few more miles on the car and see if consumption tapers off. Good luck...

Michael

[Mike McKown]

I have never seen Ford or Chevrolet publish any

customer target expectations for oil usage. Bad move politically back in the 60's. Maybe, today, too. Ford did halfway admit that the customer "might" have a problem if he was experiencing using more than 1 quart per 600 miles. This was '60's era, chrome rings, cast pistons, and tight clearances.

I can't tell you what to expect with all the modern machining and parts to expect with regard to oil usage. A long time ago, I re-reringed a 265 that had 95,000 miles on it I had 120 louvers punched in the hood. Oil was pouring out 60 of them on the right side. Chrome rings, no overbore, just used a glaze buster on it. 1500 miles/quart. Before re-ring and broken rings, it didn't use that much.

There was a TSB in about '63 that talked about customer complaints of oil consumption when Chevrolet went to the recommended 6000 mile oil change from 3000/4000. Seems people weren't used to adding oil between changes which prior to this were recommended to be 3000/4000 miles. So they thought they were using too much oil. That was the old days.

Today, it is common to use a quart of oil about every 7000/10,000 miles on my new Fords. Chevy's are probably the same.

I'd say if you overhauled your 327 using the local machine shop tolerances and you get 3000 miles to a quart, you're doing well.

[Joe C.]

Re: Average Engine Oil Consumption

Michael,

The Holley is working great on a Jerry Luck restoration. Mixture is nice and clean. It is jetted per factory specs.
I don't know how the cylinder bores were prepped by the machine shop, but it is a reputable shop. They went so far as to balance the rotating assembly, so I must assume that they are equipped to do the proper honing.
When the block came back from the machine shop, I re flushed the coolant passages again, just to make sure that everything was clean. I didn't take care to remove all the water, and neglected to oil the bores. Next day there was a light coat of rust on all the bores. I cleaned them up with "000" steel wool in a crosshatch fashion. I then lightly coated the bores with assembly lube before measuring and installing the pistons.
Hopefully the consumption will decrease a bit over the next 500 miles, or so.

Joe