low oil consumption

my engine (160 hp o-320) uses 1 guart oil per 20 to 30 hours. cylinders are not chromed.oil analysis has always came back normal. my last compression check was 80/80 all cylinders. engine has 500 tach hours since overhaul.the last 15 hours (all cross country) it used less then 1/2 guart.is this abnormal? my cross country cruise is usualy at 2600rpm and 8000 to 13500 msl. what is causing the very low oil consuption? will high altitude cruise result in less oil consumption? anyone experienced this? thanks..lawrence..

Celebrate

Sounds like you have an exceptional engine! Go celebrate with a nice cold one

Regards,

Well NOT so fast, could be (may be) an issue

lawrence said:

my engine (160 hp o-320) uses 1 guart oil per 20 to 30 hours. cylinders are not chromed.oil analysis has always came back normal. my last compression check was 80/80 all cylinders. engine has 500 tach hours since overhaul.the last 15 hours (all cross country) it used less then 1/2 guart.is this abnormal? my cross country cruise is usually at 2600rpm and 8000 to 13500 msl. what is causing the very low oil consumption? will high altitude cruise result in less oil consumption? anyone experienced this? thanks..lawrence..

Click to expand...

The 20 to 30 hours is pretty wide, 30 I'd be slightly worried and investigate. Than you say less than 1/2 qt in 15, which we could extrapolate to the +30 hrs per qt. ???? 20 sounds on the high end, 30 crazy (impossible) for a 500 hour engine in my experience. Could it be the way your are measuing it? Could your buddies be putting oil in your plane at night to punk you? (That would be funny) (what is your oil temp and pressure?)

Also what power setting. At super low power settings you will burn less oil. DO you run 75% or 45% power?

I use to think less was better with oil use, but actually not from what I read if its extreme. Sorry, don't recall exact detail's; the gist is not using oil means it's not getting where it's needed. I recall it has to do with Oil Control Rings. However it usually turns up early after rebuild, not 500 hours later.

Now before I panic you, obviously you are asking so you have some concern, The 80/80 sounds odd? I mean that is great, but its theoretically possible but not likely in a 500 hour engine. LOW OIL USE and SUPER HIGH COMPRESSION seem to go hand in hand.

Extreme low oil COULD (may be) be a sign of trouble. However since you have 500 hours, all is well, oil pressure good, oil temp good, compression good, I doubt you have a problem. It could indeed be you have a super tight engine (?).

May be some engine gurus who are smarter than I about the topic.

1 qt in 20 hours sounds reasonable for a super tight engine. I have seen 16-18 engines with 500-1000 hours. Also I guess you are keeping the oil at or below 6 qts. 30 qts per hr sounds too low and could be just your way of measuring. I could see you being off a few hours but not 10 hrs. So 20 hours super, 30 suspicious.

If you want to use oil fill the case up to 7 or 8 qts and it should blow it out fairly quickly, but I am really not recommending that. However it would confirm you breather is working. If the breather is not well you can blow the front seal out and cause a massive oil leak. Make sure your breather is working, clear and not being pressurized. The tip of the breather TUBE is usually cut on a diagonal and facing into the local air flow like this: >> \|

Just be sure you consistently measure the oil on a level surface, after the engine has shut down and the engine cooled (oil drained back to sump). Check oil level the same way and in the same state every time. I scored my dip stick very precisely with a pipe cutter and only add small quantities at one time, as little as 4 ozs. My goal was keep it around 6.1 to 5.8 qts.

Consider oil analysis, another comp check, monitor oil use closely and write it down. It is what it is. Good Luck, but 30 hours per hour sounds low.

Low Oil Consumption

Lawrence,

My factory new Lycoming O-320 with 300 hrs on it has never used much oil.
I am using Aeroshell 15-50 and never cruise at more than 65% power, which might explain my low oil consumption of half a litre ( 1/2 US Qt) between 35 hr oil changes. I also do not fill beyond 6.5 qts, and try to maintain around 6 qts in the sump. My oil analysies show normal wear - a little higher on copper but less on everything else. If I was concerned about not using enough oil, I would be at a loss to know what to do. I figure low oil consumption to be a good thing rather than something to be concerned about, but willing to listen to any theories...

Cheers

Martin in Oz

Some factory new TCM engines use <1qt in between 50hr oil changes. I wouldn't worry.

i changed oil yesterday at 25 tach hours.and sent oil sample for analysis.oil level was 6.1 quarts. i always refill with 7 quarts aeroshell 15/50. the 80/80 on all cylinders was the first time compression was this high. usually 80/77 is a typical cylinder, maybe one will be at 80/80. the 30 hours per quart statement was based on the using 1/2 quart on a 15 hour round trip at higher altitudes.based on fuel burn,power setting was 60-to 65 percent. thanks for replys....lawrence...

And here I was getting excited about 77/80 and 78/80 at the first service. I am using a quart every ten hours, but run at 25/25 which is 80% and burn 11.5 GPH at this setting . 2000ft 160 knots indicated. EJ

RV6 O320D2B CS Prop oil use

My oil use is so minimal that I barely pay attention. On a round trip South FL to OSH trip some 25-30 hours, probably add 1 qt., and never filling over 7 qts. Over 7 qts and you just blow it out of breather, at least on my model Lyc. This is not an indication of blow by, but simply a function of design, breather location. Can get oil-air separator to solve this I suppose, but oil is cheaper. Aeroshell 100W AD SAE 50. Compressions all mid to high 70's.