RobertL18C wrote:
Once broken in I operated them at around 55-65% LOP and oil consumption settled down to around a quart every 20 hours. Never had an issue with them over ten years of operating them.
That’s pretty much the oil consumption I see. I change oil every 25h and either don’t add any makeup oil or half a quart.
Peter wrote:
But a lot of engines (the majority) burn 1qt every 3-5hrs!
I’m sure you have statistical evidence. Mind sharing? 
Most IO540 owners I know are burning about 1 in 5hrs.
The other day I spoke to an Aztec pilot (not the crashed one) who said something similar and added that with W80 the oil loss is a lot higher than with W100.
I change oil every 25h and either don’t add any makeup oil or half a quart.
I have realised a possible fallacy there: start the service interval at say 10 and end it at say 7, means you burnt 3 but since you didn’t add any oil, you didn’t add any oil 
And, let’s face it, who is going to add oil just before doing a service at which all the oil will be dumped. Topping it off back to 9 would be a complete waste of 15 quid.
I have records of 50hr service intervals with only 1 or 2 added but really another perhaps 5 was used up. In the old days it was done by the book, adding the maximum (12). When I was G-reg I used a company to do it, 600 quid each time, and that’s what they did.
1 quart every 5 hours on an IO540 seems high, my on condition engines were closer to 1 quart every 6 to 8 hours. Typical legs were around four hours.
I am not sure I would count the first two quarts after an oil service, this tended to go quite quickly. Filling to 9 quarts even on a four or five hour leg was fine.
A T67M I fly will use a quart every 5 hours, but this is on a diet of aerobatics.
I think there may also be an installation factor – the way the breather tube protrudes into the slipstream could dramatically affect the oil loss. The inside of the engine is a totally churned up mixture of air (gases of all kinds) and oil, and the smallest net outflow is going to carry a lot of oil out.
I have already checked my breather has not moved.
Can anyone who has amazingly low oil consumption post photos of the end of their breather pipe and the way it is located?
If you really think you are blowing oil overboard, then I suggest you do a crankcase pressure test.
Do you know how to do that? Nobody around here (UK) that I have ever spoken to has ever heard of such a thing.
That’s not difficult to do but requires some McGyver creativity.
http://www.121five.com/admin/FeatureArticles/Superior_Excessive_Oil.pdf
Now, who has a spare dipstick I can cut the “dipstick” off?
I have saved a local copy of that doc – really handy!
I’ll check around for a dipstick, but you could use something else like some hose and clamps to get a tight fit.
Or you just buy one, they are available without dipstick. In my installation, the oil filler cap is not combined with the dipstick. Last time I checked it was not expensive.
