What’s is considered acceptable oil consumption for an old cat?

Thats a little excessive. Sounds like it may be time for sleeves and rings. If it was valves it would start hard and spit and sputter when cold starting. If you do decide to overhaul then have the heads checked anyway. Blowback from the filler tube is normal when adding oil when engine is running, just have to pour oil in fast and put the cap on quickly.

Different grades and brands of oil can also impact on oil consumption, I had a 270 D8H that had a rebuilt motor when I purchased it, it used 5 liters every 10 hour shift right from oil change to next oil change, was using series 3 30 as recommended, one oil change I used series 3 15w 30, oil consumption dropped off to about 10 liters to 250 hour interval, so continued to use it there after. EDB or Old Magnet might have the number, there is a % of oil consumption to fuel consumption ratio that is acceptable before it is deemed time to rebuild an engine, I was told years ago, think it was 2% for these old style engines, it may have been a lesser %, hopefully one of them will chime in with the correct number.

Wombat

Also go heavy with an oil stabilizer.... we run lucas oil stabilizer and it will really slow consumption down and also it will help blow by alittle. we had a stieger with an old cat v8 1160 that would use 2 gallon per tank of fuel while running a ripper even after an overhaul then we started running lucas and consumption droped to near nothing

I probably am at about 1% oil to fuel usage if it’s working real hard. Much less on the easy days. Currently I’m using 30wt diesel oil from a good source. I will try some additive also.
Thanks again.

For what it is worth, I had a great uncle that cut his teeth as an operator in the 1940's and worked on construction and roadbuilding jobs up into the 1980's. About that time my dad had bought an International UD-18 power unit engine for his sawmill, same as what was in the TD-18 crawler tractors of the time. He was a bit concerned about oil consumption and my great uncle told him that they used to let the old diesels of that size go until they burned 2 gallons of oil each day before they'd finally pull it from service and decide what they wanted to do with it (rebuild or replace). That sounds quite excessive to me, but he swore that's what they did. The old UD-18 never burned more than 2 or 3 quarts a day and we ran that unit on the sawmill every summer for 20 years and it never got any worse so we never dug into it to see how badly it was worn. Had blowby but started well with the gas/diesel switchover mechanism and had good power.

Hi Team,
time to break out the popcorn again with the old "what is correct oil for these older engines"
Cat recommended, back in the day and still recommend a Straight 30 Weight Diesel Engine oil for these D300 Series Engines working in Normal temperature and conditions--adjust viscosity as needed for your local temperature.

Multi Grade Oils today have way more additives, BUT, often with less of the vital additive for flat tappet cam followers as they are generally aimed at later designed engines some with roller cam followers.

Basically when Cat released their Multi Grade DEO, Cat said Pre-combustion Chamber Engines are STILL to run Straight 30 Weight Diesel Engine oils--ambient temperature can change that, AND, Direct Injection Engines run Multi Grade Diesel Engine Oils.
An exception to this case in point that I was involved in was a 3208 Low Horsepower Truck engine in a Cat Lift Truck that was using excessive oil.
When I inquired of what oil was being used I was told Cat Multi Grade oils as per the instruction for DI engines---BUT the 3208 was designed before Multi Grade Oil recommendations came in by several years.

The engine was scheduled for removal and overhaul--I suggested to run the good old 30 weight DEO and amazingly the oil consumption cleared up. Sometimes all that is written is not correct--there can be variances as you can see.

Hope this helps.
Cheers,
Eddie B.

like has been said try the oil.
back around 1960 cat used to say give the engine like a teaspoon of Bonomi cleanser to break the glaze on cylinder walls , maybe some old timers can give better info on this.

Also something to remember the early d339's were naturally aspirated with 2 compression rings and 1 oil ring on pistons then they throw a turbo on the same engine with no change to piston design.... also there is no valve guide seals on the heads so naturally these engines are going to use oil

Wow so 2 gallons a day was what a worn out unit used! I don’t feel so bad with my usage at half that. I just wasn’t sure if that was normal or not but it appears that they all used plenty of oil to some degree. Basically I need to add oil at the beginning of every day when I fuel it if it worked hard the day before.