How much oil should my truck use?

[ch1ch2]

I don't want to quibble, but wouldn't 0.5% of 100 gal. be one half gallon, or two quarts?

Not to quibble either but 0.5 of a gallon would be 1/2 a gallon. 0.5% would be 1/200 of a gallon. 5.0% would be 1/20 of a gallon. Move the decimal in front of the 5 would add a zero.

 

[STx]

My factory remanned 12.7L Detroit 60 with 560,000 miles on the reman uses about 2 qts in 22,500 mile OCI's. So I would have to say that not all turbos and diesels use oil. That engine was on 15w40 syn blend for quite a while, but has been getting 10w30 syn blend for about a year. Same oil consumption with either oil. The Cummins ISX 15L I had before used, maybe, 1 gallon in 25,000 miles at 968,000 miles. Next owner put it right to work. My worse offender... a '96 Cummins N-14.. used about a gallon in 7000-8000 miles. But then, it had 1.4 million miles on it and only repairs to the motor were one injector and an accessory drive seal. Same thing... it went right to work for the next owner. While OEM's and others might throw out what is considered "normal", I am not so inclined to believe them.

Picked up on a 2006 Cadillac CTS 3.6 with 52,000 miles a few weeks ago and in immaculate condition. Lots of folks claim these motors "use" a lot of oil, and they do. Read all kinds of 1 qt in 1000-1500 mile stories and that it is "normal". But I cleaned the MAF and Throttle Body, did a CRC Intake Valve Cleaner job on the top side, did an engine oil flush and changed oil and filter. The kicker was, I put on a Elite Engineering PCV oil catch can on the engine. I think I found where the oil is going that they are "using". This is the result of just one week / 240 miles, almost 2 oz. Getting sucked thru the PCV tube is not my idea of "using" oil by the engine. The level of what the Elite can captures virtually mirrors what the engine is "using". So essentially, the engine is actually nice and tight and not using any oil at all. But it is "consuming" it.

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That's the issue with both of mine, the crank case is vented back into the intake and because the crankcase is pressurized by the turbo, it'll push some oil through that vent. I removed that intake vent on the 7.3 (which also uses oil to drive the injectors) and vented it to atmosphere like International does with the big brother trucks using the same engine, it still consumes some oil but I don't have the carbon and gunk buildup in the intake and turbo anymore.

Same thing with the BMW but I have not put a catch can in, higher boost pressures push more oil through the PCV, it ends up going through the intake into the turbo.

You're right though, my choice of words was poor, I should have said they consume oil, not use it. It's not an engine problem with either or mine (or yours), it's just a design issue on the CCV.

 

[STx]

Interesting comment: I don't recall any of our 2, 4, or 6 cylinder diesel tractors using enough oil between changes to require adding any. This is on both naturally aspirated and turbo models. We changed oil approx every 100 hrs.

This on diesels made in the 50's through the 80's. Are new vehicles worse?

Think about this though, 100 hours in a car is probably only 3,000 miles unless you do a lot of highway driving. Most cars probably average only about 30MPH so on the current 5,000 - 10,000 mile oil change interval, that is recommended by most manufacturers now, you're talking 160 to 350 hours between changes.

In my case, my turbo diesel 7.3 also uses oil to run the injectors and has a crankcase vent that will bypass oil. The offender in the BMW is the CCV as well, and the higher my boost pressures, the more oil I lose. Neither is actually burning the oil.

 

[Copperhead]

That's the issue with both of mine, the crank case is vented back into the intake and because the crankcase is pressurized by the turbo, it'll push some oil through that vent. I removed that intake vent on the 7.3 (which also uses oil to drive the injectors) and vented it to atmosphere like International does with the big brother trucks using the same engine, it still consumes some oil but I don't have the carbon and gunk buildup in the intake and turbo anymore.

Same thing with the BMW but I have not put a catch can in, higher boost pressures push more oil through the PCV, it ends up going through the intake into the turbo.

You're right though, my choice of words was poor, I should have said they consume oil, not use it. It's not an engine problem with either or mine (or yours), it's just a design issue on the CCV.

It was not intended as a poke at your choice of words so much as it was getting to the heart of what is actually going on. I did similar to a 2006 Jeep Liberty Diesel. They had the CCV tube routed to just before the turbo and oil would get sucked up by the vacuum on that side when the turbo spooled up. I routed it to the ground just like my 2006 Cummins ISX was from the factory.

At least with the HD commercial engines now that they have gone to CCV since 2007, they are putting oil capture/filtration systems, or "catch cans", on their engines right from the factory. They saw this coming a long way off in testing and realized that they had to remove oil from the CCV to ensure proper operations and long term reliability. The auto / pickup OEM's, they always seem to be the ones who are dragging up the rear and it takes forever for them to get it right.

 

[clemsonfor]

just a few years ago GM considered normal oil consumption something like a quart in 500 or 600 miles

 

[CobyRupert]

I've let a dealer or someone else change my oil once in 30 years. It was when I bought my first new car, I took it in for the 5000 mile break-in service, thinking there's some mystery service and special tightening that has to be checked or done.
Never again. Luckily I park on cement, because the idiots didn't tighten the oil filter and I would of probably blown up the engine of my new car at about 5500 miles. And I'm sure they would of shrugged and said "Not our problem, the manual says to check oil at every fill up."
There's only one person I trust, myself, and some days I'm not too sure about him either!

 

[TCJatko]

Not to quibble either but 0.5 of a gallon would be 1/2 a gallon. 0.5% would be 1/200 of a gallon. 5.0% would be 1/20 of a gallon. Move the decimal in front of the 5 would add a zero.

Thanks for demonstrating your masterful grasp of the decimal point. The point I was making was that the poster identified one half quart as acceptable oil consumption based on the figures of 0.5 % per 100 gallons of fuel consumed. This ratio tells me that one half gallon, or two quarts, would be an acceptable oil consumption rate.

 

[Copperhead]

just a few years ago GM considered normal oil consumption something like a quart in 500 or 600 miles

In some cases, they still do.