How to read my odometer???

snowwy, it is a common misconception that it happens at idle but it doesn't. Blowby is a measurement to see what the crankcase pressure at a full load at or near peak torque, I think cat engine are high, 21 inches of water, but I could be wrong, I have only a few cats in my life.

What happens with idle is the venting of moisture through heat and vapor.

 

Undersized pistons is a thing with cat.

Heat and vapor don't smell like exhuast. And that would have to be some serious vapor in the summer time.

There isn't an engine in the world that doesn't have blowby. NO engine has perfect compression. But good engines keep it down to a minimum in that it's not seen with the naked eye. Cat engines aren't the greatest in that aspect.

I know of one cat engine. That got brand new pistons at 150k miles. All 6 rings were broken. My liver was not a happy camper driving that truck that summer.

 

Yup. On any motor. Used to be, before buying a truck, we'd start the motor, crawl up under it, put our hand over the blowby tube, see how much oil was coming out.

 

Not all 15 year old trucks have a million miles. Some are used locally, others, very locally...BUT...they might have a ton of hours on them from idle or running a PTO. I used to run a local route in a day cab, if I went 500-700 mi a week, that was a lot. Some weeks only a few hundred miles. But, motor was typically ON from the time I started in the early AM until I shut it down when I got back to the yard. Of course, this was long ago before anyone really cared about emissions.

 

You're right but I think if it was a 15 year old truck with low mileage it would be part of the selling point. Opinion of course.

 

Right, or so you'd think!!!

But, if it isn't the owner who is selling it, the story get's "lost".

Hence, I try to stick with buying things directly from the owner versus a dealer. But, I can see how that has it's limits.

Again, I look at what the ECM says as well as the number of hours too.