Well I don't want to stir the fire to much but I found this online about different air filter tests and thought it'd be worth sharing.

End results of these tests were (worst to best); Jackson Racing, Amsoil, K&N, Mazda, Baldwin, and Napa




They also had a neat thing about using additives like Lucas as well, it can be found here.

 

Interesting but very unscientific.
To do it right the particles on the second test filter would have to be analyzed. My bet is the darkening on the test filter is just oil residue that collected in the first few miles after the filter was serviced since the oil type filters are showing the darkest. Bet if he would have used a new test filter after a couple hundred miles that there would be very little visual difference between test filters.

 

Quick comment on the Lucas site. I added a quart of Lucas additive a couple of years ago along with a fluid change to the 95 as the 5 spd was making a small amount of noise (110,000 miles), thought what the heck can't hurt. And it did quiten it down.

Well, a few weeks after adding it I visited the site listed above saw the Lucas demo and thought, gotta change the fluid again.

However I decided to do a little test, one day after pulling the backhoe 20 miles or so working the truck fairly hard, I immidiately drained a sample of the transmission oil into a glass container. No, as in Zero discoloration or evidence of air.

At about 150k, when changing clutchs, I sent the tranny to Standard for the fully splined mainshaft upgrade (never lost 5th just preventative) and had them return all the old parts. To the naked eye, all bearings and wear items looked fine.

So, when we bought the wifes truck with a noisy 4500, along with a change of Syntork, I added a quart of Lucas.

No ax to grind, just my observations.

Good luck, RJR

 

He claims it wasn't oil but like you said it wasn't very scientific, so I'm sure there is no way of knowing by just looking at it.

The speed caused the foaming rather than stress, I'm not saying one way or another but you put stress on it by pulling a backhoe. I sure hope you weren't testing speed too.