John I picked up a gallon of Archoil AR9100 last fall as well as a quart of Archoil AR6200 gas/diesel fuel additive.
We have two old 60 HP diesel engines (310B John Deere backhoe and 265 Massey Ferguson tractor) and many old gas vehicles.
The AR9100 by the gallon with shipping was
The 1989 F700 truck with the Lima 429 four barrel is the one engine I have notice a subjective positive change. It was showing 144K miles when we got it with NO history and very dirty oil and a NAPA Gold oil filter in 2010. We changed it out with Rotella 5W-40 and a new Wix's oil filter and the oil was black after one 200 mile round trip so we started doing Filter Only changes. After the third filter the Rotella T6 stayed relative clear for the 1000 miles it was in the crankcase when we changed it again in late 2014.
We had the the wooden bed floor replaced with 3/16" steel and built a temporary grain box inside of the 2' dirt/gravel sides so I could help my brother when he got in a bind shelling his corn and put 1000 miles on it going to the grain elevator 10 miles away.
Those were hard miles because one the first load my brother filled it completely which was a serious overload of 24,000 pounds of corn on a truck that is rated at 23,100 pounds and weights 13,000 empty.
The one thing that I noticed after a few hundred miles of working it very hard with a lot of WOT time is the old 429 would spin much faster when engaging the starter. This does not really make much sense to me unless the old big block had a lot of friction that the .037 friction modifier reduced.
A couple weeks ago we picked up a 2007 Dakota truck for the daughter that had 62K miles. The owner for the past 30K miles said mainly she drove it 8 miles to work. The Chevy dealership had changed the oil and used a 10W-30 GM oil they reported. It was very thick and almost black in color. I added the AR9100 to the crankcase but with single digit temps coming and the new oil black I had it changed out with Motorcraft 5W-20 after running the AR9100 for only 60 miles. I did add and run it the last 20 miles (trip to town to get the oil changed) with 8 oz of SeaFoam added to the crank case.
After 200 miles on the fresh oil change with the Archoil AR9100 added the oil is still relative clear but until when it set for a couple months on the dealer lot the min trip is now 30 miles if it moves. We have been snowed in for a week now and it has stayed parked since it is the newest thing on the place and bright white in color.
At just under $2 an ounce I plan to use Archoil AR9100 as a full time crankcase cleaner and oil friction modifier in every four cycle gas/diesel engine that we own. You use 1.12 oz per quart of engine oil capacity. We have engines that may set years without starting is also a factor in my decision to use Archoil products.