(quoted from post at 18:10:42 01/13/22) I use it regularly in engines with lots of hours on them. If it does not have an emission system, the additives are perfect as they replace the moly, zinc, Phosphorous, and other additives that were removed when the catalytic converters came along, especially on HD diesel oil. These additives will actually attack a catalytic converter, coat it, thus rendering it useless. I also add some to gear boxes on shredders, balers and others when I service them. ON the gear boxes you usually see a reduction in heat. On the older engines, less blowby, and quieter in most/some cases and better running and less oil consumption. SO yes, it (lucas) does exactly what it says it does. Their hub oil for trailer bearing has saved me and others several times when a cap came off and running the bearings with no lube. SO again lucas hub oil is famous for floating axle bearings. So, yes I vouch for the lucas products in general.. Their power stg and seal conditioner will reduce, slow down, and in lots of cases stop a minor fluid leak. On new engines... with catalytic converters, NO I dont use it for that as it will probably damage the cat and dpf systems. I have tried the slick 50 and could never see a difference, so I dont have faith in that product. STP oil treatment (from the Studebaker Packard company) was designed to stop an high oil usage problem and yes, it will/does work. ymmv.