I add a quart every oil change it's recommended for daily use it has more tack to it then normal motor oil it also helps prevent dry starts, also don't be alarmed when your engine sounds like a blender full of rocks for the first 5-10 seconds when you first start it back up it's because you have stripped all the oil from the engine with the flush and you put on a new oil filter which you can pre-fill a little if installation will allow, but it will quiet up in a few seconds and sound great when your done. Also make sure you follow the directions to a "T" add to a cold engine, don't rev the engine or drive it and only run 5min then drain and replace the filter (make sure you get the 5min flush as it's more aggressive it's in a grey bottle made by Gunk brand) also they don't mention it but I buy an extra quart of oil and just before filling it back up I pour the extra quart in and let it run out you will see it go from black to new once that's done draining pull off the old filter and install the new one and the oil plug and top up with lucas and a slightly heavier oil then it specs for since it's high mileage i guess it calls for 5-30 that's why I would say go with 10-30.