karl from idaho, While I admire your scientific mind set, rememeber we do have a "before" sample already here. The oil right out of the jug is the "before" or zero data point already. Plenty of analysis data already on the "before" if you consisder the zero data point as the "before". But I say "go for it"! I am interested in your 500 mile sample data point. Hey! why not every 500? Expensive I know but it's your money I'm spending so I say "go for it all" man!!! Always makes a better graph to get more data points!