30 to 50 a week that an awful lot how are you figuring that?
Wild guess, gotta be. Saving $30-$50 a week would translate into buying $1500-$2500 in fuel every week for highway miles. It's more like $25-$35 a month.
Air Tabs are $2.75 each (were $2.50 each at the time I got mine). The bigger the vehicle the more you'll need, but the fuel savings percentages are more or less consistent across vehicle types if you install the recommended number at the recommended intervals (3 per linear foot, or every 4 inches on center). The fuel savings is between 2% and 5% depending on how fast you drive and the vehicle. A Sprinter or cargo van (without a right-angle, boxy rear end) will see closer to the 2% while a boxy truck will realize more drag reduction and will see 3%-4%, while a tractor-trailer with Air Tabs on both the tractor and the trailer will see that 5% savings.
I've got 30 on my Sprinter, that's $82.50 ($75 when I got mine). It took just about 4 months for that initial investment to be recovered in fuel savings. If you spend $100 on fuel, the Air Tabs will save you about two bucks on that fuel, give or take. So it's not an
"OMG look how much fuel I'm saving!" kinda thing. But it adds up over time.
The first 4 months I had them it was a wash since they were paying for themselves. The 72 months since then have saved me about $25 a month.