I've been driving my truck with a broken (solid on) clutch fan for about 4 years. It made the A/C work much better in town, so I never worried about it.

Finally got around to replace it and my mileage went from 14.4 (avg town and highway) to 16.6.

I had no idea it would make that big of a difference.

I'm a little worried about the upcoming summer, but I'll take the bump in MPG.

 

My 1993 5.0 had a heck of a time staying within normal temp range. My OEM fan clutch wore out and I replaced it with a parts store brand clutch. It either didn't work well or wore out too (been too long to remember).
I gave up on a clutch and installed a spacer for the summer moths (direct drive fan at this point). That thing would sure howl but it helped with cooling.

No doubt it cost money to run based on the amount of noise and performance loss. Ever driving a 5,000 lb truck up a hill with a motor making about 170 hp with a locked up fan clutch. I was mistaken for an airplane that takes off from the airport at the top of the hill. LOL

You gained 2mpg -I bet the old truck of mine got at least 5 given how powerful the trucks are now compare to the slug I used to drive.