There are a couple of stops in the Ventura area. There is a USA on Central Ave, very close to the 101. I've never used it but I see diesel trucks, not just pick ups, and MHs in there. About 1/4 mile from the fwy. It's close to Ventura Harley which you can see from the 101 fwy.
On Del Norte there is Macvalley Oil, corner of Sturgis and Del Norte, regular truck stop, scales, snack bar and also an adjoining station. Del Norte is about 1 mile west of the Central Ave offramp, go south on Del Norte about 1 mile.
There is also a truck stop CFN station, it takes regular cards too, on Ventura Blvd between Victoria and Johnson Dr, you can see it from the fwy going west/north. It's not real convenient to get to I would say that the Johnson offramp would be your best bet. Exit and go under fwy and back around behind Toys R Us. Kind of a PITA but big rigs make it. Victoria is pretty congested, but it will take you there also.
On Vineyard Ave there is Pinto Petroleum (I think) about 3 miles north of the 101. It's a card lock and I'm not 100% sure about regular credit cards. It is easy in and out.
Please try to verify these on line, I'm going from memory, I see the places almost daily, but I never pay much attention. I can't think of any in Thousand Oaks, Newberry Park or Agoura. I fuel up in Santa Paula off the 126, convenient for me but way out of your way.
Terry