Hertz Hire Car Charges For Full Tank?

We're flying with Ryanair to Zaragoza this year and we want to hire a car with them...ie: with Hertz.  They say we have to pay for a full tank of fuel (I assume this will be when we arrive to collect the car as it isn't included with the price given) and they say this will be at the price of fuel at the time.  We've read the stories about being overcharged for fuel through this type of scheme.  Has anyone used Hertz through Ryan Air? Are their full tank of fuel charges reasonable? 

We were going to take our own car on Brittany Ferries but the cost of the ferry works out at over £200 more than flying with Ryan Air and hiring a car for two weeks!

Hired a Hertz car on Friday, the tank was full and we were advised to return it full which we did. My experience is that if you don't return it full you not only pay higher prices for the fuel but also a fee for them having to do it. If you have paid for a full tank in advance or on collection then you usually return it empty but that deal is not usual with Hertz.

This topic has been discussed in some detail on a previous thread.

My experience has been in recent years that it is very difficult  to hire a car on a full/full basis unless the hire is 3 days or less.

In the small print you will usually find a full tank of fuel always includes a admin charge.

For example my last hire for a 1.2 litre engine car, the fuel cost was Euros 77.85 + 21% VAT. In reality if you tried to put this much fuel into the tank it would overflow !!

If Hertz are offering a full/full option this must be one of very few.