Pretty much I don't want to repeat the great advice already given about what to look for and do on these.
As a note, I only use premium. With that said, my friend has had his 01 Disco since new, and has always used regular. No problems or issues at all with it, and his economy is just fine with it. As long as there is no knock or ping with the lower grade, you should be good. Again though, I use premium and would offer the same advice to use it as well.
As far as the price, if it is a straight truck with nice options and clean record, yes, it is good. If the big service items like the head gasket were done, it is a great price.

 

its roughly $5 more to fillup our rigs with premium. if you cant swing 5 bucks per fill then you are driving the wrong vehicle

 

I agree with sloppyjoe, on average its 20 cents a gallon difference between low grade and premium fuels, so if you are talking about putting 25 gallons in, its just a 5 dollar piece of mind. Personally I have used all different grades in mine, and I seem to no changes in performance or mpg, but I still try to use premium whenever possible

 

Because the owners manual says so.

 

 

Except for the part where is says to use at least 91 RON, which is 89 octane.

 

As does the inside of the fuel door

 

I definitely notice the difference when going up hills on the highway. With Premium, ill be able to go up hills in my normal commute in 4th gear / Overdrive. With regular, its more difficult and the car will downshift to 3rd on the same hill.

Sometimes I'll alternate...

I'll fill up Shell V-Power 93
At half tank ill Fill Regular + 1-2oz Lucas Fuel Upper Cylinder Treatment
on next half tank, go back to V-Power 93

Don't wait till the gas light to fill since it can be bad for your fuel pump.

 

87 octane also burns at a higher temp than 91. And these truck engines do not like heat.....

That's my main reason if anything else.