Your credit report history is on your ability to make payments (preferably on time), it will not be affected (Positively or negatively) by repaying a loan early
Your "Adverse" credit history is what most lenders/banks/finance houses are interested in (late/missed payments, Mortgage arrears, CCJ's for council tax, household bills etc), using your CC to pay for Fuel each month is a good way of gaining regular payment credit history, simply put if you use it to pay for fuel and pay off each month is shows regular payments for credit history however on the flip side it means that your bank is less inclined to increase your lending as they don't make money from you and technically you don't need it
If your concerned with your credit report you can request a copy of it from Equifax or other companies, I did it several years ago and found 2 "Missed payments", one from Orange Mobile and one from Vodaphone, called them both about it and it was their error (as usual) as they forgot that my contract had ended and both were removed.