Correct engine oil for my car

I own a 2003 Volkwagen Golf Mk4 1.9 TDi estate with a PD diesel engine. Although I have never done oil changes myself, I do know that it is on a longlife service schedule, and I am pretty sure it has...

How expensive is an oil change?

A garage charged me £112 for engine oil for a Toyota Hilux oil change. Would this be right as it seems very expensive oil?

What engine oil should I use in my 1980s Polo?

What engine oil would you recommend for a 1988 VW Polo, 1.3 litre, which has done less than 20,000 miles in 36 years, with regular use (I.e it has not been standing unused). The handbook, now 36 years...