There's an affordable new BMW 5-Series on the block - an entry-level turbo diesel with all the advantages of this refined premium saloon at an attractive price. It's still not cheap, but at £25,925 there's no denying the appeal of this "budget" 5-Series.The six-speed manual gearbox fitted to my new 520d was slick enough, but it wouldn't be my transmission of choice and that immediately makes the entry-level car nearly £1500 more expensive. Well-spaced ratios and a light action make the manual box easy to use, but if the 520d was on my shopping list I'd spend the extra £1450 and bag myself a six-speed Steptronic automatic. It's one of the smoothest-changing auto systems on the market and makes driving the 5-Series a relaxing affair.But my 520d test car was manually cogged - a transmission which takes full advantage of the two-litre turbo diesel's quite astonishing economy potential. Compared to the automatic 520d the manual manages to average an additional seven miles for every gallon. That's an amazing differential. What's more, on the extra urban cycle the automatic's quite respectable 51.4mpg looks downright excessive set against the manual 520d's frugal 61.1mpg.It underlines the efficiency of the 163bhp engine and the manual gearbox. On gently populated urban roads and open countryside I was astonished to see the on-board computer average 54.3mpg - achieved with a fair amount of cruising at the legal limit and a lot of brisk overtaking. Driving hard, I still managed 43mpg.It should have come as no surprise. This engine is already used in the new 3-Series and X3. It's very smooth, delivers exceptional pulling power and runs cleanly with an exhaust emission level of just 158g/km. That adds up to good news for company drivers looking to lower tax bills and private owners keen to stretch every gallon of Derv as far as possible.Performance is adequate rather than dynamic. The 163bhp is fully developed at 4000rpm while peak torque of 250lb/ft arrives at 2000rpm. Acceleration from rest is a leisurely affair with 62mph coming up in just under nine seconds while the vital overtaking slot between 50mph and 75mph is covered in an impressive seven seconds in fourth. At no time did the modest 520d feel underpowered - but this is no BMW fireball.Top speed looks good on paper at 139mph. In reality it means the car is good for a comfortable 100mph and very laid back at the legal motorway limit with only intrusive tyre roar invading the well-insulated cabin. Engine noise is perfectly suppressed. Even at tickover the turbodiesel produces little more than a soft compression ignition knock while throttle pick-up is impressively quick and clean.Like all 5-Series models this one gets DSC+, the latest version of BMW's excellent dynamic stability control system. It makes the most of the car's outstanding chassis, lightweight suspension and powerful braking.Not only does it deliver advanced traction and cornering control but DSC+ delivers Hill Start Assist, Brake Standby to reduce emergency braking times, Rain Brake Support to keep discs dry, Fading Compensation to maximise stopping power even when the brakes are hot and Soft Stop to ensure all stops are jerk-free and smooth.Of all these features the most practical on the manual 520d is Hill Start Assist. It allows the car to be driven away on a steep hill without the risk of the car running backwards in those embarrassing milliseconds between letting off the handbrake and getting the clutch to bite. It's a small point but, like the Soft Stop programme, it helps smooth the driving experience for whoever is at the wheel and his or her passengers.It may be at the bottom of the 5-Series turbo diesel food chain, but the 520d is no bargain-basement special. This is a refined and comfortable five-seat executive saloon which carries all of the quality of its more expensive sisters. It has the same steel and aluminium composite body construction as the rest of the family which means a strong and lightweight body.That in turn makes the modestly-powered 520d feel agile. Front suspension arms, the front chassis legs and the bonnet are aluminium. It's the same story at the back where the superb four-link arrangement carrying the driving wheels also uses weight-saving alloy.On a cross-country route I found very little difference in journey times between the 520d and the mighty 550i. The simple fact is that the 520d is quick enough for Britain's congested roads. It may not have the cache of a 550i, but then again it does not cost the mighty five-litre V8's £43,550. The 520d is very much the "junior rank" 5 but it's an impressive car for the price and likely to become many a fleet manager's best prestige friend.Second opinon: If you're looking for excitement from a BMW, search elsewhere. This is not an especially interesting car, at least compared with other models in the 5-Series range, and in particular the phrase "The Ultimate Driving Machine" seems heavily ironic here. But it's efficient, it attracts attention (even if the colour scheme didn't endear the test car to friends and neighbours) and of course it has the cachet of the BMW badge - all of which will probably be enough to entice a good many potential buyers. David Finlay. Engine 1995 cc, 4 cylinders Power 163 bhp @4000 rpm Torque 251 ib/ft @2000 rpm Transmission 6 speed manual Fuel/CO2 47.9 mpg / 158 g/km Acceleration 0-62mph: 8.6sec Top speed 139 mph Price From £25196.00 approx Release date 12/09/2005