Petrol and diesel go head-to-head

  • We find out if new petrol engines are good enough to usurp diesels.
  • Fuel and tax costs combined to find out which costs you more
  • The biggest players in the company car market go head-to-head

Diesel is the traditional choice for most company car drivers - and those private motorists that do large mileages - for good reason. Generally cleaner when it comes to CO2 emissions and offering higher fuel economy, the diesel engine has historically worked out the most savvy choice for company car drivers and fleet managers.  

The latest wave of petrol engines are more efficient than ever though, and with diesel now costing around 10p more per litre, now seems like the perfect time to ask whether petrol is about to make a comeback.

We take a look at petrol and diesel engine choices for the popular choices in the company car market to find out if diesel is still king, or whether it's been overthrown by it’s second in command.

Ford Fiesta

The Fiesta has been the top selling car for many years, both for retail buyers and company car users and is available with a wide range of petrol and diesel engines.

It's the award-winning 1.0-litre EcoBoost that carries the flag for petrol power, and we've put it up against the uber-frugal 1.6-litre TDCi ECOnetic.

We have chosen both cars in five-door  Zetec trim as it offers a good balance between equipment levels and price. Standard kit includes air conditioning, USB connection, heated windscreen, Ford’s ‘MyKey’ technology, interior leather trim details and electric mirrors and windows.

  Petrol Diesel
  1.0-litre EcoBoost 1.6 TDCi ECOnetic
P11D £14,440 £15,840
MPG (Official combined figure) 65.7mpg 85.6mpg
CO2 emissions 99g/km 87g/km
Power 98bhp 93bhp
BIK tax band (2014/15 tax year) 12 14
Monthly tax costs* £28.88 £36.96

And the winner is: Diesel

Based on you travelling 1000 miles over the month, your fuel and tax costs combined would cost £118.56 monthly for the petrol and £106.45 for the diesel – close, but the Diesel Fiesta still triumphs.** 

Volkswagen Golf

The Volkswagen Golf is the failsafe choice as a company car with solid performance, all-round versatility and a proven track record for reliability.

There are a choice of five petrol engines in the entry-level S trim to choose from, but lowly standard equipment lists mean a move to SE is a must. At this level only the 1.4TSI with BlueMotion Tech is available. Best get a DSG automatic gearbox too as it increases efficiency, lowering tax bills.

Bluemotion technology features on the 1.6TDI diesel engine too, and in full-fat (or ultra skinny latte, depending on how you look at it) Bluemotion trim, the Golf sets new benchmarks for CO2 emissions and economy. You'll find manual air conditioning, 15-inch alloy wheels, Bluetooth, 5.8-inch touchscreen system, stop/start technology, variable boot floor and a centre armrest all fitted as standard.

The petrol SE carries all of the above with the addition of cruise control, 16-inch alloy wheels, leather interior touches and a driver profile system which has five different modes the driver can select; Eco, Sport, Comfort, Individual and Normal.

  Petrol Diesel
  1.4TSI BlueMotion Tech DSG SE 1.6 TDI BlueMotion
P11D £21,495 £21,295
MPG (Official combined figure) 56.5mpg 88.3mpg
CO2 emissions 116g/km 85g/km
Power 120bhp 103bhp
BIK tax band (2014/15 tax year) 16 14
Monthly tax costs* £57.32 £49.69

And the winner is: Diesel

Based on you travelling 1000 miles over the month, fuel and tax costs combined are £161.60 monthly for the petrol and £140.22 for the diesel – quite a big margin on costs here, even when you consider the extra kit on the SE trim. **

Audi A3 Sportback

The launch of a new 1.4TSI petrol engine with Audi’s new Cylinder on Demand technology has thrown a bit of a spanner in the works when it comes to the A3 Sportback.

Although diesel would be the traditional choice for company car drivers, this  petrol engine has some impressive credentials; there's more power on offer than the equivalent diesel and competitive mpg and CO2 emission figures. Opting Again for the S-Tronic gearbox sees these emissions reduced further.

When it comes to kit the SE trim has more than enough standard equipment available to suit most company car drivers with DAB Radio, Bluetooth, manual air conditioning, 16-inch alloy wheels, cruise control, stop/start technology, USB connection, eight speakers, and leather interior touches available as standard.

  Petrol Diesel
  1.4 TSI S-tronic SE 1.6 TDI SE
P11D £22,475 £21,095
MPG (Official combined figure) 58.9mpg 74mpg
CO2 emissions 109g/km 99g/km
Power 138bhp 103bhp
BIK tax band (2014/15 tax year) 14 15
Monthly tax costs* £52.44 £52.73

And the winner is: Diesel

Based on you travelling 1000 miles a month, your fuel and tax costs combined would cost £152.47 for the petrol and £136.89 for the diesel.**

However although the petrol is more expensive the extra power the 1.4TSI engine offers may make it worth the extra cash.

BMW 5 Series

Opting for a petrol engine is actually around £1000 more expensive then the diesel alternative. Against the grain perhaps, but this is mainly down to the diesel option needing to be keenly priced as it has far more competition.

There are two diesel choices here and both are evenly matched for mpg and CO2 emissions - only power and P11d price separate the 518d and 520d.  

For some company car drivers, the BMW 5 Series has been left out of reach but the lower powered 518d now starts at less than £30,000. Perfect for those with a lower company car allowance.  

But the 520d has 40bhp more and in tax costs, the 520d will only add around £5 per month for a 20 percent tax payer.

The SE trim, despite being entry-level, actually comes very well equipped with 17-inch alloy wheels, electric parking brake, cruise control, front and rear parking sensors, leather upholstery, automatic air conditioning, Bluetooth, seven-inch colour display with iDrive and a trip computer all available as standard.

  Petrol Diesel
  520i SE Saloon 520d SE Saloon
P11D £32,805 £31,910
MPG (Official combined figure) 44.1mpg 62.8mpg
CO2 emissions 149g/km 119g/km
Power 181bhp 181bhp
BIK tax band (2014/15 tax year) 22 19
Monthly tax costs* £120.29 £101.04

And the winner is: Diesel

Based on travelling 1000 miles a month, your fuel and tax costs combined would cost £254.02 for the petrol and £200.21 for the diesel.**

The petrol was always on the back foot in this case thanks to the higher list price, but regardless of this the £50 saving in tax costs is significant.  


There is no doubt that the gap between petrol and diesel engines is narrowing, and for retail buyers the lower list price can often tip the decision in favour of the petrol models.

For company users the tables are turned though, and with tax bills and fuel costs to think about, diesel is still undisputedly on top. 

*Monthly tax costs are based on a 20 percent tax payer

** Based on the official consumption figures and current petrol and diesel prices from the 17th Feb 2014