Driving the Subaru Forester LPG

Introduction

Subaru has a new turbodiesel up its sleeve for 2008, but in the meantime it has launched liquid petroleum gas (LPG) versions of its popular Forester, Legacy and Outback models. Here we try the Forester SUV, which uses a conversion carried out by Millbrook, one of the leading LPG installers in the UK. What makes this conversion different from others that have been carried out on Subarus before is that it has a full three-year, 60,000 miles manufacturer-backed warranty. You can choose to have the conversion carried out before collecting your new Subaru or have the work carried out at a later date.

What is it?

The LPG conversion means ousting the spare wheel from its home in the boot floor. In its place is a large, circular tank that's referred to as a doughnut tank due to its shape. This doughnut tank is in addition to the usual petrol tank and is a very neat, uncluttered installation. When the boot carpet is placed back over the tank, there's no intrusion into the load space or any sign of what lurks beneath.

The only clues to the Forester using LPG are the discreet supplementary filler mounted just to the rear and below the normal petrol filler flap and the dash button to switch to LPG. Once the engine has been started as normal, the LPG fuel is used by pressing the button. There's a faint whirr from the doughnut tank's pump before it quietens down and, when the button's light goes from flashing to a constant light, you're running on LPG. The button also has a series of lights marking its circumference to tell you how much LPG is in the tank. You can switch between the normal petrol and LPG tanks at any speed, and with the combination of the two it usefully increases the Forester's journey range.

How does it drive?

Other than the initial whirr of the LPG tank's pump when it's engaged, you would never know that this car runs on the liquefied gas. There's no hassle to using it, no big drop in performance and the weight of a full tank is not much greater than the spare wheel it replaces, so handling remains unchanged.

The Forester LPG's 2.0-litre 'boxer' engine is, if anything, slightly more refined when using LPG than it is on unleaded. It's not quite as forceful when pulling hard to overtake slower traffic, but this is only noticeable when the engine is closing in on its red line, and you can always switch back to normal petrol power if you feel the need for those extra few horsepower.

The LPG-fuelled Forester is every bit as good to drive as any other. It has plenty of grip, direct steering and surprising agility for an SUV, although there's a fair degree of lean in bends. This is a pay-off for the supple ride that is ideally suited to the rural roads that most Foresters spend their lives negotiating. Standard four-wheel drive helps with on-road traction, but the Forester is not up to any serious off-roading.

Planet hugger or planet mugger?

Run a Forester only on LPG and you'll produce a shade less than one tonne of carbon dioxide emissions per annum, as well as fewer other harmful gases such as oxides of nitrogen. Using LPG, you can travel about three quarters of the distance possible on the same amount of unleaded, but the lower price of LPG makes it attractive. On top of the environmental savings, those living in London and proposed congestion charge zones are exempt as LPG is seen as clean and green. Even with upcoming changes to the London Congestion Charge, the Forester LPG would pay less than a petrol-only version.

Verdict

LPG is a balancing act between the cost of the conversion and the savings it gives due to the significantly lower fuel costs. At present, LPG costs around half that of unleaded petrol, so for someone travelling 12,000 miles or more per year, the Forester LPG pays off its £1,918 premium over a standard Forester in just less than three years. LPG is better for the environment than petrol and you can run a Forester solely on LPG with this conversion, so it's a muted thumbs up.