I spotted this cheap Porsche Boxster with LPG conversion (LPG: liquid petroleum gas) on one of my regular valuation trawls through the classifieds last night. Even if you take the conversion off and run it on petrol, it’s still a Boxster for less than £2,500. This made it worth a little look.
First registered on April 26, 1999, this 986 Porsche Boxster 2.5 manual was supplied in Arctic Silver with Boxster Red leather trim. The combination is quite common on 986 Boxsters: Arctic Silver was available on all model years, while the Boxster Red option was a popular choice with the Silver. It has covered 144k miles and allegedly comes with a lot of history.
Online MOT history for T747 LYB shows that the mileage in 2005 was a mere 51,280 miles. In the twelve months that followed, that total leapt to 70,449 miles overall. It did another 9k in 2006, then 10k more in 2007. Here the MOT bills started getting expensive, with worn brakes, suspension, headlamp issues and emission flags amongst other bits. Pretty normal for the model and mileage.
The annual mileage then drops: presumably due to a change of keeper after that pricey MOT. 1k, 1k, 6k, 4k a year and more flags for brake pipes and brake force, until it crosses 100k miles at the July 2012 MOT. Then the mileage picks up again: 2014-’15 shows 9k, 2015-’16 is 12k, 2016-’17 7k and from then to now is circa 10k in total, taking it to a current mileage of 144,000.
Boxster friends report an average of 26-27 mpg (imperial gallon) for a 2.5-litre 986 Boxster and my local Shell station charges £1.35 a litre for V-Power. At that price, 10k miles in a 26mpg Boxster works out to £2,357. 144,000 miles like this works out to just under £34,000. £34,000 pounds spent on fuel with 66% of that price being tax: that is £22,440 fuel tax in this example! Ridiculous.
What’s the point of converting a car to LPG?
LPG is most commonly used in the UK to cut fuel costs and to create fewer emissions, thus reducing one’s carbon footprint. I have run an LPG-powered car for these reasons ever since switching from diesel in 2007 and would not run anything else day-to-day, so it is always interesting to see what cars other people choose to fit LPG systems to.
A Porsche Boxster is not the most obvious choice for an LPG conversion, but I have seen many converted to gas. As a long-distance solo commuter, it makes sense. The cars are fun to drive, but Porsche’s 2.5-litre flat-six engine is not the cheapest to run, even when it doesn’t let go. LPG as duty paid road fuel can be half the cost of petrol in the UK, meaning that your fuel costs are effectively halved overnight. All good so far.
LPG burns with less of a bang so you lose a bit in MPG, but the difference in performance is barely noticeable. The only real downside of an LPG conversion is having to fit a second fuel tank, and a heavy one at that. LPG tanks are several times heavier than petrol tanks due to crash regulations. If you have a spare wheel well for a toroidal tank to drop into, it’s not so bad space-wise, but the weight would be noticed on a Boxster. The tank weight’s not that obvious on my 4×4 daily drivers.
A typical installation on a car like the Boxster would involve tank and filler, supply pipes, evaporator and injectors. The ECU piggybacks onto the car’s ECU and no changes are required there. Cost would be something like £1000-£1200, so you have to earn that back through fuel cost savings before the real fuel savings kick in.
LPG fuel savings calculated
My previous daily driver Cayenne S V8 cost £1300 to convert and went from 17mpg average on petrol to 15mpg on LPG. My current daily driver – a 2006 Honda CR-V – cost £800 to convert and went from 26mpg on petrol to 24mpg on gas. Fuel costs for both come down from V-Power at circa £1.34 a litre to LPG at 68p a litre. While the mpg fell by about 8%, the fuel cost dropped almost 50%.
Benchmarking fuel costs per 1000 miles, the CR-V costs £235 to do this on petrol and £128 on LPG. So every 1000 miles saves me £107. The £800 conversion cost divided by £107 saved per 1000 miles is 7.47, so I earned my conversion cost back after 7470 miles (about 6 months or so) and am now into savings. I ran my Cayenne on LPG for almost 50k miles: that works out to saving approximately £6500 in fuel (i.e. over £4k in fuel tax) at current prices when the cost of the conversion is taken off. Plus I got to drive a petrol V8 with lower emissions for 50k miles.
This Boxster is already converted and has reaped similar fuel savings benefits: a substantial sum of money if it was converted early in life. As with any Boxster, high or low mileage, this car would need careful checking before a purchase, but the main thing to check would be the engine and gearbox. LPG does not lubricate and cool valve seats, so the fuel can cause valve seat recession if the head material is not hard enough. My LPG man flagged this as an issue on Porsche, so the gas should have been run with a valve saver lubricant to compensate. If this has not been done, or the owners were lazy about keeping it topped up, it will be uneconomical to repair.
Porsche Boxster buying notes
Now more than twenty years old, the fuss-free styling of the first Porsche Boxsters have made them true modern classics. Collector preference is always for low mileage and the lowest mile non-S in the UK is a 2001 2.7 car in Guards Red with a mere 22k miles for just under £9k from a dealer in Scotland. Perhaps a little rich given what else is available at the same price point, but you don’t have to spend nine grand to find a nice example. The effortless chic of a simple early Boxster can be bought for less than £5k.
All low-priced Boxsters come with a job list and it is often more cost effective to buy an expensive car in good order than a cheap car needing tidying. The bodywork on this one looks a little patchy and the leather is tired with a hole in the driver’s seat bolster, but it has the hardtop and is MOT’d until June 2019. It would probably break for spares fairly easy if it fails its MOT big time. An asking price of less than £2500 is certainly interesting to those of who like cheap Porsche projects.
Caveat emptor and let me know if you buy it. Check that engine and then check it again! Visit my website at porschevaluations.com to get an agreed insurance valuation for your classic Porsche Boxster.
Porsche Boxster for sale ad text:
1999 (T) PORSCHE BOXSTER 2.5 PETROL/GAS
144,000 miles with loads of service history receipts etc.
M.O.T TILL 8th JUNE 2019
Starts and drives great with no issues. Well maintained example, bodywork is great, also interior is very clean and has just been fully valeted ready to go.
Alloy wheels, CD player, remote key locking, air conditioning, full leather seats, onboard computer and much more
ANY TRIAL OR INSPECTION WELCOME