The older the better imo

I tend to agree with that sentiment about Volvo`s too.

I have a 97 850 T5. Been on LPG for about 5 years now, with no flash lube and no problems.

Good result at the weekend. Car past the MOT without any work required...2 years on the trot now and I found an LPG supplier nearby selling at 70p per litre

I've been running on lpg for 4 years, the car much longer. I've just stripped the head and the valve seats are fine. The valves are bent unfortunely due to a idler pulley failure. No valve lube ever fitted and the oil was always clean after thousands of miles.

If worried about the dryness of LPG causing damage to valves....

Wouldn't it be simplest to always put a hefty shot of Redex or similar in the petrol tank with every petrol top-up? You're guaranteed a few minutes running on petrol every drive and could always switch back for a minute or two every few hundred miles on the motorway to lube up the top-end..

Seems it would be a lot simpler than having the flashlube equipment and buying the special additive for it. Although the jury seems to be out as to whether anyone with an old style Volvo even needs it...

Redex does nothing and I'm fairly sure it will not even help a car that needed 4 star run on unleaded. Has redex been aproved as yet for that?

The jury is not out there on what older volvo's need any form of valve saver. The only question mark engines are pre B21. The B14's and then engines after 2005.

In a na engine the flashlube is a very easy system to use and is uncomplicated.

It might do ! Even the factory Bi-Fuel heads had a recall for valve seat recession around 2001-3

I guess a more useful question is to what extent the valve seats are likely to recede in a 2001 car.

If I go for an LPG conversion I'll be expecting a 5 year life and 80K to 100K mile lifespan (Car currently has 83K after 11 years use - I buy cars with an expectation of them lasting to between 150 and 200K and I do about 20K a year)

Doesn't matter if the seats recede as long as this doesn't become a serious issue in my intended usage lifespan. If it's a problem that begins fast and wears away enough of the material to degrade performance, I need to worry, buy flashlube, or not convert. If it's a fractional thing that will be undetectable before the car's too old to be worth maintaining anyway, then I'll not worry, and have a lube-less conversion instead...

And if I can prevent recession just by running on petrol for a few minutes every hour of engine life.. then thats probably even cheaper than flashlube, might even design a timer circuit to make it automatically switch for 5 minutes of every hour when running on autogas.

when volvo had the problem 10 years ago it manifested itself by valve clearances closing up and the mileage was over about 50000 miles .

regarding the B14 above . No problem , volvo fitted better valves than Renault and my 343 did well over 100,000 miles on LPG from 1983 to 1990 with no valve issue at all .

The cause of this will be down to the factory fit system itself causing lean out. It is the lean burning that results in the reduced valve temps causing the damage. A better quality system that is capable of acuratly contoling the fuel dosage will not get the issues.

Even so 50000 miles before any problems arise is not bad going considering the system used.

I do not fit the flashlube as standard but will do if a customer wants some insurance. Squirting in petrol in small doses will be a lot more expensive and more hassle than fitting a valve saver kit and keeping it topped up.