Thread: V8s on LPG - Flash Lube Required

Taxis don't use it, Ford dedicated LPG vehicles don't use it.

But, LPG comes out cold and dry without any lubricating additives, so the valve seats, stems and seals get no lubrication.

It can't hurt and may do some good, particularly for cars allowed to cool down overnight and only used for relatively short journeys. However it is a hassel having to fill the bottle.

Some European LPG conversions come with electronically controlled upper cylinder lube kits, especially on small engines, that cuts off the LPG when the oil runs out. Electronically controlled "Flashlube" kits are available in Australia which use LPG injector pulse width to control oil flow. I haven't fitted one yet, I programme LPG injection to run about 15% petrol use under load, seems to work so far.

The problem with modern engines is still seat wear, and as shim-adjusted valve clearance adjustment requires lots of labour very few people bother checking clearances until it's too late. A twin cam Camry may last 100,000km on gas without Flashlube but then the head is scrap metal.

Thanks - but do the D3/D4 V8s need it.

My 101 had it when I bought it but I removed it 3 years ago and not had any issues.

Cheers

Garry

After buying some, I've been told by many it is snake oil.
If you go ahead, Garry, PM me and I'll post you a couple of bottles.

You can also use the system and fill the bottle with diesel to do the same job, so as Mick says it's overpriced, but whether it's completely snake oil this who doesn't know..

Originally Posted by garrycol

...My 101 had it when I bought it but I removed it 3 years ago and not had any issues. ...

The issue is about longevity of the valve components, lack of lubrication is not going to be noticeable in the short term or even over three years if you are doing only about 20K per year. However the issue is will the valves fail prematurely after 100K instead of 200K and that's where the debate it, what is reasonable life and for some who change vehicles at the end of a lease they don't care for the additional hassel and cost.

The other issue is how often do you run on gas and how much on petrol. If the vehicle starts on petrol and you run it for a couple of minutes before switching to gas, then you may not need the upper cylinder lube at all.

Thanks Mick -not putting it back on my vehicle though.

Diana - I have been in various car clubs and this issue has come up a lot - the general rule is if the engine is designed to run on unleaded fuel without additives it will run on lpg without flash lube or something similar. As you indicated taxis have been running on it for years without additives and they do exceptionally high kms.

Garry

Generally for the rover v8 I say no as usually you will kill the head (gasket) for some other reason before you kill the valves

when you've got the head off for that job you inspect and then redo the valves if needed.

Ok there are two different engines being discussed here. Old OHV Rover V8's have self-adjusting hydraulic valve lifters, hard seats and questionable oil sealing on the valve stem seals. Hence they are not known for valve burning under most operating circs.

HOWEVER the new tech engines of the 21st century are mostly solid tappets with inserted shims. ANY wear in the seats and valves WILL result in hotter valve heads and power loss as the valves ride open for longer. If the engines are used predominately in a light duty scenario they will last a long time on LPG without extra lube. The problem in the UK is most likely that many of these engines spend a lot of time cruising motorways at high speeds, so they burn the valves quite easily. So proper application of upper cylinder lube will substantially increase the life of these engines. In Australia that means all newer aftermarket converted LPG vehicles used for towing and freeway travel should have some form of upper cylinder lube.

Fixing a burnt valve on a 3.5 is an afternoon's work and a couple of hundred dollars, fixing one on a twin OHC head is painful. I did a burnt valve on a customer's 3200 V6 Rodeo (and all the exhaust shims, 12 of them) and I can tell you, it wasn't a quick or cheap job.

I have yet to do a LR V8 of this era but there are tons of Jap engines that have valve problems if they are flogged on gas without lube. Not necessarily straight away but in some engines 20,000km, some 100,000km.

Toyota especially list in the handbooks of their vehicles that only engines designed for LPG should have it fitted. Camrys and Hiluxes can be dealer ordered to have special gas proof engines supplied or there will be no warranty for valve wear on LPG. Like the LPG Falcons they don't need lube if they are specially made for gas. Lube will allow non LPG engines to function to their design life.