FOAK: Valve Seat Additives - Snake Oil?

I've been reading up on this a bit having bought an LPG car, & I'm none
the wiser. Some say you should always fit an automatic additive adder
with LPG even if it's a modern car designed for lead-free petrol, as
LPG burns much drier & has none of the additives used in unleaded.

Others say any additives designed to protect valve seats are pure snake
oil, & were just invented to fleece the gullible when leaded petrol
started to disappear.

The system usually used with LPG is called Flashlube, & is basically a
Scottoiler that dribbles in 1ml of their special fluid for every 1
litre of petrol. Needless to say the fluid is hiddeously expensive -
around 20 quid / litre with postage.

There's lots of dodgy terms around like 'lubricating the valve seats',
which has led to some people recommending 2-stroke oil or ATF instead.
The mind boggles. What there doesn't seem to be are any tests comparing
identical cars with & without Flashlube. There are however stories of
people stripping their heads after a few hundred miles of Flashlube use
& finding the valve stems badly coked up.

On balance, I'm tending towards the snake oil camp, especially as none
of the manufacturers who offer a bi-fuel option fit Flashlube kits to
them afaik.

So I guess the question is, what are the chances of an aftermarket
additive doing anything to protect valve seats, & would it even be
needed on a modern engine with hardened seats?

 

As a top manufacturer recommends it for SOME vehicles it probably isn't
snake oil.
1L per 16k doesn't seem excessive?

 

I happen to have the Ford factory service manual for the CNG
(Compressed Natural Gas) version of the Crown Victoria, and as
far as I know there isn't any such system on those cars. I
suppose the valves and seats could be made of unobtanium, but
my guess is they are identical to those in the petrol 4.6l engine.

I've just had a look at the parts fiche and the valves are
indeed different between the CNG and petrol engines. So this is
probably no help at all... FWIW if it were me, I'd skip the additive
thingy and just drive the car, save the money you would have spent
on whale spunk and put it toward the _possibility_ of a valve job.

Then when you sell the car without having any trouble with the vales,
blow it on booze.

 

Who's that?

<confused>

"Show me your workings".

 

1ml per litre = 1000 litres of LPG to 1 litre of additive.
16,000 miles per 1000 litres = 16 miles per litre = 72mpg...

Half it, 36mpg and you're still getting 8,000 miles out of your £20-worth
of additive.

I think the technical term is homeopathy, though.

 

Interesting. I can't find any mention of differences between the
bi-fuel & petrol Mitsubishi engines, which doesn't really mean
anything. Might ask the dealer for part numbers out of interest.

That's pretty much my thoughts too. It's more the fact that it does
appear to coke the valves up that's putting me off using it rather than
the cost.

As an aside, I was very surprised to find the 2.4L Mitsubishi lump
hasn't got hydraulic lifter thingies - it's manual bucket & shim
adjustment like bikes. Which I suppose is good as it makes it very easy
to check if there's any valve seat regression.

 

That's what I made it too. If Hog thinks he's going to get 72mpg out of
his Outlander, he's going to be very disappointed! More like 25mpg.

 

Ooops I forgot the link
www.prinsautogas.com/en/products/valvecare/valvecare.html

 

Ah, so when you said 'top manufacturer' you meant 'top LPG system
manufacturer who sells the kits'. No conflict of interest there then.

Can't see any links to tests on there, so I'm sticking with snake oil
for now.

 

Top LPG manufacturer. I don't think any major car maker produces their own
equipment. Prins are pretty much tops and don't specify it for all and any
so I would give it some credence. However Mitsubishi don't fit it to the
OEM kits AFAIK therefor.....

 

I saw a Shell report on using unleaded fuel in Shite Old Car Engines,
when leaded fuel was phased out.

They took BL Series A engines as the yardstick and ran them for
something like 30k miles at 'normal' speeds before any noticeable valve
seat regression appeared.

However, they did say that if the lumps were severely hammered, the
seats were looking dodgy before 10k miles or something.

I'd just run it without the snake oil and if something goes wrong, worry
about it then.