Centrifugal oil filter

It will have negligible effect on engine longevity. That is not the purpose of a bypass filter. It is to facilitate the safe use of very long drain intervals in conjunction with suitable oil.

Huw

I see where you are coming from, in effect in the absence of this equipment long drain intervals cannot be used as the oil and filter bung up with particulate?

Once the oil is filtered to this high degree the limit on oil life being build up of chemicals which the oil can no longer neutralise and loss of lubricity from long chain molecules being broken up?

I have extended the drain interval on my lpg powered V8 to 15K miles, the oil remains golden and from an old posting to an lpg list I hope the oil still remains in spec. No signs of problems yet, and I do drive it set very lean as this increased economy by ~5%. Mind I am very envious of the lpg mileage Martyn reported from his 4.6 grumble, which should be heavier than my 110 by some degree, I take it it is the gearing that makes use of the better characteristics of the 4.6.

AJH

Yes. The bypass filter actually filters much finer particles than most standard full flow ones. These finer particles do not cause wear until they saturate an oil to a large extent and overwhelm the oil. Take these out and the limit of the oil is greatly enhanced.

Huw

does the filter also work to hold sulpur particals/ I use the Land Rover in north and west africa and i know the diesel overthere is not 'that good' Higher level of sulphur, so I change the oil every time I get back from a trip (driven ~10000 km per trip) Is the change necessay, what do you all think?

regards Fred (Holland)

"Huw" schreef > > > >

In general terms, if fuel sulphur levels are above 0.5% then the oil should be changed twice as often as listed in the normal service schedule.

Huw

LPG powered vehicles require *more* regular oil changes. The oil stays clean looking because there is significantly less carbon produced by the combustion of LPG however a relatively large amount of acidic byproducts are created. These acids stay in the oil and attack bearing surfaces within the engine. I would suggest a maximum 5K mile service interval for a LPG powered vehicle.

This was not the experience of the chap that ran a medium term test on this, having the oil regularly sampled and tested. The oil remained in spec such that the extended change interval could be used.

If you can cite a reference to why lpg should produce more acidic oil contaminants than petrol I may delve around and see if I can find the site I referenced.

I can see running lean will produce more acidic products (principally dissolved NOx) when on full power but do not think lpg differs from petrol much in this respect.

AJH

On or around Sun, 10 Oct 2004 21:55:28 +0100, snipped-for-privacy@despammed.com enlightened us thusly:

and if it's properly set up, it shouldn't be running significantly lean anyway.

I've noted that the oil stays clean, and more to the point, stays "feeling" right. I still change it anyway at 6K, same as for petrol - the vehicle does some miles on petrol, and in any case, the extra cost is minimal. For the same reason, I don't follow the modern practice of changing the filter every other oil change - the filters cost about a fiver, so why not put a new one on with the new oil - the one that's done 6K miles can't be all that clean.

Can't cite it online - and can't find the printed material at the moment, although the head of automotive engineering at the local trades school (who agrees with me) is going to look out a copy for me.

AIUI part of the problem is the higher combustion temperatures of LPG help break down the additive package in the oil more quickly which reduces it's ability to neutralise the acids.

OK. Have a look at this

Which was put up from a guy on the lpg list in 2001, it seems to point to the opposite, plus commercial lpg is also lower sulphur than petrol (0.02% IIRC).

From the earlier bits of this thread it just might be that oil in petrol engines is life limited more by particulate saturation than loss of detergent or lubricant properties.

AJH

I doubt mine is properly set up as it is a simple system, I have previously posted how the mixture probably leans out as the coolant gets hot. I am sure I run it lean though and it has been worth a few mpg at the cost of lousy pick up.

Fine but one of the reasons I could justify the lpg conversion over buying a diesel was that I could extend the oil change interval, to save pence per mile compared with a diesel.

I imagine now, some 5 years on that this would not be the case as modern diesels have long change intervals, better performance and good economy.

AJH

>

On or around Tue, 12 Oct 2004 13:39:01 +0100, snipped-for-privacy@despammed.com enlightened us thusly:

I'm under no illusions about it, I could run a diesel one for similar money. In fact, the main thing the V8 gives me that a diesel one wouldn't apart from slightly better performance (and mine ain't running lean - not at average 13 mpg) is a nice noise.

You can't make a convincing case for LPG being cheaper than diesel. You can however make a case for it costing about the same. Considering specifics, and comparing a 300 TDi disco with my 3.5 V8, to get the same performance as the V8 I'd have to up the boost slightly on the TDi and increase the fuelling accordingly, and maybe fit a bigger intercooler. There remains also the finding of most that the 3.9 engine gives similar economy and a bit more performance, or a bit more economy with the same performance.