car engine oil extended change

Conor ) gurgled happily, sounding much like they
were saying :

>> Yea you might get a bit of extra wear, but hey, an engine will be
>> scrapped typically before its 150k mile birthday, well before its
>> expiry date.

> My mates Vectra is currently on 239,000 on its original engine and
> turbo.

I'm sure - but you forget that few cars are scrapped these days because of
engines being knackered (or body rot) as they used to be. These days, it's
usually a multiplicity of small knackered bits that kill a car. A bush or
three here, an exhaust, a couple of tyres, an ABS sensor, maybe a heater
matrix or a rad. Perhaps a windscreen or a broken tail light or a bent
wing.

One MOT fail that's going to cost £500+ on a car that's worth less than
that with an MOT.

A car engine will, indeed, typically be scrapped before it hits 150k.
Because the car it's in is scrapped.

In article . 170>,
Adrian says...

> A car engine will, indeed, typically be scrapped before it hits 150k.
> Because the car it's in is scrapped.
>
Sorry, I misunderstood the point you were making.

--
Conor,

Same ****, different day.

On Sat, 04 Mar 2006 08:56:01 GMT, "jw 1111"
> wrote:

>Hi, My car (toyota petrol 1.3) does a smallish mileage in a year say
>around 5000 miles, mainly
>on fairly short distances around town. what would be the 'time' limit to
>reasonably extend oil changes for economy reasons using a semi synthetic oil
>?
>
>I suspect a lot of people will immediately say don't economize in this way.
>However some forty years ago I had a conversation with a professor of an
>engineering college and he said engine oil does not degrade 'time wise' as
>fast as most people think ( and importantly as the oil companies would wish
>us to
>believe). So by how much time could one reasonably delay an oil change with
>modern oils?

For short trip use Semi synth does not allow extended oil change
intervals. Fully synth doesn't either. They both offer advantages to
people doing higher mileages with fully warm engines. Oils use
additives which neutralise acid build up and help keep carbon
particles in suspension, over time these degrade, stop working and
will eventually dump sludge. Synthetic oils and blends are less
dependant on additives to maintain the oil's lubrication properties
over the whole period. But it's not the life of the additive package
that limit's short trip use.

As Chris said it's contamination that won't boil off. It gets into
the oil from blow by of raw fuel and water vapour. A lot of fuel gets
past the rings during starting and warm up as it's running very rich
and fuel doesn't vaporise well in a cold engine. Your short trips
won't get the engine to full working temp, it takes about another
10min driving (not idling at lights or in stop start traffic) after
the water gauge points at normal for it to be fully warm. So you won't
boil this fuel and water out of the oil, it just accumulates. Fuel
and water are not good lubricants for your engine's bearings. Water
is better than no lube at all but fuel is very poor it washes the oil
off the bearings.

Read your owners manual for the "maintenance schedule", look for the
bit "severe driving conditions", and have car serviced as listed under
"repeated short trips". For UK use even in present cold snap you can
ignore anything about "repeated short trips in extremely cold weather"
that refers to USA East coast and continental Europe with temps below
-10c all day. Most makers consider your usage abuse and recommend
additional oil changes.
--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

> Hi, My car (toyota petrol 1.3) does a smallish mileage in a year say
> around 5000 miles, mainly
> on fairly short distances around town. what would be the 'time' limit to
> reasonably extend oil changes for economy reasons using a semi synthetic
> oil ?
>
> I suspect a lot of people will immediately say don't economize in this
> way.
> However some forty years ago I had a conversation with a professor of an
> engineering college and he said engine oil does not degrade 'time wise' as
> fast as most people think ( and importantly as the oil companies would
> wish us to
> believe). So by how much time could one reasonably delay an oil change
> with
> modern oils?

He may have been right on the time factor, but it's the short journeys that
cause a build-up of condensation, which is not good. You want to change it
more frequently rather than less. Every 6 months would be ideal, but with a
decent quality modern oil you'll probably get away with every year. But for
the minimal cost of an oil change, do it every 6 months and keep it in tip
top running order.

--
"Doctor Fox was on the panel and I asked him why we didn't even get
nominated, and he said 'because you're not very good'. <pause> At least I
don't practise medicine without a license." - Ricky Gervais on the Sony
Radio Awards

"jw 1111" > wrote in message
...

> I suspect a lot of people will immediately say don't economize in this
way.
> However some forty years ago I had a conversation with a professor of an
> engineering college and he said engine oil does not degrade 'time wise' as
> fast as most people think ( and importantly as the oil companies would
wish
> us to
> believe). So by how much time could one reasonably delay an oil change
with
> modern oils?

As the professor said, the oil doesn't deteriorate very much with time. It
deteriorates
if it is moist, or if it is overheated. Gasoline in the oil doesn't cause
chemical deterioration
as much as it drops the viscosity greatly and reduces the lubrication
properties.

And, yes, I feel it is penny wise and pound foolish to skimp on oil
changes.

In article . 170>,
Adrian > wrote:
[ ... ]
>I'm sure - but you forget that few cars are scrapped these days because of
>engines being knackered (or body rot) as they used to be. These days, it's
>usually a multiplicity of small knackered bits that kill a car. A bush or
>three here, an exhaust, a couple of tyres, an ABS sensor, maybe a heater
>matrix or a rad. Perhaps a windscreen or a broken tail light or a bent
>wing.

>One MOT fail that's going to cost £500+ on a car that's worth less than
>that with an MOT.

>A car engine will, indeed, typically be scrapped before it hits 150k.
>Because the car it's in is scrapped.

A major cause of recently built cars in otherwise good condition being
scrapped is low speed collisions--they do little if any damage to the
body, but deploy all the airbags. At $1200-$1500 each to replace, a
vehicle with six airbags could need $10,000 in repairs just to replace
them.


Gary

--
Gary Heston I don't need an iPod, I have an IQ.

A worthwhile endeavour:
http://www.thebrestcancersite.com/cg...jects/CTDSites

Gary Heston ) gurgled happily, sounding much like
they were saying :

> A major cause of recently built cars in otherwise good condition being
> scrapped is low speed collisions--they do little if any damage to the
> body, but deploy all the airbags. At $1200-$1500 each to replace, a
> vehicle with six airbags could need $10,000 in repairs just to replace
> them.

It's _very_ unlikely that a low-speed collision doing "little if any" body
damage will deploy any - let alone all - windbags.

<sees $ signs> Perhaps they're set to go off quicker in America, where
people seem to see windbags as a suitable substitute for seatbelts.

Besides, replacement airbags for my car are listed at about £200 each.

You've gotten several answers regarding the 'technical' reasons you should
change it every 6 or 12 months.

My experience -- my 5 1/2 year old Saturn just hit 30,000 miles. I've had
the oil changed a total of 3, maybe 4 times. This last change was the first
in probably 2 1/2 years and the mechanic had *nothing* to say about the
condition of the oil, the engine, or anything else. (Well, I asked "any
problems" and the answer was "no." So I guess he did say something.)

Personally, I was uncomfortable waiting that long. I think I'll be happier
on an 18 or 24 month schedule myself. But, I do put 120 miles (averaging
65-70 mph) on it one-way to the airport every few months, so it's not 100%
city driving.

I had a mechanic at a AAA-approved facility tell me that I was bringing the
car in too often for as little as I drove it (I would have been on a
once-a-year schedule at that time) so I would suggest you find a reputable
mechanic and ask them.


"jw 1111" > wrote in message
...
> Hi, My car (toyota petrol 1.3) does a smallish mileage in a year say
> around 5000 miles, mainly
> on fairly short distances around town. what would be the 'time' limit to
> reasonably extend oil changes for economy reasons using a semi synthetic
> oil ?
>
> I suspect a lot of people will immediately say don't economize in this
> way.
> However some forty years ago I had a conversation with a professor of an
> engineering college and he said engine oil does not degrade 'time wise' as
> fast as most people think ( and importantly as the oil companies would
> wish us to
> believe). So by how much time could one reasonably delay an oil change
> with
> modern oils?
>
>
>

It's the other way around. Your driving falls into the 'severe' range
for oil changes. Follow the book on that timing.

The short trips contaminate the oil with unburned gas and condensation.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

jw 1111 wrote:
>
> Hi, My car (toyota petrol 1.3) does a smallish mileage in a year say
> around 5000 miles, mainly
> on fairly short distances around town. what would be the 'time' limit to
> reasonably extend oil changes for economy reasons using a semi synthetic oil
> ?
>
> I suspect a lot of people will immediately say don't economize in this way.
> However some forty years ago I had a conversation with a professor of an
> engineering college and he said engine oil does not degrade 'time wise' as
> fast as most people think ( and importantly as the oil companies would wish
> us to
> believe). So by how much time could one reasonably delay an oil change with
> modern oils?

Adrian > wrote:

>It's _very_ unlikely that a low-speed collision doing "little if any" body
>damage will deploy any - let alone all - windbags.

There is a video on the net somewhere of a guy in a sports car having
to stay stopped at a light while a little ol' lady with a shopping bag
slowly crosses in front of him. He rudely honks his horn at her, and
she in turn swings her shopping bag, hitting the front of his car.

*POOF* His airbag deploys in his face, and she continues walking
across the street. Dunno if it was a setup or not, doesn't look like
it, but funnier than H anyway.