Makes good sense. I have a X5 that I put less than 10K miles a year.
Mostly stop and go driving. The Oil Service Indicator never goes to
orange; however BMW does an interim "low usage" oil change. Even so,
the oil (after about five months and 2K miles) looks dirty. I realize
"looks dirty" does not mean anything technical. However, I am tempted
to do an oil change anyway. Yes, I realize it is my money and if I
want I could go ahead and change the air in the tires too.
On that note, I read about a service station that is pumping pure
nitrogen (99%). Charges $7 per tire. Is that also another gimmick or
is there any sense to it?
There is some sense to it. Dry nitrogen has (obviuosly) no oxygen or water
vapour in it.
Oxygen can attack the rubber, causing some degradation over time. However,
this happens to the outside of the tire no matter what you do, so minimizing
it on the inside doesn't hurt but probably doesn't help much.
Nitrogen is a slightly bigger molecule than oxygen, so it diffuses through
the rubber more slowly. All other things being equal, a nitrogen tire will
loose pressure slightly less slowly than an air one. But air is ~78%
nitrogen anyway, so that's also not a huge effect.
The biggest one, as far as I know, is change in pressure with temperature.
Air contains some amount of water vapour, which apparently changes pressure
with temperature more than straight nitrogen (I don't know how the
thermodynamics behind that work). In theory, a nitrogen filled tire will
maintain pressure more evenly than an air filled one.
I suspect this whole idea got piggy-backed off the airline industry, which
does fill their tires with nitrogen. But they do that because, if they use
air, the tires will explode under certain situations. No car tire operates
that hot, so it's not really applicable.
Actually, Dave, that's not accurate. If you go Google "Toyota oil gel"
you'll find a bunch of stuff. Now, Toyota says it's people going beyond
the oil change intervals. However, Toyota also says 5K miles for heavy-duty
use and 7500 miles for light-duty so owners often don't know which regime to
follow. It's clear that oil change intervals matter, but what the interval
be is a matter of conjecture.
BMW is conjecturing (with good reason IMO) that 15K miles synthetic
changes in their engines is adequate. If you could answer the question:
"why 5/7.5K for Toyota and 15K for BMW", you would have my
Of course, one reason would be the quantity of oil used: Toyota
uses only 3-5 quarts while BMW uses 7-8. But that's probably
not the only reason; the Toyota critics allege that since the gel
problem only occurs in specific engines it's a design fault that
can be masked by frequent changes.
Bottom line: there's no hard scientific evidence that changing
oil at 15K intervals in BMWs is best for long engine life.
So where's your evidence that cars serviced by the indicator suffer
reduced engine life? Despite reading a lot about BMWs I've not read anyone
reporting engine problems down to worn out or contaminated oil. Which
would surely be common if it *were* three times the 'correct' amount. And
the BMW service indicator does take into account the type of usage which
fixed intervals don't.
*It's lonely at the top, but you eat better.
Dave Plowman firstname.lastname@example.org London SW
My 2 cents:
With today's modern engines and lubricants, it's unlikely an engine is going
to "wear out" during the warranty period regardless of whether the owner
follows the factory recommended oil change intervals or has it changed more
often. After the warranty is over, the manufacturer wants you to buy a new
If you are trying to get 2 or 3 times the warranty life of an engine, then
changing the oil more often makes sense. If not, you are wasting your
But I don't buy new cars and often run them well beyond any warranty. My
last BMW was at approx 150,000 miles when I sold it (E34 525 24 valve) and
that was in rude health. The 'specialist' that bought it from my dealer
clocked it back to 70,000 so must have thought so too...;-)
My previous one, an E28 520, now belongs to my brother and despite a hard
life towing is approaching 250,000 miles. The bodywork will see the end of
that car - not the engine. It's still sweet and burns no oil.
IMHO there are very very few people who buy a car new and run it to high
miles - apart from business users. And business users are the ones long
service intervals are aimed at. If service intervals are marginal you're
bound to increase the overall failure rate. Exactly what business users
*'Progress' and 'Change' are not synonyms.
Dave Plowman email@example.com London SW
Only if the oil degrades significantly between the change intervals. If
your synthetic provide sufficient protection at 10,000 miles, then changing
every 8,000 will make absolutely no difference to your engine life.
The engine "wears out" due to loss of metal. That can happen chemically or
by metal-to-metal contact. Chemical attack is a function of how well the
oil neutralizes contaminants...that does decline with age, but there's a lot
of factors that play into that that are more important than just age.
Metal-to-metal contact is a binary thing...you either have it or you don't.
If you don't, then it doesn't matter if your oil is brand new or 15,000
The oil does suspend metal particles that have come off the engine.
However, if the filter is working properly, none of the particles in the oil
are big enough to damage anything, so who cares?
and the small particles that are too small to be captured by the filter, but
do discolour the oil, float harmlessly withing the film of oil as they pass
through bearings, which is why the colour of the oil is unimportant unless
it varies from the norm for that engine at that service interval. Anyone who
has ever had and maintained a diesel engine will know this.
A diesel's oil gets black within a few hours after changing it. Typically
an oil analysis is done from time to time to indicate abnormal wear of the
engine. (This is the case of marine diesels, anyway ... I don't know about
Hardly anyone bothers with cars. They just change as indicated in the owners
manual. As you say, the oil in many diesel engines gets jet black with dirt
within minutes [no exaggeration] of changing for fresh oil. This is quite
normal and doesn't stop diesel engines living a long and productive service
Even my old indirect injection land rover diesel engine lasted over 22 years
until last night when it finally expired with a bang. Its oil always had a
filthy dirty appearance yet it lasted over 12,000 operating hours which
amounted to 140,000 miles of short journies, many towing up to an illegal
five tons [allegedly;-)] while carrying a ton payload. Not bad for a 67hp
2.5 old technology engine revved to the governor routinely.
The USA has been slow to embrace diesel power compared to Europe. In fact,
for several years the emission standards for diesels were such that no
diesel powered new cars subject to emission testing were available from US
or European manufacturers. Within the past couple of years new models that
meet the emission requirements have become available. I became a believer
when I purchased my first diesel powered boat and now drive a diesel pickup
truck as my daily driver. Ultra-low sulfur content (15 ppm) diesel fuel
became mandated here in Oct (replacing the low-sulfur fuel of 500 pmm). It
definitely burns cleaner and I've noticed that the occasional "whiff" of
diesel exhaust smell has completely disappeared.
Yes they have removed the aromatic compounds as well as sulphur. A
by-product of reducing sulphur is, as you say, less soot through the exhaust
and combined with direct injection engines, less soot in the oil as well.
This is partly the reason that some European diesel engines can run far
longer between oil changes than petrol engines from the same manufacturer.
For instance, some VW and GM diesels can go for up to 30,000 miles between
oil changes. Yes, its worth repeating for those that change their oil every
3000 miles, 30,000 [thirty thousand] miles between oil changes.
I haven't yet read the Toyota oil thread either, but you did say the ref was
to drivers exceeding the recommended interval.
With my 1986 W123 230E (ok, ok, a Merc, but same difference...) I followed
the (fixed) recommended intervals and it ran fine for 120 000 miles and 6.5
years till I had to ret rid of it (my company decree). Continued fine
service until one of the subsequent owners bent it beyond economic repair.
For direct contact replace nospam with schmetterling
"Floyd Rogers" < firstname.lastname@example.org> wrote in message
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