adam_

Couple of thoughts.

TWS 10W60 (yes, TWS is Ten W Sixty) is a BMW product- made by Castrol but specific for BMW. It is limited in distribution, previously only via BMW channels. It would be expected that Porsche would not even consider this for certification.

TWS is a fine oil, but it it rather heavy. As a relative guide, here are the hot and cold viscositities:

.....................40C........100C
M1 0W40........80........... 14.3
M1 5W50 .......87.6 ......... 17.4
TWS .............163 .......... 24
M1 15W50 .....125 ...... 17.4

If you like TWS, then you gotta love 15W50... just based on these specs.

I'm just posting this as a data point. Discussions of oils are universally .... interminable.

A

ltc

IIRC, RL member 'T2' (Tom) has the highest mileage 996TT in this forum...went past 200K a long time ago.

wross996tt

Ummmm...yes I know this...I was playin' with macster....LOL

jcb-memphis

If it were my car, I'd change it. Just me.

jeff

Macster

Various mentions of cold start emissions from a variety of sources. I don't have any at hand to quote from but I'll look through my files.

Also, I know the EPA constantly checks both new cars (supplied by the various auto makers) and older used cars (sourced by a company that specializes in obtaining from various sources (private individuals) to constantly monitor total vehicle emissions, from cold start, hot start and run, hot soak, etc. in order verify not only are emissions that are produced when engine started and run within limits but emissions (vapor mainly) when car just sits are within acceptable limits as well.

Sure, a cold start followed by a 10 minute drive (and my experience in even mild ambient temperatures that 10 minute drive at moderate (city) speeds may *not* have my Boxster or Turbo engine up to full operating temperature) is almost all done with a cold engine and emissions are quite a bit higher. If one looks at real time fuel consumption it is quite a bit higher than when the engine is fully warmed up and more fuel consumption translates into higher emisisons.

The engine controller is in open loop mode and thus not required to deliver a stiochiometric mixture to the engine (a mixture which is more suited to the converters in that the exhaust gases arising from this mixture are more thoroughly processed into less harmful emissions). Also the converters are cold and unable to process exhaust gases much if at all so a stiochiometric mixture would be of no use and in fact a negative. Why? Cause it would be too lean (approx. 14.7:1 air:fuel) and this not rich enough to heat the converters as fast as is desired. Also, it is too lean for a cold engine.

A cold engine receives a richer mixture and the engine's idle speed is raised to provide heat to the converters to get them going. In some cars secondary air injection systems provide excess oxygen *after* the exhaust ports to help burn the unburned fuel -- the result of an on purpose overly rich air:fuel mixture -- and provide heat to the converters so they can begin processing exhaust gases.

As soon as the converters are hot enough and the O2 sensors begin to deliver meaningful numbers the engine controller then goes closed loop and from then on (except in well exceptional situations -- hard acceleration being one) the engine controller feeds the engine the stiochiometric mixture that the engine turns into an exhaust gas the converters are designed to process.

If cold start emissions not a big concern auto makers/engine designers would not bother to fit engines with secondary air injection systems. God knows these systems are responsible for more than their share of problems.

More recently secondary air injection systems have been replaced by variable valve timing and lift that the engine controller can take advantage of to feed excess oxygen to the exhaust system.

Modern DFI engines are set up to inject fuel *after* the combustion is finished -- during the exhaust stroke even -- to put some raw gas in the exhaust gas stream where it will combine with excess oxygen to speed up the heating up of the converters.

No engine maker, car maker would go to this trouble and expense if it didn't have to.

Less friction due using a lighter oil at engine start a good thing, sure, but not at the expense of inadequately protecting the engine at cold start or any other time from metal to metal contact and accelerated wear.

One has to be careful and realize that more and more auto and auto engine design decisions are being based on the requirement to meet ever more tighter emissions.

Now if a new engine is being designed various features can be selected to meet the the tighter emissions in a mechanically safe manner.

However, with older engines, they are what they are. Their lubrication needs were determined/set at their time of design and manfacturer and for some engines their lubrication requirements change as they accumulate miles and experience some wear.

However, pressure on automakers drives them to imho make oil choices that are questionable from the point of view of the engine.

Similarly market forces are leading many auto makers to substantially cut back on scheduled maintenance. Mike Miller who writes a very good tech colum in a BMW magazine rightly calls it global war on maintenance.

New vehicles still should have the maintenance, but to make higher new car costs less painful BMW and other car makers are cutting back on scheduled maintenance. The thinking is they want to avoid the issue of after selling someone a very expensive automobile telling the customer oh by the way you need to bring the car in after 2000 miles for an oil change. This does not go over very well with the customer.

Actually the customer should consider any dealer/car maker who advises this a good dealer/car maker one that has the customer's total car ownership experience in mind, not just the brief experience shortly after buying the car.

This is probably one of the best things one can do to a new engine but market pressure rules over sound internal combustion engine maintenance.

And more and more automobile magazine writers/reviewer praise (!) automakers that have ever extended servicing intervals and comment negatively on those few automakers that still advise a new car engine have an early oil/filter service.

Sincerely,

Macster.