On Fri, 8 Jun 2012 13:39:42 -0700 you wrote:
To Shell Tech Support
We are running the shell rotella T-5
in a 1996 mazda miata 1.8 engine with a 5 speed
We do a lot of city driving ,however on weekends it is put on some
long drives
I shortened the length of my letter for space . I did include the miles we drive city and highway and about how far and speed at each time
Below is the reply I got from shell

Hello C
Rotella T5 should not be used in a gasoline engine with a catalytic
converter. If you use any oil between changes, it will shorten the
life of the catalyst. As to oil change frequency, we always
recommend following the manufacturer's oil change schedule.

Best Regards,

Shell Technical

Interesting, i wonder what there opinion is on t-6 in turbo cars.

Have not ask about Turbos but am asking about the T-6 so will ask about turbos next
Keep in mind it may very well depend on who is answering the question for the day
I have been running tthe T-5 for nearly 30,000 miles and have seen no problems

Hello Shell Tech
>> Now that you have rained on my parade what about the Rotella T-6
>> I have a 128,000 plus miles on the car but have only been using
the
>T-5 for 28
>>000 of it
>> So can I go T-6 or would you suggest I use something else
_______________________________________________-

From: "shelltechnical-us@shell.com" <shelltechnical-us@shell.com>
>To: doc3738@yahoo.com
>Sent: Monday, June 18, 2012 10:26 AM
>Subject: Re: oil change
>
>It is true that all Rotella T multigrade products T6 and T5 and T
>15W-40 all have about the same level of Phosphorus that is higher
>that allowed in current formulations of gasoline only engine oils
>(1100 vs. 800ppm). However the levels of Phos in the oils available
>in '96 were about the same as Rotella has now and in the oil
>originally specified for the car! So you may decide to stay with
one
>of the Rotella for this reason. We would not expect any problems
>either if you choose a gasoline only oil such as Formula Shell
>synthetic or Pennzoil Platinum synthetic (or the mineral oil
>products).
>
>
>Regards,

Keith
__________________________________________________ ___________________
Hello Keith,
> Am I reading this correctly that I can stay with the Rotella
T's with very
>little problem or should i get away from them and go with the others
> I see a lot of guys are running both the T5 and 6 in miatas from
91-up to 2000
>year plus
> So enlighten me a little more if you can
> Thanks
__________________________________________________ ____________________________
Yes, you can stay with the Rotella with essentially the same risk to
your system as using the original oil. Phos levels started coming
down approx 2001 year model I believe
Keith

The oil companies cut zinc and phosphorus out of the gasoline engine oils because of federal mandate to protect catalytic converters from long term degradation of performance. They originally put zinc and phosphorous into motor oils as a last ditch effort to protect metal parts from wear when the oil film breaks down.

Which is more important to you, your engine being protected against severe damage or your emissions increasing slightly over time? Which is more important to the enviro-wackjobs that got the mandate passed? They don't care if your engine is lost. They would prefer you buy something newer with even less emissions anyway. It isn't their money.

And if you ditch the cat, you won't have to worry about the nannies messing with your choices anyway. You are a Texan. Live free.

Six
the problem is I am in one of the emission check counties that requires the cat

mytwo, I wouldn't worry about it. You will get the Catalytic Converter life expected by (all) manufacturers in the mid-90's.

" ...
They oil companies cut zinc and phosphorus out of the gasoline engine oils because of federal mandate to protect catalytic converters from long term degradation of performance. ..."

What happened is the EPA set a new requirement that the auto manufacturer must warrant (and replace if it wears) a converter for 100,000 miles. Since the auto manufacturers don't want to be replacing cats for free, and they knew that with the old additive package cat life was about 80,000 miles on average, they decided to reformulate the oil.

So the API (American Petroleum Institute) which is oil companies, their suppliers, and the Auto manufacturers came up with the lower additive solution. The expected life of a cat in a new car or truck using reformulated oil is now is about 125,000 miles.

That means you have higher wear in internal engine parts traded off for longer cat life. "Higher wear" on a new car might still be longer life than on an older vehicle due to the increased sophistication of the ECM systems, tighter tolerances with CNC machining, surface hardening where applicable, use of roller cam followers, etc. Simply put a modern motor has tighter tolerances and costs more to make. Car companies don't think twice about using processes that they would have dismissed as unnecessary luxury 20 years ago. You can buy a new (not rebuilt) motor for a 1990 GM truck at the dealer for $1400. A 2010 motor is $5,000.

My own preference with a 90's vehicle is I believe you are probably better off replacing the cat three times using a high additive oil rather than accepting higher internal engine wear.

The engines Mazda put in Miatas are a lot closer to a modern engine than many of it's contemporary peers so to be honest it might not be as big an issue than, say, someone who owns a half-ton truck from the 90's. But hopefully you have enough info to make an informed choice.

Amsoil 10w-30 full synthetic

I run synergen 00-3 weight for racing and straight 20 for street use , and i try to keep a 190 degree oil temp .

At over $40 a quart plus shipping, you'd better be very competitive on the track to justify it and not be wasting money. I'm not that good.