what oil to use
 

I know it's probably been answered 1000 times, but I'd like to know what weight of oil to use for my area and driving. Hot climate year round and mostly short drives. I've seen anywhere from 10-50 to 5 - 40 or doesn't it make that much difference?

Hah! There is nothing like a good oil thread to get the juices flowing on this forum! :D

To get this started, I also live where its generally warm year round and I use Mobil 1 10W-40 High Mileage. The 10-40 should be good at warm temps and the "high mileage" components are anti-wear and seal protection additives.

Oh boy, an oil thread!

I like to use Castrol TWS 10 w 50. This NOT the same stuff you can buy at your local Pep Boys. The only place I know to buy it is at BMW car dealers. It is the only oil approved for the M3 that had the main bearing problem they fixed a few years ago.

As I understand, it has a high boron content which is supposed to be a good extreme pressure lubricant without the harmful effects of high ZDDP on the catalyst. So, I figure it should help the IMS bearing if / when oil gets in there.

As always, your results may vary...

Well after I posted this I did a search, should of done it before posting I know, but I am still a little confused. I was reading a post (actually a lecture on oil, oil 101, oil 102 ect....
Conclusion being that most engine wear occurs at start up and using the 0 and 5 -30 will protect the car as good as the higher 40s and 50s as most have the same protection at operating tempatures. The lower number supposedly flowing better at start up. I guess the old notion higher viscosity protects better is not always correct.

That is not necessarily correct as it totally leaves out several issues pertinent to start up (film strength, additive types, base polymer technology or oil “Group”, etc.). Realistically, the “W” or cold viscosity choice should factor in everything, including the ambient temperatures the car is going to see. That said, most OEM “recommended” W viscosities have more to do with their desired impact on CAFÉ mileage performance than protecting your engine. Hence, when just a few years ago the OEM’s would spec 10W-X oil for use in near arctic conditions, now they spec 0W-X oils for use in LA and Dallas, which obviously begs a question or two as to why they recommend such a thin oil.

On the higher temperature viscosity, the actual choice of weights is very germane as it directly impacts the level of protection the oil affords your engine under load conditions. Because these engines run much hotter than most owners know, XW-40 is the minimum level of viscosity you should be considering, with the “W” weight choice based upon the lowest temperatures the car is going to see. For all but the most extreme cold condition’s, a 5W-40 or 10W-40 oil would offer you the best trade off combinations. From there it would be the level of ZDDP, base polymer type, etc.

I've run 5W40 in my 2006 for a few years with great results (Red Line). Then switched to a 5W50 oil (Mobil) with slightly better results. In about 2 weeks, I am switching again to Joe Gibbs 5W40 DT40 oil (Jake Raby approved).

Just rolled over 51,000 miles. Car is ROCK solid.

My UOA's support my choices.

Modern engines have much tighter clearances than old engines. This changes the whole game.

I recently carried out a study on start up wear to support the development of our IMS Solution. The test engine was started and stopped 5,200 times in the crazy July heat that we recently had to endure. I have received the results of this study and will carry out the same study in the winter at LN Engineering in Illinois where it gets way colder than here in Georgia. The same oil, engine and car will be used for both studies.
The results of the 5,200 starts in the hot climate were amazing before and after.

I leave on a 6,000 mile R&D trip in that car tomorrow :-)

The oil used for the studies is our DT40, its all we use... Nothing else.

The results of the studies will be published in my M96 Engine Bible.

Jake, I understand that you will be releasing an updated version of the DT40 oil soon; any word on when that will happen and what the differences are?

Thanks.

I asked Jake about this a few weeks ago. Basically, he said the revised DT40 won't be ready till next year, and this planned revision is to address some of the start-up noise(s) associated with our boxer engines.

We still have to burn through another 750 gallons of the current DT40 before running the next batch.The new flavor is already developed, but currently a 5 gallon pail of it cost almost 1600 bucks!

Well, apparently a lot of the concerns over cold viscosity come down to how many cold starts that you do. I estimate that my car goes through less than 100 cold starts per year and maybe 400 hot starts per year.

At this rate, Mr. Raby's test could represent over 10 years of service from my motor. Obviously if you are using your car as a daily driver, it is a totally different application, with different concerns.

Just a couple of other random thoughts:

From the data that I have seen in the past, the API specifications on oil viscosity are rather loose. That is you can have a 10 weight oil from two different sources that have a very different kinematic viscosity, and still meet the API's broad definition of "10 W".

It seems that a lot of engine manufacturer's are basically using the lubricating oil as control oil for cam timing systems, and even cylinder shut down systems. I believe that they need rather low viscosity oil for some of these system to function correctly.

Some manufacturers would sell their soul for another 0.1 mpg benefit to meet the government CAFE requirements.

All of this seems to keep driving to lower viscosities.