question on thicker oil.

[Jessed87]

Here is my question. I am installing a down pipe soon so I am going to try to prevent the smoking issue before it starts. I already have a catch can installed so next I am going to switch to a heavier weight oil. Now I see a lot of people suggesting a 5w-40 oil. Unfortunately I have been to many auto parts stores and nobody sells any 5w-40 oil AT ALL. It is only 5w-30 or 10w-40. I figure it will be okay to go with a 10w-40, which brings me to my next question. Correct me if I am wrong but I have heard that the 2 numbers in the oil are cold engine oil viscosity for the first number, and warm engine for the second number. If this is true, then how would an oil that is the same viscosity at start up as the recommended factory oil solve a smoking issue at idle during start up? Maybe I am thinking to far into it, but I am still curious. I also realize that my chances of preventing the problem all together are slim but I am all for doing what can be done to try to prevent it. If I have my facts wrong, I would appreciate constructive responses please. And as usual, thank you for any and all assistance!

 

[Wurf]

Here is my question. I am installing a down pipe soon so I am going to try to prevent the smoking issue before it starts. I already have a catch can installed so next I am going to switch to a heavier weight oil. Now I see a lot of people suggesting a 5w-40 oil. Unfortunately I have been to many auto parts stores and nobody sells any 5w-40 oil AT ALL. It is only 5w-30 or 10w-40. I figure it will be okay to go with a 10w-40, which brings me to my next question. Correct me if I am wrong but I have heard that the 2 numbers in the oil are cold engine oil viscosity for the first number, and warm engine for the second number. If this is true, then how would an oil that is the same viscosity at start up as the recommended factory oil solve a smoking issue at idle during start up? Maybe I am thinking to far into it, but I am still curious. I also realize that my chances of preventing the problem all together are slim but I am all for doing what can be done to try to prevent it. If I have my facts wrong, I would appreciate constructive responses please. And as usual, thank you for any and all assistance!

Over all temperature ranges, 10 is the runniest or least viscous it should ever be and 40 is the thickest or most viscous. Imagine if it's 20 below outside, the oil should flow the same as straight 10 weight oil at that temperature. Imagine if it's 100 degrees outside, the oil should flow the same as straight 40 weight. For summer operation it might be fine. Cold starts in cold weather, I'd want the 5W30.

I spoke with a service adviser at a Mazda dealer today and he said it was very important to follow the owners manual in regards to selecting the proper oil. That said, the 5 in the 5W30 isn't what's coming into play when your car is idling after it's warmed up, it's the 30. Going to 40 MIGHT help.

Words from my profession as a tech, I would only change ONE thing at a time.

 

[Rotus8]

The additives that make the wide viscosity range are the most fragile in the oil package, and hardest to do. 5w30 is already pushing it, 5w40 is very difficult if not impossible to do, and will have a very short life.

 

[MSMS3]

The additives that make the wide viscosity range are the most fragile in the oil package, and hardest to do. 5w30 is already pushing it, 5w40 is very difficult if not impossible to do, and will have a very short life.

+1

And it's the additives that give out first if you try to extend the mileage between changes. So even though good synthetic oils hold up to heat and stress so much longer, the additives still give out just as quickly as in dyno oil. So, irrespective of claims of much longer service intervals, it's not prudent to go much beyond 3,000 miles before changing oil and filter.

 

[ElGaspo]

FWIW: walmart used to carry Shell Rotella T, which is fully synthetic 5w40, but they quit carrying it- or at least the ones near me have...wally world still has the regular Rotella which is dino juice 15w40. rotella is truck oil and there's a lot of good talk about it: diesels are DI and produce a lot of soot, both of which apply to the MS3.

since i wanted full synth, i had to drive a bit but found 4 qt jug of Rotella T at Auto Zone for $20, which is the same price as walmart when they had it. so far so good, but i only put 200 miles on it. no way i'm driving in stop-n-go traffic in summertime florida w/ only a 30 weight...(sun)(sun)

 

[UHATEIT]

EZlube did mine 2 weeks ago and put in 0W-40 Mobil 1 which they said they usually use on Audi and other european cars. I went with that since they said it was a bit thicker and could protect the turbo seals cimilar to the 5W40. No complaints thus far

 

[LBV]

Wurf - 10w40 is fine in the summer ... come winter if you still can't find the 5w40 just go with the 5w30.

 

[Jessed87]

Alright, I think I will go with the 10w 40 and just keep the oil change intervals at 3000 miles as I have been. Thank you for all the info. and suggestions guys, and feel free to post any more info on the topic.

 

[Wurf]

Just got my first oil change at 2300 miles via the dealer. Not even kidding when I say it has made a noticeable change in the way the motor sounds and the smoothness at idle. They put Motorcraft 5w30 semi synthetic in the crankcase.

I will change it out for Valvoline synthetic 5W30 at 3K and that probably won't be until August or Sept.

 

[MSMS3]

I am going to make an observation and at the same time also plead ignorance of an important detail regarding engine design. My family is in the production engine rebuilding business and also does custom performance engine work and machine shop operations for local "speed" shops.

When Ford first came out with the "Modular" 4.6 and 5.4 L OHC engines, they specified a 5W30 oil, and then a 5W20 as an alternative. It was hard to find these oils and many people ignored that recommendation. We started seeing engines show up with oil related failures just outside of warranty. Upon inspection we were finding that the bottom end of the engines were being oil starved. We wondered why. About that time, our trade organization, Automotive Engine Rebuilders Association (AERA) issued a technical bulletin based on data collected from Ford, pointing out that the low end oil failure had been traced to use of higher viscosity oils.

It seems that there are very tiny oil passageways in the cylinder heads for oil return to the crankcase. This was an intentional design related to the needs of the overhead cam and the cam bearing journals in each cylinder head of those engines. Higher viscocity oil was not thin enough for the oil to pass freely back from the heads through the block into the lower engine to feed the rod and main bearings.

Accordingly oil was pooling up in the cylinder heads causing the lower engine to be oil starved resulting in main and rod bearing journal damage.

Having said that, I have no idea if there are very small bore oil passageways in our engines, either in the cylinder head or in the block. But before I would abandon Mazda's recommendation on the bottom number for oil viscosity, before I'd increase the top number, I'd think twice. There may be engineering design considerations that are more specific than our general appreciation of what oil viscosity range works best in various climates at different times of the year.

I'm running catless DP/RP. I run a pure synthetic, but keeping it at the recommended 5W30 viscosity range.

 

[Wurf]

For reasons mentioned above regarding oil passages, I have read of similar problems with Nissan VQ35D with non-oem spec viscosities and I have no intentions of changing from 5W30 for either of my cars.

 

[tru-boost]

Thicker oil wont save you.... sorry

 

[jengajoe]

The Aussie manual says you can use higher viscosity oil. (friday)

 

[LBV]

Very good points made MSMS3!

As stated directly above though, the Aussie manual states they can use the 40 grade oil and this also came from an "insider" at Mazda Canada where they stated 10-40 in the summer is fine but back to 5-30 in the winter.

 

[Wurf]

I want to run the thinnest oil I can that still provides adequate protection. The increased mileage the MFG seeks with thinner viscosity is a direct result of reduced parasitic losses and friction. This also means increased HP vs thicker oil, although I won't guess how much that would be.

Personally I would only consider going thicker as a last resort, such as if you already have a catch can and are trying to eliminate smoke from leaking seals in the turbo etc.

 

[MSMS3]

Another thought for consideration:

Some of the "other boards" including ones with more general discussion of performance turbocharged engines in general, are reporting that the size of the oil return line from the turbo back to the crankcase is actually contributing to the pressure problem with the turbo seals, finding that many turbos (including the K04) have return lines that are too small to allow the oil to return to the crankcase without buildiing up excessive pressure inside the turbo and leaking past the seals. On tear down, the turbo seals are normal.

Now, I don't know if this is true. But if it is true, increasing viscosity is only going to make things worse and not better, if the objective is to reduce seal leakage, it would seem to me, because the heavier oil will increase line pressure.

There is some experimenting going on to increase the return line size in various applications. Those who are doing this are reporting that the turbo "smoke" is greatly reduced or gone. All this is purely anectdotal as far as I'm concerned, because I don't have any solid proof that this is the issue with our K04's. But I know that in the turbo performance world, turbo oil return lines being undersize is a serious topic of discussion.

Those who have some credibility in the performance turbo world seem to be addressing the "smoking turbo" issue with changes in the PCV system (catch cans and second PVC valves) on the intake side, and with larger oil return lines from the turbo. Both approaches make sense to me. I don't think heavier oil viscosity is consistent with either one. Just my opinion.

 

[Wurf]

Word

+1

 

[Bonafide_Spd3]

For 10w 40 mobil 1 says its for cars over 75k miles. I saw one that was 15w 50 for track cars. I didn't know which oil to get, I've been putting 10w 30 extended performance oil by mobil 1. What would be good for florida weather