'06 300C SRT8, Mobil1 0W40 vs 5W40, extended OCI?

[TheFleshRocket]

So far I haven't found a solid answer in all of my searching, so I figured I'd quit lurking and post.

My wife's car is a new-to-her '06 300C SRT8 with ~33K miles on it. The previous owner says the oil was last changed around 29K, so there's a couple more K left before the next oil change.

The no-brainer would be to follow the factory recommendation of 0W40 every 6K miles, but I'm one of those people who thinks that maybe the road less traveled could be better--I'd like to go more than a 6K OCI without compromising protection. (My wife's previous car was a 5.7L 300C and I pushed it to 10k-11k OCIs running Mobil1 EP with good results, adding about 1 quart around 7K.)

Most of the UOAs I've seen for Mobil1 0W40 show that it shears down to a (high) 30-weight after 4K-5K miles or so. That makes me a little hesitant to try to push it beyond the Chrysler-recommended 6K miles. The Mobil1 TDT 5W40 claims it is more shear-stable and has a higher TBN, so it would seem to be a better candidate for an extended OCI in my wife's SRT8 and it also boasts excellent wear protection. (Winters are generally mild--it rarely gets very far into the 20s at night and the car is garaged, so cold starts in the morning are usually above freezing. IE I don't foresee any cold start wear issues with 5W40 as opposed to 10W40.)

I've seen more than a few comments about TDT 5W40 being used in SRT8s with positive results, but have yet to actually see any of those results, much less with UOAs comparing 0W40 and 5W40.

Do you guys have any recommendations here? (I am probably going to use whatever oil goes in the SRT8 in my hot-rodded '94 Caprice wagon--it's making power close to the SRT8 and I suspect that the factory-specified 5W30 might not be the best choice for it at this point.) Thanks!

 

[buster]

I would stick with M1 0w40.

 

[HTSS_TR]

M1 0W40 is recommended for MB engines includes AMG, it should be good oil for your SRT8.

My E430 actually like thinner oil than 0W40, it currently has 5 qt M1 0W20 and 2 qt 0W40. It had PP and Synpower 5W20 the last 3.5 years.

 

[Highline9]

Rotella T6 5w40 is good stuff. I think you would be fine for a 10k to 15k.

 

[tig1]

M1 0-40 will more than protect your Chrysler engine for 10K OCIs.

 

[SteveSRT8]

I have owned my SRT8 since August of 05. Note that the manual specifically recommends 6k miles for normal service, 3k miles for severe.

Under no circumstances should the car be run for long OCI's as there are fuel dilution issues on this motor from rich tuning.

I did several oil analysis to confirm this when new. And M1 0W-40 is an excellent choice as it is factory fill on your car. You are also allowed to use M1 15w-50 by TSB.

 

[TheFleshRocket]

Originally Posted By: SteveSRT8
I have owned my SRT8 since August of 05. Note that the manual specifically recommends 6k miles for normal service, 3k miles for severe.

Under no circumstances should the car be run for long OCI's as there are fuel dilution issues on this motor from rich tuning.


Interesting. I'd read about the requirement for no more than 6K OCIs but never heard any reason why. Our previous car was an '06 300C 5.7L and I ran 10-11K OCIs using Mobil1 5W20, 5W20 EP and last, 5W30 EP. None of the UOAs showed excessive fuel, and none of them indicated that the oil was out of grade. During most of that time, the car either had an ADS Superchips tune or a Diablosport Predator tune. That said, I realize that the 6.1L SRT8 motor is in a different state of tune than the 5.7L, so what's par for one might not be so for the other, even though Chrysler also specced 6K max OCIs for the 5.7L as well.

Quote:
I did several oil analysis to confirm this when new. And M1 0W-40 is an excellent choice as it is factory fill on your car. You are also allowed to use M1 15w-50 by TSB.


Yeah, I remember seeing that 15W50 was approved.. I have been strongly considering the Amsoil AMO 10W40, as it seems like it should be more shear-stable than the Mobil1 0W40 and it's thinner when cold than the Mobil1 15W50, so hopefully cold start wear (down to maybe 20F at the lowest) won't be an issue.

 

[TheFleshRocket]

Posting this stuff for my reference, as I'm trying to decide for sure which oil to run in my SRT8 (and in my hot-rodded LT1 wagon).

Mobil1 5W40 TDT
100C - 14.5
40C - 97.9
TBN - 10.7
HTHS - 3.8
VI - 153

Mobil1 0W40
100C - 13.5
40C - 75
TBN - 11.8
HTHS - 3.8
VI - 185

Mobil1 15W50
100C - 18
40C - 125
TBN -
HTHS - 4.5
VI - 160


Mobil1 5W30 EP
100C - 10.6
40C - 59.8
TBN - ?
HTHS - 3.0
VI - 169

Amsoil 10W40 AMO
100C - 14.5
40C - 91.7
TBN - 12.1
HTHS - 4.3
VI - 164

Amsoil 5W40 AFL
100C - 13.7
40C - 82.2
TBN - 8.0
HTHS - 3.8
VI - 171

 

[TheFleshRocket]

I was originally debating between Mobil1 0W40 and TDT 5W40--the 5W40 seems to be a much better candidate for extended OCIs compared to the 0W40, at least based on how Mobil markets it.

However, I've been leaning towards the Amsoil AMO 10W40 because it's thinner at 40C than the TDT 5W40 (hopefully a little less engine wear on cold starts) and has a better 100C viscosity to HSHT ratio than the TDT 5W40 (hopefully more shear stable).

If 15W50 is approved, then the AMO 10W40 should be fine--the 15W50 is much thicker at 40C so if cold start wear isn't an issue with it, then it should be even less so with the AMO 10W40.

Anyone have any comments as to why I should go with something other than the AMO 10W40?

 

[SteveSRT8]

Any 40 w is likely ok unless you're in ridiculous low temps.

The only thing better about M1 is availability. I used Amsoil exclusively for decades and it is excellent oil.

Still use it for track days and in two very expensive motors.

 

[fdcg27]

I'd use M1 0W-40.
TDT is much thicker at lower temps than the 0W-40.
M1 0W-40 also carries certs for a variety of demanding Euro apps.
TDT doesn't.
If Mobil make one best synthetic, it would have to be M1 0W-40.
Run it 6K and get a UOA to confirm that wear is under control and that viscosity hasn't taken a hit.
In more recent UOAs of this oil, shearing doesn't seem to be an unusual problem, and all oils will shear somewhat in use, unless they are run long enough to actually thicken.
Chrysler recommended a 0W-40 fully congnizant of this.

 

[TheFleshRocket]

Originally Posted By: fdcg27
I'd use M1 0W-40.
TDT is much thicker at lower temps than the 0W-40.


The difference isn't all that huge at 40C, but how big is the difference at 0C? I haven't seen numbers for 0C. (The AMO 10W40 is thinner than TDT 5W40 at 40C, so it should be better at low temps.)

Quote:
If Mobil make one best synthetic, it would have to be M1 0W-40.


I've heard that, but haven't really seen any proof for it-IE no UOAs comparing results from 0W40 with Mobil's other oils. On the SVT forum, there's an Amsoil guy there who has done a bunch of UOAs and says that the Mobil1 EP oils are based off of Mobil's best base stock and are pretty close to on par with Amsoil's comparable oils. But he hasn't said anything specifically about 0W40.

Quote:
Run it 6K and get a UOA to confirm that wear is under control and that viscosity hasn't taken a hit.


That's what I'm going to do with the current fill, although I am not 100% positive what oil is in there since the previous owner had it done at.. an oil change place, I think.

Quote:

In more recent UOAs of this oil, shearing doesn't seem to be an unusual problem, and all oils will shear somewhat in use, unless they are run long enough to actually thicken.
Chrysler recommended a 0W-40 fully congnizant of this.


The 0W40 recommendation was circa 2005, and hasn't the Mobil1 0W40 formulation changed since then?

 

[TheFleshRocket]

I also saw this post that describes how to tell if an oil is likely to shear.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=722229#Post722229

AMO 10W40 is 14.5 / 4.3 = 3.37
Mobil1 0W40 is 13.5 / 3.8 = 3.55

So they are pretty close, for sure, and unlikely to have too much of a difference in how much they will shear, but the AMO 10W40 will still be more viscous at 100C.

But is it enough to make a difference, and how much of a difference is there in flow between the two at 0C?

 

[fdcg27]

Point by point, the 0W-40 has a considerably higher viscosity index than does TDT, so it will be considerably thinner at really low temperatures than TDT.
M1 0W-40 meets the specs for all gas Mercedes, BMW and Porsche engines sold in the US.
Neither TDT nor M1 EP claim to meet these standards.
Nobody outside of the two companies knows exactly how any Amsoil or M1 product is formulated, so be wary of claims concerning basestocks. We simply don't know how much Grp IV is used in any oil.
I probably wouldn't bother to UOA some unknown oil.
I'd probably UOA the second or third run of whatever oil I had settled on using.
Yes, M1 0W-40 has changed in formulation since 2005, but the manufacturer's certs it carries haven't changed.
M1 TDT or EP are both fine oils, and I'd use either in my old BMW.
M1 0W-40 is probably their best oil, since no oil carries more manufacturer's certs.
Now, if you find fuel dilution to be a problem with this engine, you might try G-Oil, or you might give RLI a call.
RLI oils have been shown to resist fuel dilution, and are ester based. The relatively inexpensive ester based G-Oil might be able to do the same, although the source of the esters is corn oil in the case of RLI and animal fats in the case of G-Oil.
It would be intersting were someone to run G-Oil in a known fuel dilutor and then UOA the oil.

 

[TheFleshRocket]

Well, Autozone has the $32.99 5-quarts and filter special going on, so Mobil1 0W40 wins by virtue of being significantly cheaper and a good alternative. Not ruling out Amsoil for the next change, though.

 

[dave1251]

If you want to try TDT go ahead. I have seen many applications where "European" oils where factory recommended and TDT held up very well and matched M-1 0W-40;GC 0W-30 performance wise. I do not have a lot of experience or data on Amsoil 10W-40 but given the history of Amsoil I have no doubt that it would be a fine choice.

 

[MrWideTires]

Expected it to eat a lot more gas than the 5.7, I had one for some time and averaged 14mpg, maybe 11mpg when driven a bit hard around town, plus the added cost of premium.

 

[SteveSRT8]

Interesting, since I log every gallon through my car and have since August of 2005.

Including drag strip passes and track days I average 17.5 mpg across almost 70k miles.

Certainly didn't buy it for economy, but it's pretty good when compared to any other 4 door luxury sedan with the same performance envelope.

Might want to check us out at 300cforums.com as many owners say that 6.1 mileage is VERY comparable to 5.7 in a 300 at least.

 

[TheFleshRocket]

I'm a member at 300cforums.com.

Just figured BITOG was a better place to post about oil-specific stuff--most other forums don't get nearly in depth about oil.

I'm going to sample the M1 0W40 at 6K miles and decide whether to change it or leave it at that point. I was safely going 10K-11K OCIs on my 5.7L 300C and am hoping I can do close to that on the SRT8. If I'm not happy with its performance, I'll try a sump-full of the Amsoil AFF 0W40 next.

 

[OVERKILL]

Originally Posted By: TheFleshRocket
I'm a member at 300cforums.com.

Just figured BITOG was a better place to post about oil-specific stuff--most other forums don't get nearly in depth about oil.

I'm going to sample the M1 0W40 at 6K miles and decide whether to change it or leave it at that point. I was safely going 10K-11K OCIs on my 5.7L 300C and am hoping I can do close to that on the SRT8. If I'm not happy with its performance, I'll try a sump-full of the Amsoil AFF 0W40 next.


4-wheeler/motorcycle oil????