Hi fellow members, I wanted to check to see if it was ok to use 10W-40 instead of 10W-30. I do know that the difference is the viscosity during colder and hotter temperatures, but I'd like to know if there would be any advantages or disadvantages in using 10W-40 over 10W-30. If it helps in any way, I live in Southern California where most of the time the weather is hot. Thanks

 

i use the 10w40 and ive had my 05 for a lil over a year and it runs good feels better. not sure if it is bad or good for our engines. i like to take my car to the track and its been doing fine. my 2 cents

 

Switching to part/full synthetic is switching to a 'thinner' oil.

MOST people will recommend stepping up viscosity a tad.

N/A I use 10w40 Torco.

 

I've used it for two oil changes so far, 10w-30.. But I have less than 30K on my car....


But when I changed my oil I started the car and could feel and hear the difference before even pulling out of the driveway.


seems to hold up well. But I agree if you have a decent amount of time on your engine, you should step it up

 

What about if you have very low miles, like 18k? I'm going to synthetic. Should I go to the 40wt or stay 30 until a certain mileage?

 

I've been using amsoil 5/40 for 2 years now and I am very happy with it. No noticable change in gas mileage. I have yet to do an analysis but I'm sure the results will be good.

Why not try a 0/40 or 5/40. I would research more on the royal purple stuff.

I made the switch to sythetic at 6000mi. No worries doing it at 18k with either 30 or 40 wt.

Swiftoy

 

To answer the OP:
There is no reason to run a 10W40 in your car unless you live in Death Valley and drive your car in the dead heat of the summer there (think 115+F). Otherwise, you're likely doing more harm than good.

As for Royal Purple (RP): all the data that I've seen - especially regarding wear protection and volatility - shows RP is no better, and in many cases worse than even cheap mineral base oils. Castrol GTX (as in conventional non-syn oil) in fact showed several times the wear protection over RP. Castrol GTX is actually better than standard Mobil 1, Pennzoil Platinum, Mobil 1 EP, Quaker State Synthetics with regard to wear protection and NOACK Volatility. However, Castrol GTX performs poorly in thin film oxygen uptake testing - which ultimately means it breaks down faster than most synthetic oils and can result in sludge over the long haul. That - and the fact it doesn't work so well in cold weather. Both indicate a high level of paraffin use - think old Pennzoil and a sludgy engine. Not the oil I'd use either.
RP IMHO is garbage, and all the data I've seen to date demonstrates that.
Royal Purple is marketing and little more. The same is true for Lucas Oil. Available analysis of both product lines shows them to be substandard oils that cost a lot.

If you want to buy a decent product (and it's got to come from a local store) to impress and regale your friends with stories of motor oil with - buy Mobil 1 Extended Performance. If you want to use the best motor oil you can run in your S2000 - use Amsoil 10W30 (ATM).

Swiftoy - I'm not a fan of Amsoil Euro 5W40 (AFL) for a few reasons - the most important being it's actually one of the most volatile oils in Amsoil's product line with a NOACK Volatility rating near 9% (that's not good!) and significantly greater wear than Amsoil ATM 10W30!
It is not the best oil for a high revving motor and frankly is not a very good oil overall. It has a NOACK of 8.7% (that's too high), a low TBN of only 8, and produced a relatively large wear scar of 0.44mm in the four ball wear test. In comparison, Amsoil ATM has a NOACK rating of 5.4% (lower is better there), a TBN of 12.2 (higher is better) and produced a wear scar of 0.35mm in the 4-ball test (less wear is obviously better). All those numbers are the currently the best on the market.
The AFL 5W40 produced by Amsoil is specifically designed to meet the requirements of VW/Audi cars under the VW 502.00, 505.00 and 505.01 specs (for their TDi diesel motors and their low revving 1.8/2.0T motors... I know this because I also have an Audi A3 2.0T and have to use an oil that meets those requirements in that car... and FTR: I don't use Amsoil AFL in my Audi).
Those requirements do not benefit the oil formulation with regard to a motor like the S2000.
I currently use and will continue to use Amsoil ATM 10W30 in my S2000 as it has the absolute best mix of wear protection, stability (the lowest NOACK Volatility rating of any oil I've found), high temperature/high shear resistance, and minimal use of viscosity modifiers. It's the best oil for the S2000 IMHO. When I find a better oil... I'll let you know, because I'll be using it.
My second choice for a 10W30 is Amsoil's Motorcycle 10W30. It has slightly better wear protection under extreme conditions (a variation on the 4-ball test at higher RPM and temperatures), but is slightly more volatile (not by much - 5.8) and has a slightly lower TBN (11).

 

This oil is a NO NO for Turbos, from what I hear the oil "bakes" in the turbo.....

I use MOBIL 1, which many people have their opinions on as well, so who knows

 

Hey Slip thanks for the info. Did they change they formulation on the 5/40 recently? This is what Amsoil recommended to use. The data you provided proves otherwise. Since I am due for an oil change I will be going to the 10/30 ATM and its a bit cheaper.

Swiftoy

 

Thanks Slip. Where can I find information about the statistics that you have listed about
oil breakdown between brands, volatility rating, wear, etc.. ? I'd like to know more about the different brands of oil. I'm currently using RP 10W-30.