Changing oil weight from 5w-30 to 0w-40???

Judging from the data i have with 5W-30 and 0W-40 on the 308GTS Qv here, you made a GREAT move. The 0W will lower startup in <cough> cold Florida weather. The 40 weight will be good to bring up the hot pressure. i also use Mobile 1 and played around with various oils over a few month period. For Florida daily driving and maybe a touch of spirited 0W-40 is fine (but not for pure track use).

 

Use 0w-40 Mobil 1 in both 348 and 308. No problems.

User manual calls for 10w-40 anyway. May run cooler and better oil pressures with 0w-40 than 5w-30.

 

What weight do you use for track?

 

I recently switched to Mobil-1 0-40W. Originally I tired to use a 5-30W when I bought the car last year but it was too thin for my 88 328 GTS. Burned up a couple of quarts very quickly. Went to the 40 weight and it's been great. No problems!

 

Just to note 5w30 and 10w40 are probaby one of the worse oils you can use in conventional oils. The reason is that in order to get the wider (30 point) viscosity difference they use polymers. The polymers are what cause break down and cause sludge. The same would be true about 20w50 but since it already starts at a heavier weight it doesnt require as much polymers to get to that weight. I have always used 20w50 in all my performance cars, new engines or old. Infact some new cars void the warrenty if you use 10w40 just for this reason.

 

I switched from Mobile1 15w50 to Castrol TWS 10w60 for my BB512i and immediately noticed that the engine ran quieter. The TWS is hard to fine, but well worth the effort IMHO...

 

using oil with a 50 point split is probably the worse switch you could of done

 

Just to chime in here also. Are you referring to new normal cars?? The new cars we have here,for the last few years only reccommend using the 5-30,10-40 and 15-50 weight oils. Engines these days are built with tighter machined tolerances and they need the "lighter" viscosity engine oils to protect the engine. And to help with fuel economy also(2nd most important thing these days they reckon? ) Im not saying that you cant put any "thicker" oils in your enigne,cause you can and it will not pose a problem. Maybe get a small increase in fuel economy,but thats about all really.

 

I'm assuming he's referring to non synthetic oils.

 

Thinner oils are fine for new cars the problem is with the way oil is made. In order for oil to have a wide span of viscosity they have to use polymers. Nothing wrong with polymers in small amounts such as in 20w50, but with 10w40 they have to use alot more. lets take 5w30 as an example, this oil is really just a 5 weight oil. Then they add polymers, when the oil is cold the polymers curle up and allow the oil to flow in its normal state, when the oil heats up the polymers unwind in long connected structures, this causes resistence making the oil thicker. Great idea but polymers are not oil. Polymers can burn, tear, wear, shear, and melt, and this is where the problems begin, and why you shouldnt use it any performance engine

 

Qucik case in point,we used to work on a low mileage 2000 Subaru WRX and conducted our own little oil experiment! Hehe We used to use Shell ECO-10 (10-40w) recommend by Subaru.After taking an oil sample, we changed the engine oil and oil filter and refilled with Shell Helix Standard (20-50w) We let the owner take it away on holidays for 2 weeks,covered around 6000km in that time. He brought it back,we took an oil sample and then changed the engine oil,again using the 20-50w. We sent him on his way and we sent both oil samples to Shell Australia and they "annalysed" the oil samples. For a cost of $30 each. I forget the exact technical words that Shell used in the oil sample report, but it showed that both oil samples had around the same amount of "wear" particles in the oils ect......... alll that crap and that it would reccommend either oil the WRX. LOL And it did use a little more fuel on the highway than normal he said,but nothing to get excited about. After the 2nd oil change with 20-50w,we went back to the ECO-10 oil. Now that ive bored ya's with this oil crap,please continue! LOL

 

Thats why you use fully synthetic oils in performace engines.Im sure them guys will be using fully synthetic oils when they made the swap?

 

Amsoil 20W-50 Synth 2000, but the oil temps get high at over 115C on warm track days! Viscosity is also a function of temperature so the higher 50 weight is MUCH thinner at higher temps than at cold startup.

i can;t believe we are getting into another oil debate guys...

Anywho, will be removing the stock oil cooler for a B&M with built-in fan that kicks in at 160F to lower those temps and may try 10-40 if i feel confident about keeping temps below 100C or so at the track event.

But i am sure others here will yell at me for doing this and say i am going to blow up the engine, etc etc. My car, my engine, car will never be for sale...

 

The local Motul tech is trying to convince me to try their 0W-20 race oil. It's what they run in the WRC. Having started with 15W-60, I'm not prepared to make such a big jump, but he insists it will be perfect on the track, along with freeing up some extra power.

 

It wouldnt be much of a power increase would it stephens? Maybe get a few oil leaks instead?? hehe

 

LOL!!

 

For a good overview of motor oil, you can read Ali Haas's "Introduction to Motor Oil" at http://www.focfloridaregion.com/edu/oil.htm . It will clear up a lot of misconceptions about the oil you should use.

 

Have you read it all?

 

I havent got a spare 10 hours to review that. Maybe you can elaborate for the boys? That looks like a lovely colour on your 348 by the way

 

On my BB512i the oil temp seems to run at a little below 100c regardless of the outside temp., although it does take it 30+ minutes to get up to that temp. The water temp on the other hand will run 85c or so during the winter and 90c to 95c during the summer depending on how hot it is and whether I am in stop and go traffic or on the highway. My oil temp did drop a little once I started using the Castrol TWS 10w60 as compared to what it was doing with the Mobile1 15w50 I was using.

 

I thought Hass's post claimed lighter oil would remove more heat. I have always been a fan of heavier weight oils, and everything I have ever read said heavier would run cooler. Thats why they run 70 weight in F1 cars. And anyone who thinks different should go do some searching. I read one article where they hooked up an oil heater to the Ferrari F1 car and transfused it with warm oil before starting the engine.

 

Oh gosh, i already typed this in the oil thread a few months back. Please use SEARCH function. Thanks.

 

Where can you buy Castrol TWS 10W-60 beside the BMW dealer?

-Peter