Kind of a stupid question but ive been putting 5w30 mobil full syn in my car(cobalt 08 ss tc) i was buying oil today and the guys keeps referring to there 10w30 since i have 90k miles. Is this a good idea? Or i should just stick to 5w30

 

Stick to 5w-30. 10w-30 isn't any thicker per se than a 5w-30.

the 10w refers to cold weather "protection" and its a moot point

I wouldn't even consider going to a 40w on this car until 200k miles honestly.

 

If you are buying synthetic oil, 5w-30 will give you better cold start protection over 10w-30 as the "w" is the winter rating of the viscosity of the oil at a specific low temperature. Because it is synthetic oil, excess additives are not required for the oil to have a wider viscosity range unlike conventional oil. This makes it so 10w-30 synthetic has absolutely no advantages over 5w-30 synthetic. The last number is the oils viscosity rating at operating temperature so both 5w-30 and 10w-30 will have the same viscosity at temperature where as the 5w-30 will perform better until the oil warms up. Along those lines 0w-30 will give you even better cold start protection, better flow at lower temperatures and the same viscosity at operating temp as 5w-30 and 10w-30. If you wanted to run a heavier oil you would need to go to Xw-40.

 

I'm at 104k and I'm using 5w30 Mobil one synthetic just like recommend

 

Just stick with 5w30. Modern car engine tolerances are pretty close, not like engines that were made 30 years ago, and they do not need a heavier weight oil as they get older. The only thing putting a heavier weight oil in the car will do is get you less gas mileage. The only other reason to change oil weight is if you are in an extremely hot or cold climate.

 

Good advice guys- if I drove mine in the winter I would probably run 0-20 in it due to cold starts being very hard on an engine and not running it hard in the winter. But it gets put up so I don't have to worry about it.

 

Thanks guys! The oil was on special maybe thats why the guy was pushy with the 10w30. But anyways thanks again

 

There seems to be a consensus everywhere to not use Mobil anymore but switch to castrol, valvoline or something else. just sayin. I have no theoretical or statistical evidence to back it up but some say the quality has gone down or it doesn't really offer the same protection as it used to etc.

 

I haven't heard anything about that to be honest rice

 

I know that Powell suggested going to Mobil 1 Extended Performance for the better additives.

0w30 also works well too. I have used it a lot.

 

Prob those VW boards you're now frequenting. Don't use Castrol.

 

I think this has to do with in the U.S. they made a change that you can legally classify oil "full-synthetic" when it actually contains some Group III oil. Actual full synthetic oil is group IV or V. From what I understand is Mobile "full-synthetic" is now not pure Group IV like it apparently used to be and actually contains some group III. It is a pretty well guarded secret apparently but some Mobile 1 oils are still full group IV like their extended performance, racing oil, and euro spec oil. But this is just stuff I have found on the internet and has not been verified.

 

Castrol synthetic oil is fine oil, it's a low ash oil that meets the specs put out by GM, VAG, and others. Until you get full oil analysis or a used oil analysis on your specific car you can't make don't use claims for certain brands.

That being said, OP just keep running 5w-30 Mobil 1, if you want to switch to extended performance feel free. Although I do strongly recommend getting a few used oil analysis to determine how the engine is doing and how the oil is performing in the conditions you put it through.

 

Subaru guys HATE Mobil 1 5w-30. but our motors destroy 30w oil like its nobody's business. its not considered a full synthetic anymore. Its a group 3 which is still decent quality. but Amsoil, Redline and Motul are all group 4+

 

I did have an Amsoil 5w30 test done at 7,500 miles of use and it was still very good. Would go 10,000 easily with a filter change every 5k.

 

I run 0w-40 Amsoil in my built motor and it runs great. So far 3 good UOA on 3k OCIs.

 

I got back a good UOA for Mobil 1 last summer before switching to Amsoil. My drive is mostly commute and there were a number of pulls and tuning included on the UOA.

 

I always got good results with m1 High mileage on the LNF. Blackstone even told me to push it out to 10k.

 

I believe the VW forums are eating away at your brain cells....

My oil analysis with Mobil 1 extended performance have always come back great.

 

I know a lot of people running around with 150,000 on their motors always using Mobil 1 and they still don't smoke. Not saying there aren't other quality oils out there but I wouldn't be afraid of m1. Like anything else if you drive it like you stole it and expect the motor to always take it, you may have figured wrong...

 

don't listen to stupid store guys. tell the store guy I said so

 

I run Mobil1 in my Cobalt AND both VW's.

 

If it meets the spec I run it. I'll pick up almost any major brand oil. Whatever's on sale.

 

I run Mag 1 full synthetic by Warren Distribution. It's cheap as hell on Amazon. Like $28 for 6 quarts. Had a Blackstone analysis done on it and it did exceptional. 8K miles on the oil change in the SS/SC and they recommended extending the interval to 10K with it due to how well it did.

Before I found Mag 1, I did what cluelessk did. Just bought whatever was on sale. Really no such thing as a bad oil anymore unless you buy from Dollar General

 

There is some truth to this statement. Pretty much all synthetic vehicle oils sold in the US are Group III however they are a modified Group III oil that contains and has some characteristics of Group IV oils. Valvoline, Castrol, Mobil, etc, which are sold in the US all do the same thing. They don't just do this because it is cheaper, because it really is not, but because a true Group IV oil does not mix well with anti-acidic additives and can cause gasket and seal corrosion. The manufacturers have found that they get much better longevity and less engine wear using Group III bases in engines.

Trust me, if the oil manufacturers thought they could charge $25 or more a bottle for true Group IV oils AND show that it was better for your engine they would be doing it.