http://www.bobistheoilguy.com/visc.html

Look at the SAE grade column. Something that is classified as a 30 weight (like a 0W-30, 5W-30, 10W-30, etc) will have a 100°C viscosity between 9.30 and 12.49 cST (centistokes, a measurement of viscosity - higher is higher).

http://theoildrop.server101.com/ubb/...c;f=1;t=009433

That is a link to a thread with standard info of TONS of oils. M1 5W-30 (I assume the old SL formulation - the new SM might be a touch thicker) has a 100°C viscosity of 10.0. So like you and I were saying, it's on the thin side for a 30 weight.

40 weight has a 100°C viscosity range of 12.50-16.29. M1 0W-40 is 14.3, so it's doing a little better in its range than the 5W-30 is. Have fun comparing oils!

 

just a few tidbits of info on why you should stick with your synthetic...

+synthetic oils are superior to dino oils in part due to the ability of the polymers to not break down as quickly. these polymers are what help create your viscosity spread. thus resulting in the ability to go longer intervals without chainging the oil. petroleum oils tend to break down immediately. synthetics oils can last for many thousands of miles without any significant reduction in performance or protection.
+synthetics are superior due to burn off reasons. dino oils are a refined product containing molecules of varying sizes. as petroleum oils are heated up, the smaller molecules begin to burn off. deposits and sludge are left behind to coat the inside of your engine. as the smaller molecules burn up, the heavier molecules are all that stays behind to protect your engine. since the larger molecules do not tend to flow nearly as well, they only exacerbate the heat problem as friction builds up. synthetic oils are designed in a lab for lubrication purposes and are comprised of molecules that are of uniform sizes and shapes. therefore, even if synthetics do burn off a little, the remaining oil mantains the same characteristics that it had before the burnoff.
+synthetics have a much better film strength. film strength of an oil represents its ability to maintain lubrication between moving parts as pressure is applied. synthetics have a much higher film strength than petroleum oils do. so a lighter weight oil that provides for good low temperature protection can still provide good protection during high heat, high load conditions. this will reduce engine wear. less engine wear produces less oil contamination. less contamination produces longer engine oil life.

i have a few other webpages that discuss synthetics in great detail. any info wanted, lmk. also, invest in a good air filter (cotton reusable filters cost more and produce good airflow but dont necessarily equal good protection) and a good oil filter (not fram...)

 

Guys, this advice is good. I can't tell you how much it makes me laugh when I hear people fussing about 2k oil changes with synthetic, but they'll happily run a K&N air filter or even Fram oil filter.

 

I Also Recomend Amsoil Oil That Last 1 Year Or 20k Since I Only Drive 10-12k Per Year It Works For Me For A Full Year Just Change My Oil Filter At The Midle Of The Year.

 

I rest my case.

 

BOBISTHEOILGUY is a GREAT site to read up and learn about all the different oils out there...

To the guy who asked why M1 0w40 instead of M1 5w30 or 10w30, do a search on this site (or especially www.LS1tech.com or www.bobistheoilguy.com) for a guy with the username of Patman. He has done many oil analysis test of used oils (including the different Mobil One brands as well as German Castrol 0w30, etc.). The results for LT1's & LS1's showed much better with the M1 0w40 vs the other Mobile brands stated. GC 0w30 has showed the best results that he has seen vs many other brands tested. He's even posted them up many times on the boards, so they'll show why. If this stuff is good enough for him w/ the LT1 & LS1, than it is good enough for me. I trust the actual results rather than differing opinions...

 

Thanks for all responses, especially the links with actual evidence. Looks like I will be trying replacing M1 5W30 with M1 0W40 in the next oil change!

 

To safely do this you need to analyze your oil. Yes Amsoil(and a lot of other synthetics) can last that long BUT if they get dirty they are dirty period. You leave dirty oil in no matter how good it is you are still basically extrude honing your bearings. A top quality oil filter is also in order a cheapy like a Fram is unlikely to last to 5K without internal damage to the filter. Little things like a filter change with the accompanying fresh oil can greatly extend how long the oil itself lasts, the little shot of fresh stuff does a lot more good than you would think.
On the K&N air filters some guys report very little dirt(silicon) in their oil others end up switching back to paper filters to get numbers down. Personally I don't think I would try to push a K&N equipped vehicle to 10K and beyond without testing. I alss suspect that they people who report very high dirt numbers with K&N filters might have been overly rough cleaning them in the past.

Another thing to consider is that the Caprice for instance the owners manual states that the change oil light may not come on till 7000miles, and this car was dino filled and that was the dino of 10 years ago. Yes we here run our cars harder than that but if 10 year old dino was good for 7K of highway usage then todays synthetics are capable of FAR FAR more than the #k everyone wants to drain them at even under hard usage, provided of course you keep them clean.