Help with SAE viscosity numbers.

[FrankN4]

Greetings

I have been reading much but this is my first time posting. I am discovereing that the more I learn, the less I actually know.

I have been driving for 48 years, I have owned many cars from a first 47 chevrolet to my now 2008 Silverado.

The first oil I can remember was Kendall and I used a straight 40 weight, I never had an oil problem. I then switched to Castrol and I used either a straight 40 or 50 weight. Never an oil problem. I then went to 20W-50 Castrol. Next was 5W-50 Castrol Syntec. I now use Mobil 1 15W-50. I bought a new pickup in 1986. I replaced the factory fill 10W-30 oil the day I bought it with Castrol 20W-50 and now use Mobil 1 15W-50. It will soon pass 300,000 miles, no engine problem of any kind, 26-30 miles per gallon.

I bought a new Chevrolet cavalier in Decembere of 1998. I drove it home from the dealer, replaced the factory fill 5W-30 oil with Mobil 1 15W-50. It went past the 200,000 mile mark last week, never an engine problem of any kind and 28-32 miles per gallon.

I bought a new 2008 Chevrolet Silverado 1500 last Wednesday. Why would I not want to replace the factory fill 5W-30 with Mobil 1 15W-50? This is an honest question, not a statement. Would not the 15W-50 protect much better and give longer engine life as that is all I really care about? Have things really changed in engine design that a 30 weight oil protects as well as a 50 weight?

I am a retired electro mechanical engineer so I understand some of the technical talk.

Thank everyone for the responses.

 

[bmwtechguy]

It worked for you, but you might consider using specified viscosity at least while under warranty. Thinner 5W-30 oil is fine for most uses in passenger cars/trucks. For more severe service or under extremely hot conditions or heavily loaded, a thicker weight may benefit engine some. Higher viscosity may allow thicker films, but you sacrifice some flow, especially when cold. With today's base oils and additive technology, I think that thinner oils work well. Maybe start out with a 5W-30, (M1 would not be my first choice as a preference). As your engine wears some over time, you could then go to a 10W30 such as M1 high mileage, then 10W-40, then eventually to the 15W-50 when at the 2 or 300 k mile mark, if needed. You will definitely lose fuel economy switching from a 5W-30 to a 15W50. Many people are going 200k miles on energy conserving oil. From your oil preference history it sounds like you might like thick oils. The mates from Down Under would probably be ok with your choices as they tend to run thicker oils overall down there. Aehass would cringe, however.

Here's an idea- how about a 5W-40 to help you sleep at night? This would be a great compromise, don't you think? Several good 5W-40 syns out there to choose from these days. Just an idea.

 

[Pablo]

The reason your rigs lasted had more do with you actually doing the maintenance, care and luck, than oil viscosity. 100:1 you could have thrown a good synthetic 10W-30 in any of those vehicles, changed the oil every 10K miles and zipped right by 300,000 miles.

I can even argue that a SAE 30 will protect BETTER than a 15W-50, but I'm burned out right now.

 

[Quest]

what next? 80wt oil in your engine?

If I were you, I'll stick with 5W30/10W30 ILSAC GF4 oils, thank you.

Q.

 

[SubLGT]

Originally Posted By: FrankN4
........... Would not the 15W-50 protect much better and give longer engine life as that is all I really care about? ...........


Depends on how your specific truck is used. A 15W50 will not necessarily protect better than a 5W30. The only way to know for sure is to start doing some UOAs on your truck.

 

[bmwtechguy]

Aehaas-sorry about the spelling

 

[FrankN4]

bmwtechguy

The Mobil 1 5W-30 caught my attention because the 40C viscosity is 64.8, the 100C viscosity is 11.3, and the viscosity index is 169. The MObil 1 5W-30 is thicker at temperature than most 10W-30's and is pushing a 40 weight.

Mobil 1 10W-30 high mileage has great on paper numbers for 40C, 100C, VI, and HTHS, but I don't know about putting it in a new, clean engine.

I would truly love to hear your recommendations for a 5W-30 or a 5W-40. The Amsoil European 5W-40 looks really gut but the total base number is a little low.



Pablo

I am here to try to learn truths and get away from any old myths or old wives tales I might be holding on to. However, I have never had a lubrication related engine failure. I have had water pumps, fuel pumps, alternators, compressors, and even brake systems give out, but not a lubrication engine failure. I have wore engines out and chosen not to overhaul them, but have never had one break.

I have never gone as much as 10,000 miles on an oil change, I have never gone 5000 miles. I change the transmission fluid and filter every 25,000 miles on automatic transmissions. I have never had one fail. I change the gear oil in manual transmissions and rear ends every 25,000 miles. I had a transmission give up a gear and another transmission that lost the synchronizers(sp).

My truck will come up on 600 miles in about two weeks. I will change the engine oil and filter, transmission fluid and filter, and the rear end fluid and I want to replace them all with the best synthetics I can get that will give them the longest possible life.

Thanks for any and all help

 

[AEHaas]

These may help you understand viscosity, the first one is more complete:

http://ferrarichat.com/forum/faq.php?faq=new_faq_item#faq_haas_articles

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=259902#Post259902

aehaas

 

[levi]

I've only been driving for about 35 years, so I've got some catching up to do! One of the things many of the drivers in our age range have a tough time with is realizing how greatly improved PCMO's (Passenger Car Motor Oil) are across the board.

Our experiences from a couple of decades ago may not necessarily be valid today. But we still make decisions today based on our past experience.

Since working for a Shell Oil Jobber back the late 80's, and also having exposure to all the major brands too, I have been a rabid fan of Rotella T 15w40. While I still consider it an excellent oil for most any application, now I've gradually realized that any major brand API SM oil is going to be just fine. And you don't necessarily need a heavier oil than specified by the maufacturer.

Today's 5w30 oils are much more robust and shear resistant than the 10w30's of only a decade ago. And as long as you aren't going to see how far you can extend out your OCI's, you certainly aren't going to do yourself any dis-service or harm by using the manufacturer's recommended weight.

Just some thoughts for you to ponder. Keep reading BITOG. It really can be enlightening. Or maddening.

 

[mechtech2]

Using heavy oil "without a problem" does not mean the situation would not have been better with a thinner oil.
Cars will run on a variety of oil viscosities.

 

[widman]

I've got you by a year, since I started with double clutching back in the good old days on a Dodge stake truck.
As several have said, a lot has changed.
Viscosity is a fun thing to consider, and raising it can have detrimental effects. Rather than repeat it all here, I'd like to suggest clicking the link below to take you to my recent article. After about 30 pages of reading, throw your questions my way.

 

[aquariuscsm]

What would too high a vis of oil do negatively besides make your engine a bit more sluggish? In my car,30wt seems a bit thin,50wt slows it down a bit,and 40wt (which is going to be my permanent fill once I do my next oci) seems ideal. FSM says not to use anything below a 10W30.

 

[Oilgal]

It really is very hard to let go of old habits.

At the encouragement of Gary Allen, I finally filled my Mitsu 3.0 with 5w-20, and it works great in my older engine. In fact, it is actually quieter on 5w-20, than it ever was on 5w-30.

I am still keeping a close eye on things. Oil consumption is now down to zip, and I got 23.5 mpg on my last tank also. Did I mention that my Caravan was loaded with 500 lbs of extra weight, and we were driving through the mountains in 75*F weather?

Hi Dr. Haas!

Thanks for starting the whole 'thin is in' thing. Now if I could just loose 25 lbs.

 

[Gary Allan]

Quote:
Now if I could just loose 25 lbs.


The fine doctor is a consultant for Nip/Tuck Keep the weight ..get the shape

 

[Oilgal]

Thanks Gary. But I would rather drink 5w-20 than get 'nipped & tucked'.

 

[AEHaas]

My wife was upset when I told her I was going to use olive oil (RLI 0W20) in her Murcielago this time around. She hates change and she was afraid it may not run as well as the Red Line 5W20 that she has liked so much.

This Friday we took the car into work and she mentioned on the way home that she thought the engine was essentially silent, clearly less engine noise than the already quiet Red Line.

She did tell me to check the tire pressures as they are low. I have not done this yet but I can tell you she notices when they are only 5 PSI lower than normal. I cannot tell. Some people are just too darn picky.

aehaas

 

[Dad2leia]

Originally Posted By: Oilgal
Thanks Gary. But I would rather drink 5w-20 than get 'nipped & tucked'.

Now why wouldn't you want to get "nipped/tucked"? I thought that was every woman's fantasy operation, but couldn't afford.

All fun aside and throwing my 2 cents in, our Pilot specs 5w20, and I've used 0w30 its whole life, and the mileage hasn't varied since the first OC, more than tenths of a mile. By the variable stand point, that is insignificant.

I'll let you know after we pass 100K miles to see if it is still purring fine, but since we've not even hit 30K miles yet, that'll be a lot of waiting...

 

[Dad2leia]

Originally Posted By: AEHaas
My wife was upset when I told her I was going to use olive oil (RLI 0W20) in her Murcielago this time around. She hates change and she was afraid it may not run as well as the Red Line 5W20 that she has liked so much.

This Friday we took the car into work and she mentioned on the way home that she thought the engine was essentially silent, clearly less engine noise than the already quiet Red Line.

She did tell me to check the tire pressures as they are low. I have not done this yet but I can tell you she notices when they are only 5 PSI lower than normal. I cannot tell. Some people are just too darn picky.

aehaas


I wish I had your wife Dr. Haas, as mine is lucky to notice if the tires are still on while driving...

 

[Gary Allan]

It's a mixed bag. My wife is a auto-condriac. Now it's a good thing when it's something that I missed or isn't apparent in my PM routine. OTOH, if it's some "occurrence" ..then she's freaked until I find it. Let's put it this way ...if the low fuel light comes on ..she's a wreck even though she KNOWS that she's got double or triple the fuel required to get home.

This is much better than my daughters. There I would get a call that the vehicle wouldn't start ..and discover that the linings were cutting into the rotors ..the oil was low ..and the brake hydraulic malfunction light was illuminated ..oh ..and the battery was totally shot.

 

[Dad2leia]

Originally Posted By: Gary Allan
It's a mixed bag. My wife is a auto-condriac. Now it's a good thing when it's something that I missed or isn't apparent in my PM routine. OTOH, if it's some "occurrence" ..then she's freaked until I find it. Let's put it this way ...if the low fuel light comes on ..she's a wreck even though she KNOWS that she's got double or triple the fuel required to get home.

This is much better than my daughters. There I would get a call that the vehicle wouldn't start ..and discover that the linings were cutting into the rotors ..the oil was low ..and the brake hydraulic malfunction light was illuminated ..oh ..and the battery was totally shot.