I'd like to get opinion on using Shell Rotella T 15W40 in a performance (450 hp) motor. It seems with my forged pistons having a .008 clearance, etc. that 10W30 is too thin and 20W50 seems too thick, especially when cold. The 15W40 seems to be a good compromise. I know Rotella is used mainly in desiel engines but on the container it claims to be approved to gas engine use too. Maybe a 20W50 synthetic would work also. Opinions?

Well Hell , I just back from a weeks worth of schooling provided by my employer , It was Basic Engine Class and delt with much much more then Basic Ill tell you we covered Engine oils ectencivly , first off useing a Diesel Engine oil would be a very good choise I cant go into all the tech reasons but if you look at the API <American Petrolium Institute> rateings you will see somthing like SC and CH-4 , C is diesel engine oil and S is automotive engine oil ,, diesel engine oil is made to withstand much more punishment then (S) automotive engine oils ,, now some Automotive engine oils do have a API C rating which is a plus ,, chosie a oil that has both S and C ratings as for the wieght of oil , think about the temp range you live in, the W in 15W/40 oil stands for WINTER , which means the API has tested the oil at 0 degrees F and at O degress F its at 15 wieght and the 40 means API has tested the oil to be at 40 wieght at 210 degrees F this rule applys to all multi wieght oils ,, now a SAE oil like SAE 30 is rated at 210 Degrees F only and is not for cold weather ,, as far as the best oil you could use it would be a synthedic oil like 5w/50 or 10w/50 in your case ,, you want your oil thin at start up as that is the worst time for your engine and you need the lube pressure there as fast as possible and the oil will thicken to 50 wieght when your engine reaches 210 F. if you run at 180 degrees your oil should be someware between 40 and 50 wieght , we have taken synthedic engine oil samples and had them tested at 6,000 miles from company trucks and found that the samples were in excellant shape , testing is still going on to see when then best time to change the oil but as it stands with a synthedic oil you can easly go 6,000 plus with no more then a oil filter change , I know this ancer is a long one and my spelling isnt the best , just thought I would share what I have learned , BTW this school was instucted by Caterpiller Co. and the do have the $$$ for R&D ,, I hope I have helped you in your decision , Cya John
oh ya WARNING!!! do not use a Fram oil filter , the instructor had us cut open several filters and Fram is by far the worst , it is VERY cheaply made and I would not put one on my lawn mower!!! ,, good oil filters are Wix,Hastings,AC,Cat,Donovan,Purotator,Napa ,,these are the ones we cut open I was told Quaker State oil filters are just as cheeply made as Fram so stay away from them ,, I wish I could show you what a Fram oil filter looks like inside, it would make you laugh and I am not kidding http://www.chevelles.com/forum/smile.gif
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John
Catapiller Mechanic
Salinas,Ca
70SS 454 Clone {in construction}

[This message has been edited by catman (edited 02-25-2000).]

[This message has been edited by catman (edited 02-25-2000).]

Well, filters can be a whole thread in itself. Frams are bad, check out this link:
http://minimopar.simplenet.com/oilfilterstudy.html

some good info on filters. I personally use NAPA Gold.

I've sat lurking on the sidelines for a long time now, .....
but i just had to ask ,
what oil thickens as it gets HOTTER? (I must have been using the wrong oil all these years)
http://www.chevelles.com/forum/wink.gif

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Jeff
Fort Dodge, Iowa
ACES #2814
Team Chevelle #21
www.dodgenet.com/~jmee/71chevss.html (http://www.dodgenet.com/~jmee/71chevss.html)
jmee@dodgenet.com



[This message has been edited by JPM71 (edited 02-26-2000).]

None, its just that the wider range oils don't thin as much as they get hot. Wide range fossil oils are not a good idea but not an issue with synthetics so a 5W50 synthetic is just fine a 5W50 conventional oil, if anyone made it, would be junk.

DO NOT USE DIESEL ENGINE in gasoline engines, All the additives in diesel are meant for diesel applications only. The 20W20 is straight 20 all the way, even at high temps. Mostly used for summer driving in everyday applications. And who would want a car thats viscosity increases as the tempature increases? (viscosity=thickness). Oh yeah, your setup sounds good (15W40) but if synthetics are thinner oil, try 20W50 maybe?

Ok , next time I see my instructor I will tell him he does not know what he is talking about and Ill write the API who supplyed the books we used in class and let them know that they are wrong in there thinking that additive packages in the oil do not increase viscosity (thickness) of the oil at 210F in a multi grade oil,, damm I guess I waisted my time in class http://www.chevelles.com/forum/smile.gif
AND.... there is no additive in diesel oil that can do anything but help your gas engine , period ,,, unless , maybe my instructor was wrong again?
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John
Catapiller Mechanic
Salinas,Ca
70SS 454 Clone {in construction}

[This message has been edited by catman (edited 02-26-2000).]

Hi guys,
All multi weight oils increase in viscosity as the get warmer. a 10W30 oil is the equivalent of a 10W oil at 0 degrees F it will also never get any thinner than a 30W oil will at 100 degrees C or 212 F Here is a couple of good links for more info on oils and oil pressure.
http://vger.rutgers.edu/~ravi/bike/pages/pages/docs/oil.html
http://www.melling.com

By the way RPM, your forged pistons only have .008 clearance when they are cold. As they expand they will close up to probably around .002 or so depending on the piston manufacturer. Also, not all forged pistons are made the same, there are quite a few out there that are made out of a low expansion materials. They only have .002 or so cold, they just dont expand much.
By the way, you never really said why you think the oil you are running is not "thick" enough ??? Is it because of the piston noise when cold, or is there an oil pressure problem. Piston clearance really has nothing to do with oil pressure. 10w30 should be fine unless there is some problems with bearing clearances etc. Send some more info, maybe we can figure it out.
Hope this helps,

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

[This message has been edited by BillK (edited 02-26-2000).]

It is my understanding that motor oils do have add-pacs to increase the viscosity as the temp gets hotter and thin out as they get cooler, or at least work to protect your engine in this manner. As far as diesel oil is concerned, I wouldn't use them! They do have high EP (Extreme Pressure) ratings but they do not have the same add-pac that is required for gasoline engines. For example, you may get more cylinder wash down with rotella than you would with a straight 30w oil. Rotella oil has a high ash content and will "Dirty" your engine and create sludge quicker due to the lack of its cleaning properties. Diesel fuel is basicly kerosen and has a lubricating property within itself for lubing the top end of the engine, thus requiring less of its engine oil. Also diesel engines turn much lower RPM's than gas engines and their oil is designed to protect them at these RPM levels and no more.
I may be out on a limb, but that's the way I was told. Also, I WOULD NOT use a 50w anything because it puts undue stress on your engine componets due to it's thickness. IMHO

Synthetic oils have a higher EP rating than Fossil oils. Stick with what the manufactures recommend. Sure, we can say their in ca-hoots with each other, but then again maybe the millions of dollars they spent on R&D were actually spent on Martini's. http://www.chevelles.com/forum/tongue.gif

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Lowered '67 Elcamino
ZZ430HP / 4L60
"Canyon Carver"

[This message has been edited by Cardiac (edited 02-26-2000).]

MOBIL 1 nuff said

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John Krenn
1970 malibu SS look-a-like well kinda
350/200-4r (soon to be 383)

Ft.Worth, Tx

Straight 30, call me old fashioned if you will, just don't call me late for supper. As for the F@-#m filters (no bashing here), I saw a warranty get voided once because of one. The customer at the dealer where I was working brought a car in with an engine that had died due to oil starvation. We fixed it the first time under warranty, and showed him the service bulletin from the factory that warned against using F#!-m oil filters. Less than three months later, he was back with the same problem. It seems he went to Wally Mart and bought the same F-&#m oil filter, removed the the one we installed when we rebuilt the engine, and slapped the F&@--m filter right back on, in spite of the service bulletin that he read right in front of our service manager. This time, the district rep himself stepped in and said no dice to a warranty repair

Oil does NOT become thicker as it heats up and does not get thinner as it cools. This is common sense. The numbers don't mean that a 10w-50 oil has a 10 weight at 0 degrees...or that it has a 50 weight at 210. It means that at 0 degrees the oil acts like what a straight 10 weight oil would look like at 0 degrees...and at 210 it acts like a straight 50 wt. would at that temp. Multigrade oils still get thicker in cold weather, they just don't get as thick as a straight grade would.

I've been working with Caterpillar engines for a number of years. Ours are D399's and put out 1200 HP to 800KW generators. They always run at 1200 rpm because that's how we maintain 60 Hz. electrical frequency.

We changed last year from Texaco Ursa 40 wt. to Royal Purple Dezel Hi Base 40. The difference was noticed immediately in performance, temperature reduction, and wear. (We also test oil samples at regular intervals.) I run Royal Purple 5w30 in all my vehicles.

I understand that they say multi-vis oil is thinner when it's cooler and thickens as it heats up. I don't know how true this is. It can be easily tested using a small funnel. Hold your finger over the bottom of the funnel and fill it up with cold oil. See how long it takes to flow through. Then fill it with hot oil (using something other than your finger) and see how long it takes to flow through. This will give you a good idea of how the viscosity changes.

I agree that 50wt is too thick for almost anything. I used to run 30 in winter and 40 in summer. Now I run 5w30 synthetic all year and have no lubrication problems.